Transcript for:
Comprehensive MCAT Chemistry Review

hey everybody welcome back to the channel so today I want to review through all of the general chemistry that you need to know for the MCAT I got a 100 percentile on the MCAT about two years ago and this was actually my primary source of studying was the miles down review sheets it's a really fantastic resource for learning pretty much everything you need to know for the MCAT um I think it is very helpful to be able to sort of be able to put all the information together know a little bit more additional information structure all the information and so that's what I'm going to do today is try to show you images and explain every concept so that you know everything you need to know for the upcat all right um how I recommend you get through this video is you pause you rewind you take notes um make sure you understand every concept uh as we're going through it and I'll just be asking questions um as we go along just to make sure that you understand the concept and if you can um answer the question immediately then you probably know the concept if not then just pause the video and just keep going so the first thing we need to know is uh what these uh symbols mean and so the a is the mass number the mass number is the number Pro protons and neutrons and the Z is the atomic number and this is kind of the number that defines what um what Atom we're looking at and so that's the number of protons now we can have isotopes and Isotopes is when there's a different number of neutrons an example of this is carbon 12 carbon 13 and carbon 14 each carbon has six protons which is again the defining feature of the carbon the atomic number um but it has either six seven or eight neutrons and so that will be the mass number 12 13 or 14 now if we take the percentage uh of the um the percentage of the carbons that are in the state of 12 13 or 14 and we weight the averages of them so if there's 99% carbon 12s uh 0.5% carbon 13s and 0.5% carbon 14s then the weighted average is going to be very close to 12 just a little bit above 12 and so if we look at a periodic table over here you can see that if I look at Carbon again carbon the mass number is usually 12 13 or 14 the atomic number is six and the atomic mass is 12.011 and we get that number from averaging the sum from summing up the mass numbers and multiplying them by the percentage at which they're found in nature all right so that's that now we're going to look at the scientist contribution so the first thing is Rutherford model and this is in 1911 and he basically did this really cool experiment where he found that he took these alpha particles which were radioactive substances and he shot them through a gold foil really really quickly um and so what he expected is that almost all of the alpha particles would move just straight through this gold foil and leave a little print on this um on the sheet over here and so what we were expecting is that we see this little dot over here and what he actually saw is that um majority of the dots were right here straight through but we actually found that it deflected more often than he was thinking deflected um 5% of the time it doesn't really matter that you know the number but he found that you know this is what he was expecting which was the Thompson model which was the existing model which is that you know um the atom is just this ball with a lot of different particles all around but he actually found that there must be some solid mass in the middle that's resulting in this deflection and this solid Mass must not take up a lot of the space it's mostly empty space and has a solid mass in the middle and that's the nucleus so that's what Ruther figured out okay the next thing is the bore model which was actually just two years later um and he found out that let's look at the bore model model so basically he found out that these um electrons exist in these energy levels like Nal 1 Nal 2 Nal and he tested this with hydrogen and he found out that um when an electron goes from an Nal 3 or Nal 4 like a higher energy state to a lower energy state it actually releases light right and so he said that you know the Ruther model is correct that there's a nucleus in the center and that there's these electrons that exist at energy states and they travel around the nucleus and so that's kind of what the bore model said and he said that photons are emitted and when the electron goes from a high state to to a low State and photons are absorbed when an electron goes from a lower state to a higher state and so this is actually pretty close to what the reality is um but you know what we ended up figuring out is that uh these electrons don't exactly live in this this state but it actually kind of there's a probability model where an electron can exist in any area within uh a defined place um so it might be a sphere around the nucleus and the electron can be found usually 95% of the time within that sphere or it might be like a p orbital and you might find the electron 95% of the time within that space but you can't actually know for sure where the electron is and that statement that you can't know where the electron is for sure is the Heisenberg uncertainty principle which is that you can't know the momentum and the position simultaneously and I was always really confused by this concept but um somebody explained this to me really well which is that momentum you should just know is where the particle is going and position is where it is and so if you you can basically take a snapshot of the atom and you can figure out where is the electron right now but you can't also know where it's going and so that's why the bore model is incorrect in that specific case where you you don't actually know that this electron is going like a planet in a circle around the Sun around the nucleus actually there's just a probability that you know that it's probably going to be within the space but you don't know exactly where it's going to be at any given moment and you can't if you do know that then you can't also know where it's going to go and so that's kind of the Heisenberg uncertainty principle how I think about it is if you had a camera and you're taking pictures you can know where it is but you can't know where it's going and simultaneously if you know where it's going you can't know where it is okay the Hun's Rule and I'm going to open up the periodic table again hun rule is let's say we take something like um nitrogen right nitrogen has uh two protons and it's sorry two electrons and it's s One S 2 two electrons and it's 2s and then three electrons and it's 2 p we'll get through this a little bit later but uh to stick with me and so we know that there's two electron three electrons sorry in its 2p orbital and if there's three electrons in the 2p orbital what Hun's rule says is that all three of the electrons are not going to be in the same um space it's actually going to fill up like if we I'm just going to go down a little bit if we look at um sorry but okay we'll get to it later but if we basically look at how the electrons are distributed uh what we'll see is that it's kind of like these electrons are distributed within the 2p so each one takes one of these little orbitals rather than both of them pairing up in the orbital before taking up empty space this is because electrons don't like to be together they repel each other and so they only start to fill up again once there's a fourth fifth or sixth electron within this 2p um I hope that makes sense okay the last one is poly's exclusion par principle and we just say that no electron has the exact same four quantum numbers that's exact that's basically what poly's Exclusion Principle is and so obviously we have paired electrons in these 2p 3p 3D in all these orbitals we have paired electrons but we say that the paired electrons one of them must be a plus one2 and the other one must be a minus one2 this is kind of just a convention thing um but that's kind of what we call the spin on the electron okay there's some constants that you need to memorize for the MCAT the first one is avagadro's number which is 6.022 * 10 23rd the second one is planks which is 6626 X 1034 and the third is speed of light was 3 * 10 8 and you don't actually need to know 6.022 you kind of if if you know 6 * 10 23 that's fine too U make sure you know what the units are so av's number is just a number you don't actually need there's no units to it but we say that that is equal to one Mo so when we say one Mo of carbon what we're saying is that we're taking 6 * 10 23 atoms of carbon uh if we say planks constant you kind of just need to know 6.6 but it's good to kind of I I just know all all the digits um because they just keep showing up in questions um but for calculation purposes if you just know the 6.0 or 6.6 you're probably going to be good in terms of the MCAT these are also equations that you should memorize not too difficult um they're both actually the same equation eals HF um and we know that frequency sorry that frequency times wavelength is equal to speed and so we know that the speed of light is and so if we know what the frequency is we can figure out what the wavelength of that light is and if we know what the wavelength is we can figure out what the frequency is okay this is planks constant so if you multiply planks constant by the frequency we get the energy and again if we take take the uh speed of light and divide by the wavelength we get the frequency so these are just the same equations okay the next thing we need to know is quantum numbers quantum number is four different um terms for defining what an electron is that's uh orbital orbiting the nucleus the first thing is the the principal quantum number and it labels what shell number or energy level that the electron exists in so the electrons in hydrogen and helium are in the first principal number or the First Energy shell the electrons in nitrogen for example which is what we were looking at before is in the second energy level and you can kind of see that you can see what the energy levels are so the first number here three this 3D everything here is in the third energy level okay the next one is um oh also I guess another thing that you should know is that usually these match up with what row they are that is true except for these D and F so 2 s and 2 p are in the second row so you can kind of know what the principal number is but from here it it starts at 3D even though it's in the fourth row so you should just know that okay next thing is the L which is the azimal uh um quantum number you don't actually need to know these names but you should know what these letters are um and this is the 3D Shape of the orbital so this is what I was talking about before is this is the probabilistic U model for where you think that the electron is going to be 95% of the time so if if it's in s orbital then you know that it's going 95% of the time it's going to be within the sphere and we can figure this out because if we take a lot of snapshots of the of the atom we can figure out where's the electron 95% of the time that doesn't mean it's always going to be there sometimes it might be way far away but 95% of the time the electron is going to be within the space same thing with P it's going to be somewhere within this space and D is going to be somewhere within that shape I can't make it with my hands and F similar thing okay so uh you should know that uh the possible values is between 0 and N minus one zero refers to S orbital 1 P 2D 3F 4 G uh you never really deal with G orbitals uh in the case of the mcap you can go up to an F orbital okay um ml is the magnetic uh name and that's when you get the orbital subtype and the integers can be between negative L and L so if you're dealing with um a p orbital you know that the p orbital is L equals 1 so the magnetic numbers can be between 1 and 1 so 1 0 and 1 and you should know that each orbital subtype can contain two electrons so that explains why a p orbital has six electrons because it contains negative 1 0 and one which is three orbital subtypes and each orbital subtype contains two electrons I'm going to repeat that again so you can figure out how many orbital subtypes there are by taking the L the L is dependent on which orbital you're looking at and you can count how many orbital subtypes there are you can multiply that by two because each orbital subtype has two electrons and if you can do that then you'll get the number of electrons that that orbital contains so let's take D for example D is two for l so you know that the number of orbital um subtypes is -2 1 0 1 2 so there's five which means that contains 10 electrons you can see that here this is 10 long which means that there's 10 electrons within the 3D orbital okay the last one is electron Spin and this is where the poly Exclusion Principle comes in and that refers that for any one of the paired electrons within an orbital subtype there has to be a plus one2 and a minus one2 um spin number on it okay um these are some handy formulas you can actually figure this out without knowing these formulas it's okay if you don't know it but the maximum number of electrons in a shell in a in a shell is 2 * n^ 2 so in this shell this shell is called this shell has a principal number of two so the electrons that it contains is 2 * 2^ 2 which is eight and if you count this 1 2 3 4 five 6 seven eight that that's true and if you do it for three You' figure out that it's actually 18 and so if you do this 2 6 8 + 10 18 yep so that's how you figure that out and then the maximum electrons in a subshell is 4 l+ 2 okay so we can figure out how many are in the D orbital which is 4 * L which is what is l l is 2 so 4 * L is 8 plus two is 10 so again we figured out that there's 10 in here all right um pause if you don't understand anything make sure you understand everything um yeah and the next thing is a free radical free radicals are atoms or molecules that have an unpaired electron um okay uh yeah and then the the next thing that we're going to talk about is diamagnetic and paramagnetic this is actually a pretty simple complic uh concept but a complicated term diamagnetic all the electrons are paired and it's if you have an external magnetic field this atom which has a paired electron which has all paired electrons is going to be repelled but if you have one or more unpaired electrons then it's going to be pulled in and that's called paramagnetic um uh yeah again follow Hans rule Hans rule says that you don't you double up only if all the electrons have filled up the orbital subtypes um uh and then you can figure out if it's paramagnetic or diamagnetic so 1 S2 is helium helium is right here it's going to be di magnetic because all the electron orbitals are filled up with both electrons now carbon carbon's right here is paramagnetic because even though it has this two in this p orbital you know that those P that that those two electrons are in different orbital subtypes because of the Huns rule so make sure you understand that okay the last thing is the off principle and that just kind of says in which direction do you add the electrons and so you can kind of or sorry in which direction are you having n plus one value so you can kind of go in this diagonal manner 1 s one uh 2s 2p right and you can kind of go in this diagonal manner to know how do you write this and so you know that um uh like for example uh what's a good one to talk about okay so this is a confusing one which is that after 3p is not 3D but 4S and that basically tells you is that if you list all of these diagonally the one two 3 four five six and you write SP PDF and you go in this diagonal manner this is basically off power principle you can actually figure out what is the increasing energy uh levels and so it's kind of confusing but but the 3D according to this is higher energy level than the 4S because right after the 3p is the 4S and then you go to the 3D similarly after the 5S is not 5p but it's actually 4D and so you can kind of figure out what is increasing energy levels based on these orbital subtypes okay next we're going to go through the periodic table which is a pretty important concept it's actually very simple uh as long as you kind of memorize a couple of things so the first thing you want to know is what is what and so you know that this is an alkal metal hydrogen these are all non-metals I'm so sorry erase what I just said so these are all alkaline metals lithium through francium the hydrogen is a non-metal that's important to know so everything in column one is an alkal metal Except for hydrogen which is a non-metal these are also all non-metals okay the halogens are also non-metals but they're the they're the last column before the noble gases so you should know that everything here are non-metals right if you look at my cursor all the bright green the halogens and the noble gases the darker green are all metalloids and I kind of remember what the metalloids are because they're kind of in a stair step pattern so the Boron the Silicon geranium arsenics uh the I don't know what this is right but if you kind of go in a stair step pattern here you can besides the carbon you can know that these are all the metalloids okay all right so again these are all metalloids in the stair step pattern the carbon uh the nitrogen oxygen fluide neon all of these are all non-metals the hydrogen is also a non-metal sorry about that mistake and all of these are alkaline metals okay in this bright orange these yellow Are alkaline earth metals and so these are all metals these are also Metals we call them transition metals and we call these post transition metals okay okay so as long as you know that these pretty much are all metals right all of this I'll use my marker so all of this is Metals right this is a non-metal these are all nonmetal and this stuff is all metalloids okay all right next thing is that these are all called Rare Earth metal rows so you're not going to find them too often a lot of them are actually only synthesized in the laboratory and then this is actually pretty high yield for information the effective nuclear charge is the pull between a nucleus and a valence electron and so you can actually figure this out based on where in the period IC table you are and so if you think about it these are all pretty intuitive if you understand the concept which is that um the pull between a nucleus and a Vance electron is going to be highest when you have the most protons in your nucleus and the veence electron is the closest to the nucleus so as you go down right as you go down the veence electrons start to get further and further away because they're in higher and higher energy States right the N number is increasing but as you go to the right the number of protons in the nucleus is increasing and the electrons are still staying at the same distance from the nucleus right so that basically defines all of these Trends is that generally as you go to the right right as you go this way these numbers are going to increase and they all kind of represent a very similar thing which is kind of like this pull between the nucleus and veence electron now they have minute differences and it's kind of useful to know these minute differences the effective nuclear charge is how how hard does the nucleus tug on this outer electron and obviously something like fluoride is going to have a very high nuclear effective charge because there's a lot of protons in it and it's not that far from the nucleus okay um the next thing is how much energy do you lose the ionization energy when you lose an electron when we rip out that electron how much energy is is being lost right and so all right I'm going to repeat that again because I I made a mistake so the ionization energy is how much energy does it take to make this atom lose an electron okay so if you're fluoride it's going to take a lot of energy to make yourself lose an electron the reason for that is because fluoride again has a very high effective nuclear charge it pulls on its electron pretty hard so it's going to take a lot of energy for this electron to be able to escape fluoride whereas this right here I think it's uh let's see I think it's francium francium is um down here where the proton number is relatively low right 87 protons in the nucleus but the electron is pretty far away right you can say that see that this is 1 2 3 4 five six seven energy levels so pretty far away so this this nucleus is not going to be able to pull on this veence electron that much so it's not going to take a lot of energy to be able to rip this electron out of the out of the atom so that's why the ionization energy is low here and high here similar to electron affinity electron affinity is how much Affinity does an electron have sorry does the all right I'm going to make a make a quick adjustment so electron affinity is how much energy do you add when you add an electron into this atom so if you look here electron affinity is the energy change that results from adding an electron to a gaseous um atom so fluoride the associated energy change is - 328 KJ per mole so to add a electron to fluoride it actually wants the electron and so this is a very important concept so to continue the electron Affinity when you add an electron you can see that there's some energy that's released and that energy is referred to the electron affinity right okay so why does it make sense that fluoride will have the highest electron affinity well fluoride is just one step away from the noble gas and so it really wants to get to this very stable configuration and so it has a lot of protons the protons are pretty close to the electrons and so so to add one more electron they would really want that to get to this next level to this noble gas configuration okay so it's this is kind of important but a little confusing is that the electron affinity is reported as a positive value even though that there's energy that's released when you gain an electron okay the next thing is that electron negativity right and so electron negativity electron negativity refers to the tendency of an atom of a given chemical element to attract shared electrons and so when I was really confused about this when I first learned about it basically if you think about it if uh you have a bond between I don't know Carbon and fluoride which atom is going to uh is going to bind is going to attract that electron in the shared Bond more U more readily it's going to be the fluoride because the fide has more protons that are closer to the valence electron that's in the bond than carbon does so fluide has the greatest electro negativity um and you can see that you know noble gases don't have an affinity for electrons and it would take energy to force an electron on them and here noble gases none of them have um electron negativity except for KR and XE okay I hope that all made sense if if you kind of just remember that the general trend is this way for most of these then you'll kind of just know what um these values mean now sometimes this is unchanged over here but it's it's mostly important to if you can just remember that most of the time fluoride is the highest you can kind of remember these terms okay the next thing to know is that um uh the common electr negativities you can figure out is H CNF if you remember that that hcnf because they commonly ask these terms you can figure out that they actually kind of EX Jump by 0. five every time so if you start at two and you end at four you can figure out what these common Electro negativities are remember Electro negativities is how uh how much force does an does the nucleus of an atom exert in a common bond in a in a calent bond right so if you have HF hydrochloric acid right the fluoride because its electro negativity is four and the hydrogen has only electr negativity of two you know that the um the fluoride is going to uh is going to share a little bit unevenly and have most of that the electron pair over hydrogen right they're going to share but they're going to share unevenly so that's important okay the only one that goes in the opposite direction of what we've been looking at is atomic size so francium is generally going to be the biggest because the there's the most number of protons sorry there there's um the electrons are furthest away right so that's kind of a bare minimum obviously hydrogen is going to be pretty small because the electrons are pretty close but Frum is at one of the highest energy states but the protons are are are holding it together a little bit less uh strong because there's only one proton in the for the outer shell right so you can kind of know that the atomic size goes in the other direction the final thing to know is that cations are generally smaller and anion are generally bigger the reason for that is anions is when you have extra electrons and catons is when you have extra protons or sorry when you have fewer electrons so yeah and so if you have fewer electrons there's going to be a greater tug if you have more an if you have more electrons then the electrons might repel each other a little bit but there's going to be less of a pull on them from the protons um if you have an i anion where the electron is added to a new energy level so a new shell then it's going to be pretty big because there's going to be fewer protons and the electron is being added to a greater energy State all right I hope that all makes sense um the next concept is bonding and chemical interactions all right hopefully you're still with me now we're going to go through General chemistry 3 which is bonding and chemical interactions this is not too bad even the Vesper stuff if you look at images it's going to be a lot easier the first thing is calent bonds calent bonds is when electrons are being shared between two elements um if and usually they're similar electro negativity uh if they're pretty high electro negativity then it could be an ionic bond if it's medium high electron negativity it could still be a calent bond but it could be a polar calent bond which is that one atom shares it unevenly with the other and might steal it a little bit more uh the example I gave before was hydrop Floric acid HF and that's a coent bond but that's a polar coent bond because if you remember hydrogen has a electron negativity two and FL fluoride has a common electro negativity of four okay um usually electro negativity it's polar if it's between 0.5 and 1.7 so I know I just said two but usually we say that it's ionic if um if it's like a metal and a non-metal rather than two non-metals but you can see that it it's usually between 0.5 and 1.7 is a polar bond and non-polar bonds is when the electrod negativity difference between the two atoms that are sharing the electrons is less than 0.5 so something like H2 it'll have electr negativity difference of zero and so that's going to be a non-polar Bond uh bond order this is pretty um self-explanatory but if you have uh a bond order of two that means you have two bonds a double bond and the more that bond order increases IE a double bond or triple bond it's going to have greater strength it's going to have greater energy and it's going to have less length so the atoms are going to be closer together so a triple bond actually holds the two atoms pretty close together um coordinate coent bonds always were confusing to me and that's when a single atom provides both bonding electrons um so it could happen in Lewis acidbase chemistry which we're going to go into later um but it's it's kind of this unique situation because usually we think of calent bonds is the two atoms sharing the electrons but in this case the one atom is providing both electrons to supply that bond between the two atoms is supplying both the electrons okay the next thing is ionic bonds and so here is a good um understanding of the bond type ionic is usually between a metal and non-metal calent is usually between two non-metals um but you can kind of figure it out based on the electro negativity difference too so if it's here then it's non-polar calent if it's here then it's polar coent and if it's here then it's ionic okay ionic bonds are formed from the transfer of one or more electrons from one element of a low ion uh of Low IE remember this is ionization energy and this low ionization energy means that when this electron is being released how much energy has to be added and so if there's if it doesn't have that much um ionization energy that means it's pretty easy to get rid of it to an element with relatively High electron affinity which means that how much energy is released when you add an electron and so usually this is when the electron negativity difference is greater than 1.7 cations refer to positive ions and anion refer to negative ions um so positive an positive ions are cations and this is when electrons have been removed and anion are when electrons have been added um it's important to know that cation doesn't mean protons have been added cations mean electrons have been removed crystalline lates are when you have large organized array of ions um okay inter molecular forces now this is pretty high yield you can have hydrogen intermolecular forces you can have dipole dipole pole you can have London dispersion and uh van their walls forces are is a term that includes both dial typle and London dispersion now it's important to know that calent and ionic bonds this always confused me for a long time is is within a molecule between atoms of the same molecule intermolecular forces is between two molecules right so let's say I have something like um say I have something like HF and uh H2O right so these are two different um molecules right and you can have this hydrogen bond between this hydrogen of the HF and the oxygen of the H2O and so that is a hydrogen Force an inter molecular force and you should know that it increases as you go up right so I want to give you an example of what London dispersion forces are dispersion force okay and let's look at it so London dispersion is kind of um it's kind of this interesting situation where you know you might have um like uh two helium right and helium is usually is a um it's what do you call it it's a it's noble gas right and so sometimes these electrons remember that they're not in fixed positions right and so you might create this this instantaneous dipole within it and so you can sometimes even though it's uh it's not a Charged particle or it's not polar you can have these redistribution of electrons that creates instantaneous dipoles and that might create a very weak um attraction or dispersion and so that's attraction or repulsion and that's called a London dispersion force now the next one is dipole dipole and dipole dipole are basically a little bit stronger and that's when you have um two polar molecules right remember polar is when it's between 0.5 and 1.7 and so the polar molecule can create attractions or repulsions and the attraction is going to be between the positive and negative components of one and the other the repulsions is going to be between positives or negatives right um so if you want to look at dipole dipole um example is hyrogen chloride hydrogen fluide and water right so you can see that the chloride is partially negative the hydrogen is partially positive the fluoride here and the hydrogen here now you should know that when hydrogen is one of those um one of those atoms that's involved in this dipole dipole Force there's a special name for that and that's called the hydrogen force and so hydrogen forces are really types of dipole dipole forces but since hydrogen is so small um you this is usually considered a special one because it's a little bit stronger than dipole dipole forces you should know that intermolecular forces are weaker than calent or ionic bonds right and and um things like London dispersion forces are pretty momentary and instantaneous okay Sigma bonds refer to the first bond between something um uh Pi bonds is the second or third Bond or the fourth Bond whatever right so a double bond is going to have one Sigma and one Pi a triple bond is going to have one Sigma and 2 pi so if I'm giving you an example I would tell you about uh c o right and so this has one Sigma Bond sorry this should be C and that has one Sigma Bond and one Pi Bond okay the next thing is formal charges formal charges are pretty difficult to understand um but let's say we take uh something like huh let's let's look at an example real quick formal charge example right okay so formal charge is kind of like when you're looking at something like this right and so we give the um when you have a bond you give one electron to this guy and when you have electrons you give each electron to that guy right so the formal charge is this carbon has a formal charge you can see that there's 1 2 3 4 five six right there's six bonds here so we give six and there's no lone pairs here so this has six and you know that normally carbon is supposed to have four because of where it is on the periodic table here remember carbon is right here and it has four electrons in its outer shell and so it has two more electrons here than it's normally supposed to have and so we'd say that the formal charge here is -2 okay let's do another example here we'd say that um basically um this is the formula formal charge is veence electrons minus dots minus sticks right and so here if we wanted to figure out what sulfur should have where is sulfur on it sulfur is right here it should have six electrons right so six and we see 1 2 3 4 5 six so there's six and so this formal charge is actually zero because it has what it's supposed to have let's look at this oxygen over here right this oxygen has one from this Bond and then one two 3 four five six so it seven and it's supposed to have if you look here it's supposed to have six right 1 two 3 4 five six and so this has a formal charge of negative 1 this also has a formal charge of negative 1 here and here have formal charge of zero and we said sulfur has a formal charge of zero so in total if I had to if I had to draw this it'd be uh Zer zero and zero and then negative one here and negative 1 here and if you add all these numbers and you got negative2 and that's why you see a negative -2 here okay I hope that was helpful uh just look at a couple more examples if that doesn't make sense okay the next thing is Vesper and I think Vesper is kind of something you have to memorize but it's not so difficult if you sort of look at a couple of shapes so that's what I searched up here and if you look at this you can see that uh you can see kind of what the uh what the examples are so a linear shape is kind of just a line trigonal planer is kind of like a triangle tetrahedral is kind of like a pyramid and then you get some weirder shapes like octahedral and trigonal pyramid B pyramidal but I guess just you should understand the concept first and then memorize it which is that when you have electrons that are surrounding an atom those electrons want to get as far away from each other as possible because remember they're all negatively charged and so they're going to create some sort of geometry and so this is kind of the definition of what geometry they're making um the hybridization refers to the um to the atomic orbitals that are being created by the bond right so let's say that I have um H2O right uh let's say let's use white okay uh let's say I have H2 so what is the shape of this right let's look at the shape of it H2O is probably a little difficult let's let's start with carbon dioxide carbon dioxide formula structure okay so I'm just going to show you this so carbon dioxide has a linear shape right these electrons on carbon want to get as far away from each other as possible there's no lone pairs here all the electrons are in Bonds on the carbon and so it's going to have a linear shape because we essentially have two spaces and so those spaces want to get as far away from each other as possible and so those are this is an SP structure okay let's say that um I have an SP2 or let's let's start with sp3 so what would be an sp3 let's say um NH H3 structure okay so this has an sp3 a trigonal pyramidal and you can see that this NH3 has one two three bonds and one lone pair and so this lone pair is going to take up a little bit more space and these bonds are also going to take up space so it's going to kind of be like a tetrahedral shape but since there's a lone pair it's going to be trigonal pyramidal right so uh it's going to be trigonal pyramidal right so you can kind of see there's three bonded Pairs and one lone pair so the geometry is going to be tetrahedral and it's going to be the shape is going to be trigonal pyramidal you can figure out what the bond angles here are by looking at what sort of hybridization does it have and so you can kind of just figure out how many electron groups are around the central atom how many of those are bonded pairs bonded pairs means how many bonds are there and how many lone pairs are there and then you can figure out what the shape is and then you can figure out what the angle is for that geometry okay um good uh I guess the last thing I want to mention is hybridization which is uh very confusing concept and let's just for me at least it was maybe it'll take you like a second to understand um but hybridization is kind of like let's see if I can get a good image hybridization kind of refers to the bonds that are um the bonds that are being formed between uh atoms right and so uh let's see okay so let's say here we can figure out what type of hybridization there is based on how many um how many attached atoms there are right or how many lone pairs there are and so you can figure out that Something Like Oxygen here has SP2 because it has one bond to the hydrogen one Bond over here and then it should have so you can figure out what the hybridization is by looking at how many things are surrounding it so here you see two lone Pairs and two attached atoms so that's sp3 because there's four you can look at two different groups that's four you can look at one lone pair one Bond and then two bonds here so there's three attached atoms and one lone pair so four these are all sp3 hybrid okay okay here here this is actually a pretty simple one which is compounds and sto geometry so the most important thing here is kind of uh mity and maybe equivalence sorry I'm using white marity and maybe equivalence right and so you just want to know basically marity is number of moles of whatever you're looking at over the over the liters of the solvent and the equivalence is kind of how many uh how many equivalents of H+ or H or yeah H+ or o minus are you forming here okay uh the naming ions is kind of important you want to know that if uh if you're looking at iron 2 then it's fairis and if you're looking at iron three then it's fair Rick this refers to the ion the cation right so if it's C+ then it's CIS and if it's cu2 plus then it's cpri so basically the the um the thing to remember is that it's us or I depending on the Lesser or greater charge right the other thing to know is that when you have an anion you remove the ending and you add an I so this is hydride fluide oxide sulfide nitride phosphide right the next thing is oxyanions oxyanion are polyatomic annion that contain oxygen so more oxygen is an eight and less oxygen is an night so the best example of this is nitrate and nitrite fewer oxygen that's nitrite more oxygens that's nitrate more oxygens that's sulfate fewer oxygen that sulfite the next one is um prefixes right so this is hypochlorite and this is chlorite and this is chlorate this is per chlorate right um so that's kind of a fun example too so there's only one oxygen here there's four oxygen so here hypochlorite chlorite chlorate and per chlorite the next one is how many hydrogens are bonded to it right so here you have H2 po4 minus which is diyd hydren phosphate here it's hydrogen sulfate a um a term that we use for this is B sufate right but this is hydrogen sulfate this is hydrogen carbonate but a term that a lot of chemists use is bicarbonate okay the next thing that you kind of have to remember is um uh so the I guess one thing you want to remember is then you're looking at an acid that I is when you have more oxygens and us is when you have fewer oxygen and us again is when you have fewer oxygens right so if I'm looking at HCL or sorry let's say say oxygen acids okay so if I'm looking at the acid version of of this right then it's an oxy acid and the annion name this one is hypochlorite but if I was looking at the acid version then it would be hypo CH chloris acid okay chloris acid chloric acid and perchloric acid makes sense okay the next thing to know is the type of reaction that we're looking at and so combination is when you combine two things decomposition is when you break down something combustion is when you add a hydrocarbon which means it's only made up of carbon and hydrogens with an oxygen and you get carbon dioxide and hyd and water okay and that's a pretty uh common uh equation that you can see whenever we're combusting something single displacement is when we um have a compound like uh like ag3 and we replace the AG with CU right so that's single displacement double displacement and when we just swap around the so calcium chloride and silver nitrate you kind of switch up the calcium and that silver okay the next thing is neutralization which is when you have an acid hydrochloric acid and base sodium hydroxide you add them and you get a salt NaCl and water H2O that's called a neutralization reaction you had an acid and base and you just result with a salt and a water okay now we're on chemical kinetics and and uh here it's pretty important that you know these equations in the order so we have zeroth order first order and second order and essentially what this means is that does the rate of the reaction depend on the substrate and if so how much does the substrate actually affect the rate and so in a zero order it doesn't affect it at all in a first order it does um affect it linearly and then second order the rate is affected by the square of the substrate and so um I always used have trouble memorizing these equations until what I actually did was start memorizing these graphs and then if you kind of remember these graphs because they're visual it's a lot easier to remember them and then you can derive these equations from those graphs so that's what I'll tell you over here so if you remember that this is a on the y axis and this is time and you remember that this is downward going and you remember that for all of these the slope is always K or negative K so the slope here is K which means that we know that the you know MX plus b we know that the MX is going to be negative KT where K negative K is the m and then T is the X plus b is B is where it's hits the Y AIS which is a knot um and that's going to equal the Y which is a and so that's how we get this equation so you can actually derive this equation if you just remember what this graph looks like now you can also derive the Half Lives of each of these by just remembering these graphs because you can think okay if I plug PL in where does a KN where does a equal half of a KN then you just get you subtract this on both sides you get ne 12 of AAL KT you get KTAL 1 12 a t and then you get the half life is equal to a not over 2K and I would recommend you just working that out by hand it'll make sense okay the next one is this one is a little bit more complicated first order so just remember that um the substrate affects this rate linearly and if you just remember this graph again you'll be able to derive this it's just a little bit more difficult so let's take we let's say we take um the Ln of both sides the natural log of both sides what we get if you remember logarithmic rules we get the Ln of this plus the Ln of this because that's how you do the natural log of two things multiplied is you're allowed to separate them if you add the natural logs of them so you get Ln of a equal Ln of a KN plus the Ln of e to^ of K T so the natural log of e^ KT is just KT which fortunately for us we get from the slope because this is the slope here is K plus the natural log of a KN which is actually where this um where this Y intercept is of this line it's the natural log of a KN and that's equal to the natural log of a so I'd recommend you just take the natural log of this equation and try to derive it by hand and it'll make sense to you how you can take take that from this graph then third graph is a second order reaction unfortunately this is a little bit easier so in this equation you can see this thing we know the slope is positive K so it's positive KT plus the Y intercept here would be 1/ a KN so 1/ a plus KT = 1 / a which is our y so that's kind of how you can derive this so again what you really have to memorize is that this graph points downward this graph points downward this graph points upward so you can figure out if it's negative K or positive k and then the second thing you would have to memorize is these uh Y what do these y's represent if you can remember that then you can derive basically you can derive all of this um which is pretty amazing if you just remember like this goes down this goes down this goes up and you remember that this is 1 / a this is natural log of a this is a um and then finally you have the rate units of rate constant um this should make sense to you if you just kind of plug it in for K so the rate is moles over seconds which makes sense and then for here you have rate equals K * um something so this already has the unit molar right so you know that the rate has to be mol molar over second so you just do K is 1 over second so now you get molar over second and then finally you know here that this is molar squared so if you do one over M second then you get mol over second so again you can just try that by hand and it'll make sense why these units are true so again if you just remember this you can derive everything over here and it's a lot simpler okay the next thing to mention is that these over here this is a lot closer to like a straight line so it's a lot closer to a first order kinetics equation and then over here this is a lot closer to a zero order kinetics reaction because as you add more substrate it doesn't really change the rate over here as you add more substrate over here it's almost kind of like a straight line where it's going upward um so that's that's what this is saying over here and remember this is called the michis menus curve this is kind of how those two scientists describe the rate of enzymes reacting with substrates okay next you have types of reactions so over here um this is pretty high yield too so combination is when you combine two things decomposition is when a single thing breaks down combustion is when you add hydrocarbon and oxygen and you get carbon dioxide and water single displacement is when you take like a atom and you add it to a compound and then your your Ion switch places and then you have double displacement which is kind of the same thing as single displacement but it's happening with both compounds so you're switching them around so you get this calcium is now bonded to this nitrate and this um silver is now bonded to this chloride now you have neutralization neutralization is a type of double replacement reaction so this is um when you take an acid and a base and you make a salt in water so HCL plus sodium hydroxide makes sodium chloride plus uh water and then you have hydrolysis and hydrolysis when you take water and you break down a bond um okay next we have Gibbs free energy so Gibbs free energy is kind of telling you does the universe want this reaction to happen or not if Gibs free energy is negative then it's exonic the universe wants it to happen and if it's positive then it's endergonic the universe doesn't naturally uh spontaneously move in that direction you calculate gives free energy based on the heat that the reaction makes and you um also calculate it based on the the entropy that the reaction makes and so uh if the entropy if it increases if the reaction increases entropy and also releases heat then the universe wants that to happen and that's kind of how um gives free energy is calculated you should know the equation for gives free energy but we'll get to that later okay next is the arenus equation so arenus equation is k equal a * e to the^ of EA over RT this is a very important equation and uh here we also get definition of rate so if you have these four compounds that are uh that are reacting then the rate is equal to how fast do we get rid of this um compound it's also equal to how fast do we get rid of this compound it's also equal to how fast do we make this compound it's also equal to how fast we make this compound now you have to take into the fact that there's these coefficients as well so you have to divide it by the coefficients because let's say here it's 5 C + 1D then we're supposed to make five times more of C as compared to D and so that's why we divide by these coefficients now we have the rate law and the rate law you just take the substrates so this a and the B and you multi you um do it to the power of some value X and Y and you multiply it by a rate constant and that's how you get the rate of the reaction um and it's also important to know that these are not just the coefficients of the reaction these are things that you can only find by the actually doing the experiment and figuring out like oh how fast um how how much do a and b manipulate the equation so sometimes in the MCAT they'll actually give you lab values and they'll tell you like oh um uh when a goes from 1 to four this reaction doubled and so now you should be able to say like oh what is the exponent for a and when B went from 1 to two this reaction aex so now you should be able to tell me like what's the coic what's the exponent for B now we have radioactive decay and I went through this in the physic section as well but um radioactive decay is just telling you how fast does um some of the radioactive elements decompose and so this is the equation that describes that also very high yield you should know this equation okay next we have reaction mechanism so you have um um you have multiple steps in a reaction even though it just the reaction might just be one thing there's actually multiple steps that are going on in that reaction and one of those steps is a rate determining step that's the slowest step and basically everything else is dependent on how fast or how slow does that rate limiting step go uh we call the middle compounds intermediates because those don't actually show up in our final equation those are things that you know we produce in the middle in step one and then in step two we get rid of it and so that's why those are called intermediates but it is really really high yield to know what a rate determining step is is it's just the slowest step okay now we have arenus equation also very high yield it's more high yield to know the relationships here than to actually know the equation itself um so I talked about arenus equation um this is the rate over here the rate constant and this is basically how do we determine what the rate constant of an equation is so it's equal to this thing called The Frequency factor which is going to be given to you times e to the power of netive EA that's the activation energy in the reaction divided by the gas constant times the temperature in Kelvin so it's also important to know that this T over here is represented in kelvin and you want to make the conversion um before you do anything so remember add 273 to the Celsius okay um it's important to know the trends here so as you increase the frequency factor a you're going to get a higher rate constant as you increase the T well we have to reason this out so T goes up which means that this thing let's forget about the negative sign for now that means this fraction if T goes up this fraction is going down but now we have to factor in the negative sign so now we know that this fraction is going up right now e to the power of a fraction that's increased is increased and so that's why the K is higher work this out by hand because it'll make a lot more sense but that means that when T is increasing so is K and so that kind of logically makes sense too if you have like all these atoms that need to react with each other if it's really cold and there's not much temp if the temperature is really small these uh compounds are not going to move that quickly and bump into each other but when the temperature is really really high these compounds are all going to hit each other and so we're going to have a higher rate constant so that's what that's saying okay now we have equilibrium constant so this is um the same equation that we were looking at before we can represent the equil equilibrium constant by just taking c and d and and uh adding coefficients to it um by exponents and then we divide it by A and B and again we take the coefficients and make those exponents and that's called the equilibrium constant by figuring out uh what this is what this um value is basically what you're doing is you're taking the the molar of the substrates here of these compounds so let's say I told you oh I have five molar of this and I have like two molar of this and I have one mol of this and I have three molers of this that's going to tell you like the KQ what is the what is the equilibrium constant here now we also have the reaction quotient which is QC and over here it's important to know that QC is actually like how much of everything do you actually have so if I have five 4 1 2 right those are the values I put into QC case KQ is like um telling you what is the normal equilibrium constant for that reaction and I recommend you just do like a question from neworld or some free online resource about uh reaction quotients and equilibrium constants because it'll make a lot more sense when you actually do a question and you'll understand like oh if the if the like what I'll get into here it'll basically tell you which direction does the reaction go so when I talk about this equation over here I want to figure out like is this equation more likely to go this way or is it more likely to go this way because this equation can go in either direction and it actually depends on how much of these um of these compounds do I have and so when you have a lot of a it's more likely to push this equation this way and when I have a lot of D it's more likely to push this equation this way and so that is what informs the QC value and so if my QC is smaller than the KQ then this reaction again is going to go this way if my K if my KQ is equal to q that means that this reaction is in equilibrium it means that Delta G that gives free energy is zero and so the equation is not going to go one way or the other it's just going to stay there and then if Q is greater than k Q then that means there's a lot more of this than there is of this and so the equation is going to go this way so again just do a a practice example of this and it'll make more sense usually how it'll show up is they tell you what is the what is the amount of each of these uh do you actually have and then it'll tell you oh the normal KQ of this um of this re this reaction is like five and you have to calculate the QC and the QC will be like one or something and you know one is less than five so you know the equation based on this is going to go this way all right now we have kinetic and thermodynamic control so kinetic products versus thermodynamic uh products I'm going to show you an example because it'll be easier okay so this is um this is the difference between so this is a thermodynamic product over here because the activation energy is a lot higher so it takes a lot more energy to to go over and actually make this end product e but this e end product is a lot more stable than D over here so this is a thermodynamic product it's it's um the Gibs free energy is a lot greater it just takes a lot more energy to actually get there now kinetic product is just what you would get to without um as much activation energy and so you don't get as much of a stable product at the end but it's a lot easier meaning it takes a lot less activation energy to get there so that's the difference okay so that's kinetic higher and free energy these are the products that and form can form at lower uh temperatures they're fast in quotes because they can form more quickly under such conditions these thermodynamic products are slower but more spontaneous meaning more negative Delta G and that's important it's more spontaneous the universe wants to make that more okay um L shot's principle if stress is applied to a system the system shifts to relieve that stress remember when I was saying like if you have a lot of the of the products then you'll shift toward the substrate and you have a lot of substrate you'll shift toward the product that's basically the shot principle now this is a good um question that they might use to apply multiple different principles which is let's say um this is happening in the body this is a reaction this is actually something that's going to come up in med school a lot which is okay this person has this bicarbonate buffer in their system let's say now we um give them a medicine that's going to increase the pH in their gut or something right so what's going to happen is if we increase the pH that means we're decreasing the h plus which means it's going to go this sorry it's going to go because we're decreasing the H+ we want to make more of it so that's why um the equation is going to go towards the right and so that means essentially that we're going to have less respiration because we're going more this way so that's why this is less respiration because we have less respiration we're not going to breathe as much and we're going to have more trap CO2 now over here it's less pH which means higher H+ and that means that we're going to go this way which means we're going to produce more carbon dioxide which means we're going to respirate more and blow off that CO2 so that's basically the shers principle okay next we have systems and processes and this is thermochemistry so systems and processes we have isolated system closed system open system isothermal adiabatic I used to always be confused with these until uh I kind of simplified it for myself so let's say this is a system right if it's isolated that means nothing is getting in or out and there's no heat exchange and there's no energy uh there's no matter exchange if it's a closed system that's more like a normal system where there can be heat Escape or heat entering but there's no matter that's leaving like um nothing no physical elements are leaving then we have an open system and open systems is like I think of it like an open fence like matter can leave and so it can energy so anything can come in or out that's open system now isothermal processes is when you have a constant temperature so um let's say like there's this gas with a piston in it right uh let's say the gas is expanding right usually when the gas is expanding it's uh gas is expanding it's doing work and so there might be heat that's leaving right but you might have like temperature that's uh constantly uh heating this up and so that's a isothermal process because there's constant temperature in here even though there's heat exchange happening adiabatic means there's no heat exchange happening but the temperature of this might change there's just no heat exchange so this might be getting cooler as it's doing work and releasing heat but sorry sorry let me repeat myself so adiabatic means there's no heat exchange with the environment so um you can imagine like uh this is so uh thick walls that there's no heat exchange and so this is the same um Heat at the same time the temperature might be changing but the heat is the same now we have isobaric and isov volumetric isobaric means there's constant pressure isov volumetric means constant volume now um let's talk about State and State functions so State functions represents the equilibrium State these are pathway independent so this is like pressure density temperature volume enthalpy internal energy gives free energy entropy these are just physical properties of our equilibrium right it's not going to uh it's not going to change any like the the path is not going to change anything about our equilibrium values this gives free energy of reaction is going to stay the same uh whether or not we have different um amounts of the substrate or the product the internal energy is not going to change the pressure is not going to change those are things okay standard conditions is kind of important because um they might they might give you reactions happening in standard conditions so just remember this is 298 one at atmosphere then one molar those are standard conditions for gases okay then we have Fusion freezing vaporization sublimation deposition so Fusion is a solid going to liquid freezing is liquid to solid vaporization is liquid to gas sublimation is solid to gas and then deposition is gas to solid just remember all of these These are important and then triple point is this unique point where all three of those uh states can coexist so you you can uh have at that point of temperature and pressure you can have a solid liquid or gas you can also have a supercritical fluid which is kind of like in this space where the density of the gas is equal to the density of liquid and there's no distinction between those two phases all right now we have Gibs free energy and this is what I was talking about before so we have um the enthalpy and the entropy and those are what determines gives free energy so just remember that this is the equation and they might give you these values and you'll have to figure out oh is is Gibs free energy negative or positive and it's it's important to know that reactions that have negative Gibs free energy are spontaneous this is kind of a chart to help you out with this equation okay next we have temperature and heat so temperature is the measure of the average kinetic energy of a substance so you can imagine like this is a box and these are all the particles and if they're moving around really quickly that means that there's a high temperature if they're moving around really slowly then that's a low temperature and that's kind of how you can measure um what temperature is this is just um helpful points to remember so I try to remember body temperature is 37 degrees or 98.6 um and I also remember 0 degrees or 32 degre is freezing this is the equation not too high yield that you know this equation okay heat is just the transfer of energy that results from differences in temperature so if you have a hot cup of coffee on a cold day then that there's going to be heat exchange because this is has a higher temperature than the surroundings okay now we have enthalpy so enthalpy is the measure of potential energy of a system found in intermolecular attractions and chemical bonds um you can imagine that if there's a lot of um chemical bonds that are causing higher enthalpy then maybe um that might result in like if if this is a very unstable bond between these two things then there might be a desire to break that Bond and release a lot of energy phase changes um so solid to liquid to gas that's endothermic that requires heat right uh if you have an ice cube it's only going to melt if there's a hot sun outside so that's what that's saying basically and then gas to liquid to solid is exothermic it releases heat so when a gas goes into liquid and then a liquid goes into solid that's releasing heat hess's law is that enthalpy changes are additive and you're probably going to be tested on this I would do just a question on test on hess's Law and it's going to make a lot more sense but basically you just take um the the uh the reaction the heat of formation for that reaction action and that's going to equal the heat that it took to make those products minus the heat that the reactants uh you can also do this using Bond dis Association energies and so this in this one it's reverse and that's because you're actually disassociating um the reactants rather than the products and so that's why you do the reverse over here because um yeah that's basically how it works so heat of formation and Heat and the bond disassociation these are kind of like opposites right so that's why you flip the equations around now you have entropy entropy is just the disorderness of that system and it's equal to Q / T just remember this this is an important equation and uh just know that the standard entropy of reaction is the the entropy change that it took to make the products minus the entropy change that it took to make the reactants okay um now we have Gibbs free energy and this is the same equation I talked about before again it's just the products minus the reactants and uh we can figure it out actually from just the KQ the equilibrium constant the equilibrium constant is just what are the concentrations at equilibrium of the substrates in the products and so you do this equation and you can figure out what is the free energy that's produced by this reaction you can also do it by figuring out the Q and basically that's going to tell you what is the free energy currently and if the free energy at this point is less than zero then that means that it's a spontaneous it was spontaneous to reach that point but if it's greater greater than zero then it's non-spontaneous and the difference between Delta G and Delta G Prime always confus me so this is the free energy at equilibrium this is the free energy at the point that you are at so it's kind of like the difference between q and k k is a representation of equilibrium Q is just where you are based on the uh substrates and products that you have okay okay next we're on uh gas phas and here um this is pretty high yield so um we have ideal gases and STP STP is uh the standard condition so uh if somebody says that you are at STP that means you're at 0° CS 273° Kelvin and 1 atm and at STP one mole of gas is 22.4 L that's also pretty important for you to know uh I'd say the most important thing here is the 1 atm is 760 mmhg that'll save you a lot of time and then it's also kind of helpful to know it's about 100 kilopascals or kPa um so that's pretty helpful too t and mmhg is the same thing or same like unit conversion ideal gases are just theoretical gases when you have like this box and the this gas the molecules are bouncing around usually these molecules actually take up space and when they hit each other there's some energy that's lost um but in ideal gases you just consider that these particles are just super tiny and that there's no uh energy that's loss these collisions are perfectly elastic um this happens usually when the temperature is really high so these particles are moving around really quickly and the pressure is very low um next we have the ideal gas law this is super high yield make sure you know this like the back of your hand PV equals nrt R is 8.314 Jew per M mole K uh and then the density of gas is just the the uh PM over RT that's also very high yield to know um so if somebody gives you the marity and the pressure and the volume uh you can know the and the sorry and the temperature some you should be able to figure out the density of that gas um this is the combined gas law this is kind of the one that combines all three of these laws and this law is that PV overt equals PV overt um and basically what you're doing is you're taking this equation and um you just know that n is constant and so you're able to derive this combined gas law Bo Charles and G Lu they are people who figured out like the relationship between p v and T and once they figured that out they kind of you can combine those laws into the combined gas law uh okay um the last thing that um the combined gas law does not include is the avadas principle which kind of takes the N part into it so um if you have N1 over V1 that's equal to N2 over V2 so these are again very important laws to know you can figure out a lot about the pressure of a gas the temperature of a gas the volume of gas um the number of moles in the gas just based on these equations okay um so now we have Dalton's law and Dalton's law is just that the total pressure so if I have this um box and there's like gas a and gas B and gas C I can just add these the pressure of these gases and I'll get the total pressure in that box um there's also Dalton's law which is that if I if I give you the total pressure and then I tell you like oh the mole fraction of gas a is like one out of five then you can figure out the um you the gas a is just 1/ of the total part of the total pressure of the gases Henry's law is this thing um the M marity of a is dependent on the pressure of a times this constant and so that's kind of Henry's law uh again all of these are pretty important to know you'll probably get questions on this but it's really easy to get this down if you just do one or two questions on gas laws and you'll you'll be able to solve all the questions that you get next is datomic gases so this is probably going to show up too um just know that the hn f i CB this is a really helpful pneumonic I used to use this pneumonic all the time to remember all the ones that have um that exist as diatomic particles so you're not going to see uh just um that you're going to see always like it's going to be like this or you're not going to see like o alone you're going to see O2 so these are all usually exist as Dion iic molecules okay the next is real gases remember when I said ideal gases usually are under high temperature low pressure well real gases deviate from ideal Behavior those particles actually do take up space and they do um lose energy when they hit each other and that happens usually when there's low temperature and high pressure um okay so now this is a little bit less high yield and a little bit more complicated I'll talk about Vander walls equation first again it's not that important that you know it but this minus NB basically accounts for the fact that these particles have volume and so that's why we're subtracting from the volume of the gas and then this accounts for the fact that there's attractive forces between these particles and so when these particles are bouncing around and hitting each other there's some attractive forces and so there's a little bit more pressure than you would have in an ideal gas and that's what this is just basically a modified equation for PV equals nrt okay now you have this this is again not that high yield for you to know if you have moderately elevated pressure lower temperature then the real gases are going to occupy less volume the reason for that is because these particles have inter molecular attraction and so they're going to be attracted to each other and so this gas will take up less space than if it was an ideal gas but at extremely low temperature and high pressure what's going to happen is that these real gases will take up more volume because the particles themselves are actually taking up space they're actually a lot bigger than in an ideal gas where you just assume that these particles take up negligable space so that's um that's again not that important that you remember but it's helpful to understand why that's true okay now we have kinetic Mo molecular theory and we've kind of already gone over this but um if you have this gas and these particles are all moving around you can figure out what is the kinetic energy of a gas based on 12 mv^ 2 and you can also uh realize that based on this equation you will realize that the kinetic energy of a gas is directly related to the temperature of that gas so at higher temperatures that means that kinetic energy is higher which means that this velocity is higher so these particles are moving faster at greater um molar masses then the molecules are moving slower and that makes sense they're heavier so they're going to be slower than if they were uh lighter okay this is also important this is root mean squared I want you to remember this equation basically it's square root of 3 RT over um mol over marity and um the important thing is that you just understand this relationship so here we know that the speed is kind of directly related to the temperature which we just talked about and inversely related to the marity which is kind of similar to the heaviness of that particle um diffusion is that the spreading out of particles so you can imagine if you have like really dense particles after you spray a freeze bottle it's going to diffuse through the air to all the places that are less full of that particle and a fusion is the movement of gas from um one opening to another opening so this is like an example of effusion so effusion is these gases that are in this box are just going across to the side that's a fusion um and it's usually through a smaller opening so it has to be through a smaller opening that's a fusion okay now we have grams law grams law is basically that R1 over R2 is inversely proportional to the root of M2 over M1 um so basically what that's saying is that the greater the marar mass the slower the diffusion or diffusion that again makes sense if this gas is just heavier then it's going to go slower but if this gas is lighter then it's going to go quicker um the diffusion and diffusion is going to be faster so that's that's what grams law is again it's really important that you understand these equations but it's more important that you understand the relationship between the variables than the actual equations themselves the equations are important they might ask you like what is the value but they're more likely to ask you um based on these two molarities what's the relationship between these two gases okay these are the seven diatomic gases now we're on Solutions so Solutions the terminology solution is a homogeneous mixture so there's um basically this mixture and there's solvent particles and solvent particles is kind of like like water is a really popular solvent and those surround solute particles and they're um surrounded by electrostatic interactions so you can imagine like a solution of NAC and water and the water the H2 molecules have electrostatic interactions because of this dipole that hydrogen and oxygen form and those have electrostatic interactions with the NAC now we have solvation or dissolution and that's basically when um this solute dissolves in the solvent so you can imagine salt dissolving in water and what's happening is that the na+ is splitting up with the CL um minus into ions um and it's important to know um that most solution are endothermic but the dissolution of gas into liquid is exothermic it's probably not going to show up too much but it's just kind of important to understand why that's true now we have solubility solubility is just the maximum amount of solute that you can dissolve in a solvent in a given temperature you can imagine that if you have a cup of water you can add salt to it and it's going to dissolve but there can be like so you can add like such an excessive amount of salt that eventually um you won't be able to dissolve that salt anymore uh and that's what solubility is referring to molar solubility just the marity of solute at saturation saturation is the is basically like you keep adding salt until um you can't add any more salt because otherwise it's going to precipitate you have complex ions complex ions is a cation bonded to at least one liend in which there's electron pair donor and um I'll show you an example of complex ions so this is an example of a complex ion over here you can see that there's a copper and then there's all these uh H2O particles that are um lians of this copper particle and those are basically that's a complex ion so solubility in water is something I just talked about now we're on concentration concentration is U you can imagine percent by mass so this is all really important just definitions that you should know um so the mass solute over the mass solution times 100% that's the percent by mass concentration um we have the mole fraction mole fraction is just the moles of the solu over the total number of moles we have marity marity is moles of solute over liters of solution so if I told you there's one mole of um NAC in one liter of water that's one molar and then there's mity that's moles of solvent moles of solute over kilograms of solvent so um it's I guess one thing that I should have uh mentioned here is that I mistakenly said one liter of water I should have said one liter of solution because this denominator is referring to the solution which is both of those combined the NaCl and the water this is kilog of solvent which is just the kilograms of the water so that should make sense and then we have normality normality is the number of equivalents divided by the lers of solution um so um a good example I was always confused about normality but you can imagine H3 P4 so there's multiple equivalents here because the number of H+ uh units that are being formed is actually three times and so that's what that's referring to number of equivalents um okay now we have dilutions U and so this is a really important uh concept and you're definitely going to be asked about this and it's a pretty simple equation but it's kind of hard to understand when to apply it so basically if I told you like um I have one mole of um NAC solution or sorry one mole of Na in one liter of solution basically that means that there's one molar right in one liter solution now let's say I want to dilute this so that it's actually 0.5 molar how many uh how much water do I need to make this one molar solution into 0.5 molar well that's when I just use this equation so I know that this value is one I know this value is also one I know this value is 0.5 so what is the volume of solution I need and then you can just figure out oh okay this is actually two so I need to get an extra liter of solution to make this um more dilute okay now we have Solutions equilibrium so this is solubility product constant so this is KSP KSP is basically kind of like the same concept as KQ this is telling us more about like what is the equilibrium constant for this dissolution equation and so um you're going to have an ion product ion product is basically the same thing as q and KSP is the same thing as k um and you'll see that if IP IP is Ion product is something that describes where is the solution right now and KSP is describing where is the solution at equilibrium and so if IP is less than KSP that means that this solution can actually handle more solute if IP is equal to KSP that means that the solution is saturated and if IP is greater than KSP that means that there's going to be a precipitation precipitate is like um there's solid coming out of the solution because it can't handle any more of the solute um so you might see like uh sodium chloride crystal in a solution of super saturated uh water uh NAC solution just because this is super saturated and so that's what these are telling you um okay now we have formation or stability constant this is just KF and that's basically the equilibrium constant for complex formation usually it's much greater than KSP we have the common ion effect and common ion effect is just describing that um there's lower solubility of a compound in solution when it already contains one of those Solutions in the compound so this an example of this would be like let's say this is my solution and I have like a calcium chloride that's already been dissolved so there's already a lot of chloride ions in this solution right um and now I'm trying to dissolve NAC in this uh solution well because I'm trying to dissolve NAC in the solution it already has a lot of chloride ions so there's going to be the common ion effect and so there's going to be a lot less sodium chloride that's able to dissolve just because there's already a lot of chloride in that solution now we have colan and cation is something that they use in industrial chemistry where they'll try to sequester toxic metals from Water by just adding a central uh cation like what I was showing you before like let's say they add copper and now all these um all these things will be ligans to that copper um or they'll use like um these ligans and they'll try to precipitate out the this toxic metal okay now we're on solubility rules these I would just try to memorize and I think um if you haven't memorized them from chemistry class already I think the best way to memorize it is just kind of look at the periodic table and be able to memorize it from there so sodium pottassium ammonia these are always soluble um this nitrate is always soluble chloride bromide iodide is always soluble except when they're with these three compounds um this is soluble except when there it's with this so just kind of look at the periodic table and be able to say like okay this is soluble this is soluble this is soluble except when it's with this and I'll let you try to memorize these uh this is just again really high yield and I'm sure you were tested on this in chemistry class as well so just try to try your best to memorize all of this okay now we have colligative proc properties um so this is kind of a little bit more about boiling point elevation freezing point depression osmolarity osmotic pressure so colligative properties is just the physical properties of solution and it depends on the dissolved particles um and so the important thing is that it doesn't really matter about the the chemical identity which dissolved particle it is like is it a lot of pro um protons is it a lot of like chloride ions it doesn't matter about that more it matters about the concentration of those dissolved particles um so you have vapor pressure depression you have boiling point elevation and then you have freezing point depression so basically what these are referring to is that if I have a cup of water the freezing point is zero um boiling point is 100 right for Celsius but then if I um add some particles to it now the freezing point might be like -3 and the boiling point might be like one 104 and these two equations you can read them those are the equations that describe like what is the new what is the change in the freezing point and what is the change in the boiling point and that's the way that you can figure out so I try to always remember that solutes are going to um increase the range of my um freezing and boiling points it's going to make the boiling point higher and it's going to make the freezing point lower then we have rals law and that's vapor pressure depression and so that's basically saying um the presence of other solutes will decrease the evaporation rate of the solvent and so that means means that there's a decrease in the pressure for vaporization so that's also an important thing to know all right now we have osmolarity osmolarity is just the number of individual particles in the solution so because NAC dissolves completely one molar of NAC is two Osmos per liter because you know the NAC splits up into Na and Cl and so that's one aom and that's another aom okay now we have osmotic pressure and this is the sucking pressure that's generated by Solutions in which water is drawn into the solution um and this is not like a super high yield thing for you to memorize but it is important to you for you to know the the relationship so this is osmotic pressure this is the molarity and then this is the temperature and this is gas constant and this is just a constant vent h factor so that's the osmotic pressure that's the suing pressure um generated by Solutions in which water is drawn into the solution something we learned in med school is that um there's this thing called osmotic diarrhea which is that there's this um there's this basically it's watery diarrhea caused by this osmotic pressure okay now let's talk about acids and bases so we have arenus acid arenus base bronzed Lowry acid bronzed Lowry base so arenus acid basically makes H+ this is the original definition of of acids and then arenus bases produce o minus then they decided that they need to expand the definition a little bit and so they said bronstad lowy acids they donate H+ versus bronstad lowy bases accept H+ and then finally we had leis acids and LS bases and that's just basically about electrons LS acids accept electrons Lewis bases donate electrons and so it's kind of the opposite donation and accepting uh relationship here um but this is what L LS acid and LS bases describe these are all technically definitions of acids and bases it just depends on how you define an acid or a base okay um and then it's also important to know that this sorry like arenus base might describe a compound that's not necessarily A Lewis base and a bronze to Lowry base might be different from a Lewis base so these compounds might not be the exact same they're similar but sometimes there's exceptions to um their overlap okay now there's aiic species so that means that um something can be both an acid or a base and then we have polyic acids which means that there's multiple H atoms so like H3 P4 you have multiple um uh protons that can leave this and so that's a polyprotic acid okay now we have the water disassociation constant really memorize this 10 the4 that's very important and then remember that k a * KB is 104 is KW all right pH P you have to know this um or you should know this by your ex exam that pH is negative log H+ p is negative log o minus and then pH plus p is equal to 14 make sure you remember this is a really high yield H+ is 10 to the Negative PH 10 to the power of Negative PH okay um this is kind of helpful P P value you can approximate as um as the negative B over here plus uh 0. a and if you do um you know 10 to the power you'll kind of understand the reasoning behind that um um okay there's strong acids and strong bases and then weak acids and weak bases it's very important to know the difference here strong acid if I put it in water like H2 so4 right if I put this in water it's immediately going to disassociate into the H+ plus the HS so4 minus uh versus like a weaker or like HCL right um HCL is immediately going to disassociate you won't see any of HCL in water it'll always disassociate immediately weak acids and weak bases don't completely disassociate so there's still some of that compound left over there's acid disassociation and base disassociation constant um and this basically is you take the h3o plus Con in the con in the solution you take the a minus in the solution you multiply them and then divide it by ha that's Ka and you can do something similar for KB and then you can figure out PKA and pkb and that's basically telling you how strong is the acid or how strong is the base these are all measures of how strong is your acid or base based on how much disassociation happens so you can imagine if there's like if there's so much disassociation then this numerator will be high and this will be a strong acid if there's so much disassociation here there's going to be a very strong base and then PKA plus PK b equals pkw which is equal to 14 this is like basically the same equation as this right here okay now we have conjugate acids conjugate bases so if you have a strong acid you have a weak conjugate that should make sense because basically for you to go from h c um that that produces H+ plus CL minus now for H+ and cl minus to to form HCL that's like for cl minus to to pair up with an H+ and form HCL that's like basically impossible so that's why it's a very weak conjugate we wouldn't even call it a base at that point um so that's that's that and then we have neutralization reactions neutralization reactions form salt and then sometimes H2O okay uh now we have buffers buffers are very important physiologically it's basically we take a weak acid or a weak base and it's conjugate salt and it resists the changes in PH so it's really important in your body to have buffers um like the hc3 system this is a weak um this is a weak um acid right and so it helps to buffer and resist changes in PH um okay now we have Henderson sorry hco3 is a weak base I should mention because it um you can form H2 CO3 and this is kind of the equation um that happens okay now we have Henderson hosle equation make sure you memorize this is a very important pH equal PKA plus log base over acid and then this is kind of the opposite P equal pkb plus log um log base over acid and uh this is again really really high yield for you to remember um because basically you can figure out what is the relationship between pH and PKA based on these this um this ratio okay [Music] um uh okay and then the other thing to mention this is kind of helpful is that when the uh base over acid is equal so it's at the half equivalence point then this becomes one which means log of one is zero which means that the pH is equal to the pka so if you're looking at a titration curve and I'm skipping a little bit but if you look at the point at which there's half equivalence point you can actually figure out what is the pH of that solution so if I'm working with like um some base or acid that I'm not so this is a base actually so if I'm not actually sure what is this base I can figure out what the pH of this is by just looking at the half equivalence point and that's over here and then I can figure out oh well the pH is about 10 n over here so that means that the pka is 9 and I can actually figure out like what what base is this based on that um okay now we have um polyvalence and normality so we've kind of already gone over that equivalence is one mole of the species of Interest normality is the number of equivalents in a solution and so if I took H3 po4 there's six um there's six equivalents or six uh normality of this because there's one mole of this creates three moles of H+ so two Mo mol of this is six normality okay now we have polyvalent polyvalent means it accepts multiple equivalence or donates multiple equivalence so this is a polyvalent acid like we talked before all right now we have titration so titrations is something you've talked about in chemistry lab already you have half equivalence point which is what I just mentioned you also have equivalence point equivalence point is the point at which there's equal amounts of acid and base so this is the equivalence point over here it's a very important point for you to know and it's basically halfway through the downward uh trajectory of that um okay now we have pH at equivalence point so pH at equivalence point if it's a strong acid that you're titrating with a strong base then pH is going to be seven and then the others you can kind of Reason through if it's a weak acid that you're titrating with a strong base well then pH is going to be greater than seven if it's a weak base strong acid pH will be less than seven so you can kind of Reason through that indicators help you figure out well where should the um indicators are basically things that change color close to a place where um you expect the pH to change and so if if the color suddenly changes at like SE ph7 then I know like oh we're at ph7 and it just helps us kind of look at the titration itself these are tests that you can use not too important that you remember all of these but like the litmus test acid or red base is blue neutral is purple again not too important that you know this endpoint is when the indicator reaches full color so basically endpoint is going to be if we chose our indicator properly endpoint should be somewhere close to the equivalence point okay and then we have polyvalent acid base titrations and so there's in polyvalent acid based titrations there's going to be multiple uh points at which you can find uh equivalence points okay so this is basically what a titration looks like and I'm not going to go too much into it because this is probably something that you've looked at in chemistry lab before okay almost done we're on oxidation and reduction reactions now so oxidation is loss of electrons reduction is gain of reductions of electrons I'm I'm sure you've heard of uh of I'm forgetting the pneumonic for it so this is the pneumonic that I was forgetting oil rig uh oxidation is loss reduction is gain that's kind of helpful for me um okay so with respect to oxygen transfer oxy oxidation is it's very helpful to know that oxidation is gain of oxygen which kind of makes sense and then reduction is loss of oxygen an oxidizing agent and a reducing agent it's really confusing how these work but basically an oxidizing agent helps other things get oxidized so oxidizing agents gets reduced and reducing agents gets oxidized now we have oxidation rules and oxidation rules is any um is basically how do you determine what the oxidation of something is in a compound so if I have like H2 um P4 minus right the oxidation rule will help you figure out what is the oxidation number for each of those like H would be + one then P you can figure out oxygen is going to be minus two and so you just kind of have to walk through these and understand like okay this is free elements so if I just have like um I don't know na then that's just going to be zero if I have na+ like um the cation that's just going to be plus one group one a metals are going to be plus one when they're in compounds group 2 a metals are going to be plus two um group 7A in compounds are going to be minus one unless they're combined with an element of Greater electr negativity and then H is going to be usually plus one unless it's like um paired with a less electronegative element then it's minus1 O is going to be min-2 unless it's like H2O2 in which case it's going to be minus1 and then the sum of the oxidation numbers this is really important must equal the overall charge that's what's going to help you the most okay um now we're on net ionic equations or let me go through balancing half actually let's do net ionic equations so net ionic equations is basically let's say I had like um uh some spectator ions so na plus um let let me show you an example so this is an example of how we find like the complete ionic equation and then the net equation so you see all these aquous things right that are reacting and out of those aquous things we actually get a solid but then we get these other aquous ions and so these aquous ions actually cancel out because there's no change they're still aquous we haven't changed anything and so basically this is going to be our net ionic equation that's how you can think of that um so that's net ionic equations you ignore spectator ions spectator ions don't do anything there's complete ionic equations which shows all the ions uh you have disproportionation reactions not too important that you know this but it's a type of Redux reaction in which an element both is oxidized and reduced so you can calculate the oxidation States and you can see like oh this oxygen both got uh oxidized and got reduced so you can see like in examples where oxygen um is like a zero and then it becomes a minus1 and aus2 or sorry let's say there's H2O2 and then somehow it forms just normal oxygen which is a zero and then it forms like H2O which is a minus two right so then in that case it's been oxidized and reduced I think my math checks out there then we have Redux titrations it's very similar to acidbase titrations but these titrations follow transfer of charge rather than transfer of you know uh protons or um or just pH changes then we have potentiometric titration again not too high yield but you just use the voltmeter to measure the electromotive force of a solution instead of using indicator equivalence points or sorry instead of using indicator you use the equivalence point but here it's determined by the change in voltage rather than using like an indicator or measuring pH okay now we have balancing via half reaction method so here you take both the half reactions and let me show you an example so this is kind of a context in which you have like you know what's what's happening like chromium this is the change in chromium this is the change in iron right but you know that there's some loss of electrons gain of electrons somewhere um you know that there's like one one of these is getting oxidized one of these is getting reduced so you split them up into half reactions oxidation half reaction and reduction half reactions and then if you follow the steps you can actually uh figure out the full equation for this so you know that we added protons and we added electrons and then we added water and basically now the reaction is all balanced out and so we wouldn't have been able to figure that out just based on this equation but using that whole method we found out what is the actual reaction with all the electrons and protons that are getting exchanged what is going on so just follow the steps and you'll be able to balance half reactions okay now we're on the final step which is electrochemistry and this is honestly probably the toughest uh page on this in this chemistry portion um I always had trouble with batteries and how they worked so let's talk about galvanic cells and electrolytic cells um galvanic cells is where you have like um a reduction and an oxidation part of this and based on the anode is where um oxidation is happening and the cathode is where reduction is happening and so oxidation remember is loss of electrons so the electrons go from the anode and go to the cathode and this um solution has cu2+ and then the cu2+ combines with these electrons that are going here and they form copper right and so what you're going to find is that this is actually going to gradually get thicker and thicker because more of this copper solution is becoming solid copper and joining with this bar and what you're going to find here is that this is actually going to get thinner and thinner because this zinc solid zinc is going into the solution and just becoming zinc 2+ and these electrons are going this way and then you have a voltmeter that just calculates what is the voltage that is being created by this um solution you also have a salt bridge which helps balance out the charges so you have you know this this solution you have all this positive copper that's going into here and so you have negative sulfur that's going away from here here you have all this positive zinc that's going in here the zinc exchanges and you get some sulfur that's going here so that's kind of a galvanic cell electrolytic cells is just basically very similar it's just that you have a battery in the middle and so the battery is forcing this electron flow to go to the opposite Direction and so it's important to know that anode is still the same thing it's still the place that's H oxidation is happening and cathode is still this place that's reduction is happening so here it gets kind of confusing the definition but as long as you know okay oxidation is happening here there's loss of electrons that's the anode here there's gain of electrons that's the cathode that's all you have to remember so that's kind of the difference between electrolytic and galvanic cells okay uh electron flow happens from anode to cathode like I just mentioned and then current flow if you watch the physics section I talk about how current is kind of interestingly named because current always refers to the flow of positive charges so if electrons are flowing here then that technically means current is Flowing the opposite direction galvanic cells is what I just talked about spontaneous reaction negative Delta G uh and then we have this New Concept which is e um and that's basically the same thing it's representing the same thing as um Gibs free energy it's just more specific for battery or electron situation now uh electrolytic cells are non-spontaneous positive Delta G so so like gives free energy it's kind of non-spontaneous reaction um okay now we have concentration cells and concentration cells are just specialized forms of galvanic cells in which both electrodes are made of the same material um and it's actually just the concentration gradient between the two solutions that causes a movement of charge we have rechargeable batteries and rechargeable batteries just experience changes in the situation between electrolytic and galvanic States now we have um these and they're not too high yield so I'm not going to go too much into it but we have lead acid and then these two and again not very high yield they're just like very specific types of um batteries so I'll let you read into it okay now we have cell potential so cell potential there's reduction potential and reduction potential just quantifies the T tend for a species to gain electrons and be reduced so something that is usually really really willing to accept electrons that has a high reduction potential if it does not really want electrons or usually it's a it wants to give away electrons then it has a low reduction potential so a standard reduction potential that's what this is right and it's basically um and this is e reduction and basically it's just uh a chart that tells you like okay this is very high on a reduction potential this is very low on a reduction potential so if you imagine like you wanted to create a galvanic battery and you have an anode and cathode what material would you want to use for the cathode and which one would you want to use for the anode hopefully you're thinking like for the cathode cathode is where reduction happens so I want something with a high standard reduction potential for the cathode and I want something low standard reduction potential for the anode because anode is where oxidation happens um and the way that I always remember this is that um anode starts with a a vowel and so it does oxidation cathode and reduction those don't start with vowels okay now we have standard electromotive forces so this is just the difference between the standard reduction potential of the two half cells so if we subtract the reduction potentials that's what we get and then we know that we just went over this okay uh now we are into EMF and thermodynamics and it's just important to understand like these two are very related it's just the opposite signs so um this and this basically uh there's in this equation there's a negative sign which is kind of unfortunate makes things confusing but basically when this is positive that means it's spontaneous and when this is negative that means it's non-spontaneous okay I would really try to know this equation over here that just uh that's just like the relationship between gives free energy and this uh e of sell value and uh that is a very high yield relationship and these are equations that we already talked about in relationship to gives free energy uh this is important also uh one Kum is equal to a jewel over a volt okay finally we're on ner equation nerst equation is just describing this relationship over here and this is this should make sense if you understand the relationship between Delta G and K like we talked about before but basically that's just describing the same relationship so if you understand the relationship between Delta G and E then you should understand the relation between KQ and E so KQ is greater than one then we should have a positive e if KQ is less than one we should have a negative e and if it's equal to one then this should be zero and then this is a very important equation that just relates um the Q value remember the Q is about how much concentrations do we have in our equation and the E of the cell and based on that you can figure out like oh does this want to move uh SP like does this want to move in this direction or in this direction and that's kind of what you can figure out based on this equation uh and then if we take the uh if we take what we know which is the r value and the F value over here and we simplify it then we get this over here so that's kind of what that's doing all right um that's the entire chemistry section I really hope that this was helpful to you if you have any questions feel free to leave a comment down below or send me an email um thanks so much for watching I really appreciate your time bye everybody