okay this video is going to go over a whole bunch about like 120 different regions questions actually more than that because some pages have more than one question types of regions questions that show up over and over and over and over and over again specifically focusing for the most part on multiple choice but again some of these content type questions spread out into the written questions so if you want like an overview of the most common types of questions you will see this is a great video to watch let's go through some very common region chemistry questions okay are you ready here we go which element must be present in an organic compound well you must know that organic compounds must contain this element carbon what is the number of electrons shared between the atoms in an I2 molecule well Each coent Bond shares two electrons or one pair okay so iodine you can see right here has seven valence electrons so when we draw a Lewis Dot Structure for an iodine atom it looks like this remember the leis Dot Structure only shows valence electrons unpaired electrons have to bond and if you notice this iodine has one unpaired and this iodine has one paired one unpaired so those two unpaired will pair up and form a bond okay so in a Cove valent Bond we have two electrons or one pair of electrons that are shared if there is a double bond for example look if I'm making O2 oxygen has two electrons that are unpaired that means two electrons must Bond it forms a double bond nitrogen has three unpaired electrons so it will form a triple bond in N2 okay which statement describes a benefit of using fision reactions so what do you have to know about the benefits of nuclear reactions so first of all you have to know that nuclear reactions always produce a large amount of energy like a really large amount of energy in addition you have to know the benefit of some specific Isotopes those would be carbon 14 used to date things that used to be living so like humans or plants iodine 131 that is used to diagnose and treat thyroid iodine thyroid disorders uranium 235 and 238 that are used to date rocks and minerals okay because uranium 235 and 238 have much longer half- lives and then these last two technum 99 and Cobalt 60 which are used in relationship to cancer diagnosis and treatment so again the big benefit is we get large amounts of energy what is a potential risk associated with radioactive isotopes well we have to know the risks that come with on nuclear reactions so those are things like a danger to living things radiation emissions mutations and reactor meltdowns so the one that is a potential risk is biological exposure meaning a danger to living things the results of the gold foil experiment led to the conclusion that an atom is well you have to know what the results of the gold foil experiment were it were those two results were atoms are mostly empty space and atoms contain a small dense positively charged nucleus okay which positive ion must be present in an aquous solution of an arous acid well we have to know about arenus acids arous acids found on table k release H+ as The only positive ion but I don't even see that as an answer choice so what I need to remember is that H+ typically bonds to water when it's present so H+ and h3o+ could be considered the same thing so there we go which substance is an arous base well we have to know about arous bases arous bases found on table L release O negative as the only negative ion and then we just look it up on table l in this case and we will find lithium hydroxide according to one acid base theory a molecule acts as an acid when the molecule well we have to know about the brownstead Lowry acids now typically this is referred to to as one acidbase Theory or another acidbase theory in this case they donate H+ or donate protons and there we go one acid base theory states that a base is an so again know about Brown said Lowry bases they accept protons or accept H pluses so there we go State the number of significant figures to which the given pressure is expressed so I have to know which one of these is pressure and there we go what do we have to know about significant figures we have to know that if it's not a zero it's always significant zeros are the only funky ones when a number has a decimal point we begin counting in in this direction when a number does not have a decimal point we count in this direction and we look at the first number we see is it a zero no it's significant and then once we count following in that direction we were counting every digit is significant same here that's not a zero okay everything is significant but what about here no decimal so we count this way look at this first digit it's a zero skip it aha finally not a zero so we end up with two so in this case how many significant digits do we see here there's a decimal start this way yeah we see three which element has an atom with the greatest tendency to attract electrons in a chemical B well you got to know the definition of electr negativity which is the ability of an atom to attract an electron in a bond so we have to look up the values for electr negativity on table s and we're just looking for the biggest number so in this case is going to be chlorine a collision between reactant particles is most likely to result in a reaction when the particles have proper orientation and proper we got to know about Collision Theory right effective collisions occur when particles collide with proper energy and orientation so that means the particles collide with enough energy and lined up correctly so yeah there's our answer explain in terms of collision Theory why reacting hydrogen and nitrogen at high temperature increases the rate of the reaction well you have to know how to increase the rate of a reaction we increase the rate of a reaction by increasing the number of effective collisions so when we increase the temperature okay there are more effective collisions why the particles are going to collide first of of all more often and second of all with more energy catalysts can increase the rate of a chemical reaction by providing well we have to know how catalysts affect the rate of a reaction catalysts increase the rate of a reaction by lowering activation energy and providing an alternate pathway a shortcut so it looks like this this is with a Catalyst to see how our pathway changes and the activation energy goes down there we go which sample of HCL aquous reacts at the fastest rate with a 1 G sample of iron Fates we have to know ways to increase the rate of a reaction so we can increase temperature we we can add a catalyst we can increase surface area that means make tiny pieces or we could increase concentration so when we're looking here we want the high temperature and we want the high concentration right so there we go according to the kinetic molecular theory Which statement explains why an ideal gas can be compressed to a smaller volume well so we have to know the kinetic molecular theory for ideal gases what does it State gas particles are small super tiny their volume is negligible they have no attractive forces they transfer all their energy in collisions their collisions are elastic they move rapidly they move randomly they move in straight lines so which one of these allows them to be compressed squished into a smaller volume well that would be it the gas particles are far apart all right as the elements in Period two are considered in order from lithium to Florine there is an increase in the well we have to know the periodic trends across a period now we use table s to look up the numbers so if I'm looking for Period 2 I'm just going to look at the first three elements in Period 2 and look for a pattern but what you will see across the periodic table when you go across a period atomic radius will decrease electr negativity will increase and first ionization energy will increase so this one is electronegativity as the first five elements in group 14 are considered in order from top to bottom there are changes in both the okay so first of all we have to know the periodic trends down a group use table s again I would look at the first three elements in a group and see what the patterns are but you should see that atomic radius will be increasing electro negativity will be decreasing and first ionization energy will be decreasing the last thing that's mentioned here is the number of valence shell electrons well in a group okay which in in uh valence electrons the last number is valence electrons and down a group the valence electrons stay the same so it's this the element in group 14 period 3 of the periodic table is classified as a okay so group 14 this way period three this way it's this element what is it we have to know the locations of those metals non-metals and metalloids yeah it's a metaloid which list of elements includes a metal a metaloid and a noble gas okay well let's look does this one have a noble gas yes it's Neon right does this one have a noble gas yes radon does this one have a noble gas yes Neon oops and radon two noble gases does this one have a noble gas no cuz remember noble gases right here in group 18 so now I have a 50/50 chance so let's see about a metaloid remember metalloids are in between metals and non-metals right and they touch that vertical line of the staircase so Boron we skip aluminum that's the only Oddball that one is a metal so then we have silicone geranium Arsenic and so on so let's look at Choice two do we see a metaloid let's box them yes okay what about in one do we see a metaloid no cuz rubidium is here and chlorine is here so our answer is this which element is Mal valuable at STP well you have to know properties of metals so metals are malleable which means we can Hammer them into sheets ductile we can stretch them into wires they're good conductors of both heat and electricity they have electrons in a mobile sea of electrons uh those are metals they lose electrons and they form I I iic bonds with nonmetals so I'm just going to look it up on the periodic table for that question and find the one that is in fact a metal now this question says which compound has coal bonds and what you'll see is we have metal nonmetal metal non-metal metal non-metal so those would all be what ionic bonds so the one that has coent bonds has to be the Oddball you know one of these things is not like the others like that which is a property of most nonmetallic solids so we have to know the properties of nonmetals so non-metals are brittle they're dull they're poor conductors they gain electrons they form ionic bonds with metals and then they form Cove valent bonds with other non-metals so what do we see as our answer yes there we go which sample can be classified as a substance well we have to know the two types of substances and those are elements and compounds okay so we can see that all matter is either a pure substance or a mixture a mixture is either homogeneous or heterogeneous but a substance is either an element or a compound and so that one is one that is found on the periodic table of what oh of elements which element has chemical properties most similar to sulfur well we have to know that elements in the same group share similar properties they share similar properties because they have the same number of valence electrons so we're looking for sulfur right here so elements that are similar to sulfur in terms of chemical properties will be in that same group that same vertical column and you can see in this case it is going to be oxygen given the equation representing a system at equilibrium which change will cause the equilibrium to shift to the right okay we have to know lha T's principle and lusa's principle says that when a system at equilibrium is stressed it will always respond in a way to relieve the stress okay so reactions at equilibrium always respond perfectly also as a side note catalysts never ever ever affect equilibrium so this first answer I know is wrong all that a catalyst will do is increase the rate of the forward and reverse reactions but will not affect the equilibrium okay so if I increase so here I'm increasing pcl3 if I increase this all right how does the system respond to that stress it says oh no we have too much pcl3 what do I have to do use it up right that's how I relieve the stress now if I look here I have two sides of the equation right so everything that is on the same side as PCL 3 three will also decrease and then the reaction will shift toward this side and make more of it is that the way I wanted the reaction to go no it is not great all right try the next one increase the pressure okay this is a good one for pressure what matters are gases and I have to count okay so this is a gas what coefficient is in front nothing so there's one mole of that that's it that's the the only thing on the reactant side when I go to the product side I have one mole of this and one mole of this so I have two total moles so when I increase the pressure think about it like this that's low pressure here's high pressure when I increase the pressure I have less space so the smaller number fits better that's this one right so the reaction will shift toward oh great it's also going to the left side well this one better work let's try it out let's just uh switch our pen color so it looks a little less confusing let's increase temperature where is temperature represented right here energy how do we fix the problem of having too much temperature or too much energy I want to decrease it right everything else on that same side will also decrease everything on the opposite side of the equation will increase and the reaction shifts toward the side where there's an increase so finally we get to Tada that is the answer which substance cannot be broken down by a chemical change well you need to know that elements cannot be broken down chemically okay compounds can be separated chemically and mixtures can be separated physically so that's kind of important things to remember so when it says which cannot be broken down by a chemical change I'm looking for the name of an element if you don't remember the name of the element because you panic on the exam look at table s and start scanning down the list of elements until you will find this one which sample of matter cannot be broken down by a chemical change again we're doing the same thing but if you don't recognize the name of the element right away that's okay use table s scan down the list until you find there we go which equation represents a physical equilibrium okay you should know the difference between physical and chemical equilibriums okay um what does that mean well in a physical equilibrium the system has undergone a physical change in a chemical equilibrium it has undergone a chemical change also just about equilibrium in general equilibrium occurs in a closed container and the reaction is reversible so what I'm doing in this question here is I'm looking for something that has the same exact chemical formula on both sides okay and which statement describes ice and liquid water in a stoppered flask at 0 degrees CSI at equilibrium so stoppered flask tells you it's a closed container right it tells you it's at equilibrium what else do you have to know about equilibrium at equilibrium rates are equal and concentrations are constant so I'm looking for something that fits that description and there we have it again as a reminder for equilibrium the reaction must be reversible it must must be in a closed container and the rates are equal of the forward reaction and the reverse reaction and the concentration of the reactants and the products must be equal so one additional thing since the reaction has to be reversible notice that choice one this is not reversible and choice three this is not reversible so those should have been eliminated from the beginning okay which substance can be broken down by a chemical change well again you should know that compounds are combined chemically and therefore can be broken down chemically so the only one that is a compound meaning it is not on table s okay is this one now which substance contains elements combined in a fixed proportion or definite ratio well compounds are combined chemically in a definite ratio again I'm looking for the Oddball the one that is different the one that is a compound not an element so I'm looking for the one that is not going to be found on table s given the equation representing a system at equilibrium which stat describes the concentration of the two gases in this system well do you remember already you have to know about rates and concentrations so equilibrium requires a closed container and a reversible reaction the rates are equal and the concentrations are constant and what concentrations are constant the concentration of the reactants and the products so there we go given this key right which particle diagram represents a chemical change so you have to know the difference between a physical change and a chemical change so in a chemical change the substances on both sides of the chemical equation are different so if I look here this has all element a on this side and all element a on this side that's physical all element Z on this side all all element Z on this side physical okay let's look here we have a and b combined on this side A and B combined on this side right this one we have a combined with two Z's a with two Z's and then over here we have two Z's and two A's combined so this is going to be the chemical change why because the chemical formulas are different on both sides the remaining three 1 through three are all physical changes nothing changed about the chemical formula the chemical formula here is just single a this is just single a this is single Z this is single Z this is a with z and this is a with Z this is a with two Z's this is A2 and Z2 so you see how the chemical formulas changed all right which statement describes a chemical property of iron well you need to know the difference between physical and chemical properties physical properties can be identified without changing the substance so that means I can just look at it or I could do something to it but it's still the same thing so for example iron is malleable that means I can hammer it out into a thin sheet if I hammer it out into a thin sheet will it still be Iron yes absolutely okay iron conducts electricity if I run electricity through iron is it still iron yes absolutely and what about this one iron has a high melting point if I melt iron is it still iron yes absolutely so the key word here is reacts when iron reacts with nitric acid that indicates a chemical property okay so which sample at STP has the same chemical properties as 10 gr of Al at STP well whatever aluminum's chemical properties are it will have the same chemical properties as an additional sample of aluminum so if it has the same chemical properties it's literally the same diamond and graphite are two forms of solid carbon these two forms of carbon have so we have to know what allotropes are allotropes are forms of the same element with different structures and therefore different properties so if you see if it has the same structure it cannot have different properties okay if it has different structures it can't have the same properties properties different structures yields different properties okay the melting of an ice cube is an example of an well we have to know if changes of state are exothermic or endothermic also you should know that phase is another word for state so change of phase or change of state okay exothermic remember meaning energy is Rel leased it is a product endothermic meaning energy is absorbed it is a reactant okay so you have to know the names of the changes of state okay now the ones that are easy to remember are liquid to gas because that should be familiar um gas to liquid that should be familiar solid to liquid that should be familiar and liquid to solid now the new ones that may have been introduced this year are these two the one that is most often tested is sublimation that is going from a solid because sublimation starts with the letter S to gas okay so solid straight to gas right so if we think about it in order like this going from solid to liquid to gas as we move this way from solid to liquid to gas we have to add energy in so that that means it is endothermic I always remember in order to melt something you have to add energy right that means to go in the reverse direction from gas to liquid to solid is exothermic meaning energy is released so when you know all of that you should be able to determine that melting fits this answer Choice the arrangement of particles is most ordered in a Le of well you have to know how solids are ordered crystalline crystalline and have the least motion and strongest intermolecular forces so some key information to know about the states of matter solids the particles are close they're in a regular pattern often described as geometric they vibrate so they're moving but moving slowly they have the a lower energy and in their 2D diagram you can see that the particles are ordered and very close together in a liquid the particles are still close they're a little bit more randomly arranged because they can move around each other and slide past they have more energy and they're going to have more Motion in a gas the particles are far apart they are much more randomly arranged they move quickly randomly in straight line Motion in all directions they have a high amount of energy and they are far are apart so this we could say the volume and the shape are fixed here the volume is fixed but the shape is variable and lastly here both the shape and the volume are variable okay so where is it most ordered we're just looking for the state of matter in which 1 point0 G sample are the particles arranged in a crystal structure again we're just looking for the solid simply based on table F which 10 G Sample When thoroughly mixed with one liter of water at room temperature forms a heterogeneous mixture so we have to know how to use table F on table F if it is insoluble it is going to be a heterogeneous mixture if it is soluble it is homogeneous often called aquous or a solution so let look up what we have nh4 that's right here that is always soluble wrong answer potassium iodide well K if you don't know I sort of hate this about this table K is in group one but we could also look it up here right and P is not one of these exceptions so that means means I stays soluble okay silver bromide all right so bromide right here oh but look at this look at this exception right this exception means soluble breaks its rule it is insoluble so that looks like it's the answer let's double check both Na and NO3 are always soluble so yes it is that word which phrase describes the nucleus of any atom okay well we have to know how to determine the charge of a nucleus so the nucleus contains protons and neutrons the number of protons or the atomic number determines the charge why because protons are positive and neutrons are neutral so the neutrons do not contribute to the charge of the nucleus so obviously that means the nucleus has an overall positive charge and then we have to determine the net charge okay now it could be for an atom but it could be for an ion what is the net charge of a monatomic ion and it has these subatomic particles so we have to know that protons are positive so we have 15 positive right neutrons are neutral so they don't count and we have 18 electrons and electrons are negative so what is that overall charge yep there we go all atoms of the element vadium must have the same well you have to know that the number of protons determines the element so the number of protons is the same as what the atomic number a pottassium atom has a mass number of 37 what is the number of neutrons in this atom well I have to know how to determine the number of neutrons so the number of neutrons plus the number of protons equals the mass number so mass number in isotope notation gets written here atomic number gets written here we find neutrons by subtracting so the symbol for pottassium is K his mass number is 37 how do I find his atomic number I look it up on the periodic table how do I find the number of neutrons I do that math which symbol represents a nuclear emission with the greatest mass and the greatest ionizing power well we have to know the ionizing power of nuclear emissions the particles with the gra greatest mass greatest charge will have the greatest ionizing power so it can hit boom with enough Force to remove an electron so where would I look I would look at table o to find the mass of those particles but in general anytime we're talking about big particles and we're talking about emissions we're talking about Alpha okay so that is the answer but table o will help plus looking for the bigger numbers that has the greatest ionizing powder now when we're talking about radioactive emission with the greatest penetrating power but the least ionizing power so we have to know about penetrating power in this case the particle with the least Mass has the greatest penetrating power why because it's so itty bitty bitty can get through more things okay so in this case alpha particles are big so they don't have a lot of penetrating power and gamma radiation which has no mass and no charge is able to get through many more things all right the elements of the periodic table are arranged in order of increasing well we have to know how the periodic table is organized it's in ranged in order by atomic number that's just you got to know it well you can look at the periodic table and see it too all right which Lewis dot diagram represents an atom of nitrogen in the ground state well we have to know how to find valence electrons so valence electrons are the last number in the electron configuration on the periodic table leis do diagrams only show valence electrons so when you look up nitrogen it has five and whether they ask the question like this where you find the ls dot or like this where you just have to pick the number Krypton atoms in the ground state tend not to bond with other atoms because they're well know how many valence electrons atoms want to have okay atoms want the electron configuration of a noble gas noble gases tend not to react so what does that mean either eight valence electrons like most noble gases or with one exception two total like helium not two Valance just two total because the first energy level only holds two electrons so helium has a full valence shell but in the case of Crypton it is the outermost shell or valence electrons are eight okay identify three endangered elements listed in the passage that are classified as Metals well that means we have to know the names for the main group elements or the locations of metals non-metals Etc so this is a place where I'm just going to choose to excuse my cat seriously are going to choose to review the names of these groups you have to know group one is alkaline metals group two is alkaline earth group 18 is noble gases Group 17 is halogens and you find transition metals here but in general metals are everywhere over here on the left side with the exception of hydrogen which is a non-metal the non-metals are on the right side and then the metalloids in between okay so when I look these are the elements I have to choose from I find them all on the periodic table helium right zinc gallium indium and what else do we have torium now what are the three that are metals yeah those three given the bright line Spectra of four elements and the spectrum of a mixture formed from these two elements which two elements are present in this mixture well we have to know how to interpret bright line Spectra right right line Spectra are produced when electrons fall back from excited state down to ground state and when they do they release or emit energy as light for elements to be present in the mixture all of the lines for that element must be present in the mixture so I tend to look for double lines so for example here element G has a set of double lines look at the mixture element G is not there oh I'm down to a 50/50 okay what else we have a double set right here right go down oh that is not in the mixture e okay now I have no e and no G which means the remaining two must be in the mixture right a sample of KCl solid is dissolved in water to form KCl aquous when the water in the KCl aquous is completely evaporated KCl solid remains which statement describes a property of the KCl solid after the water evaporated what do you have to know that substances in a mixture keep their properties so it still has the same melting point or if powdered iron is magnetic but powdered Su sulfur is not what occurs when they form a mixture in a beaker at room temperature yeah the iron is still magnetic in a mixture the substances keep their properties okay which changes in both charge and radius occur when an atom loses an electron okay let's think what happens to the size of an atom when it becomes a positive ion why would it be positive because it's losing an electron an electron is negative so when you lose a negative you add positive right so electrons are negative so when atoms lose electrons cat ions or positive ions are formed okay now here's the atom say it had eight electrons as an atom okay and then it gains two electrons and now it has 10 right so it added in two electrons what would happen to the size yeah but what about if I talk about an element that has 11 electrons right and it loses an electron and now it has 10 what would happen to the size yeah it would get smaller right so smaller compare the radius of a fluoride ion to the radius of a fluide atom so again we have to know what happens to the size of an atom when it becomes a negative ion so electrons are negative so when they gain electrons and ions or negative ions are formed okay so what happens when you gain electrons the radius of the fluoride ion is larger than the atom why because the atom gained electrons so here let me just stress something really important the atom is the one losing or gaining the ion is the result after so you do not say the ion lost or gained you say the atom lost orgate literally my cat that's Phoebe so in case you hear phoe is being very vocal right now so just to go back to that the atom is what loses or gains the electrons I always see someone who will write an answer incorrectly and say the ion lost not true the atom loses or the atom gains an electron date in terms of aquous ions why this tap water can conduct an electric current so you have to know the definition of an electrolyte an electrolyte conducts electricity when dissolved in water so electrolytes can be one of three things an acid a base or a salt acids or bases are found on a table K and table L but also organic acids count and those are going to be listed on table R and sometimes that's throw in as a trick okay uh and then salts we're going to look for something that is a metal and a non-metal or something that involves a polyatomic ion but why do they conduct electric current well they conduct electric current because the ions can move so electricity requires moving charges right specifically we have electrons moving around so in order for water uh tap water in particular to conduct electric current it has to have dissolved ions that can move because pure water does not conduct electricity tap water will because it has dissolved ions why is potassium nitrate classified as an electrolyte because it releases ions right when it's aquous given the equation representing a reaction this equation represents what well we have to know the types of nuclear reactions so we have transmutations transmutation is when one element changes into another so you see that happening here we started with hydrogen and we ended with helium so it's definitely a transmutation now if it's a natural transmutation we have only one reactant so that means a is going to end up with a couple things on this side if we have an artificial transmutation typically we hit something with a neutron and then on the other side we will have uh usually a couple of smaller things and then perhaps some neutrons again but the big thing is is that artificial has two reactants or natural has one and then we have Fusion which is joining together to little nuclei and then we have fision which is splitting a big nucleus so the one we see there is yeah Fusion which nuclear equation represents a spontaneous Decay spontaneous is natural it just happens that means it's just one thing and just falls apart so that's the only one that has One Singular reactant number three is an example of fions when I talk about a big nucleus being hit typically with a neutron and falling apart okay a student measures the mass and volume of a sample of aluminum at room temperature and calculates the density of aluminum to be 2.85 G per cubic cm based on table s what is the percent error for the students calculated density of Al well we have to know how to calculate percent error the formula is on table T and you often also need to use table s in this case here is the formula on table s when we look up the density of aluminum we find this so our measured value is here that replaces this our accepted value is here and here so we get this and when you do this in the calculator so let's show you okay we have 2.85 minus 2.70 and that's in parentheses so let's enter to get equals right now we'll divide that by 2.7 equals and then we'll multiply that by 100 and you can see our answer is going to be right there all right given the equation for this reaction which type of reaction well we have to know the types of organic reactions so PS faces right here this can help you remember the seven organic reactions in polymerization we have many monomers many many many many small molecules joining together to form a larger polymer in saponification we get soap and we need a base a strong base like NaOH for example in order for it to happen fermentation produces alcohol and CO2 bubbles okay addition is when we have two atoms added combustion is burning so we get carbon dioxide and water as the products aerification makes an eser so table R will help us here and substitution is when we get one atom swapped for another okay so let's look here right now we have four carbons and 10 hydrogens on this side we have four carbons and nine hydrogens and a CL what happened yeah there was a swap One Singular Swap and then which type of reaction produces soap saponification it l literally looks like soap just the first four letters are scrambled all right given the equation representing a reaction which type of reaction does this equation represent you have to know the types of chemical reactions so here are the four types so we had the organic ones right but these are just in general chemical reactions so synthesis is building so starting with two ending with one chemical formula right decomposition positions start with one chemical formula end with two single replacement we have a single element on both sides so this is like you know A and B were a couple and then C uh steals a and now they're dating and B is sadly alone okay double replacement is kind of like WIP swap okay I don't know if you ever seen that show but um see A and B are together and on this side a a is partnered now with C okay so in this equation what do I have I start with one thing and I have two on this side yeah that's decomposition Which statement represents neutralization so we have to know the neutralization reaction it means we start with an acid and a base as the reactant and then water and ass salt will be the products so we start with an acid and a base and we get water and a salt so the H from the acid and the O make the water and then what's left makes the salt okay under which conditions of temperature and pressure does a sample of propane behave least like an ideal gas well we have to know when and I when I gas is more ideal okay so ideal gases like tropical vacations they love high temperatures they love it warm and they love low pressure also low stress right so when will it behave least like an ideal gas when would that be well that would be when the temperature is low like that and the pressure is high like that so least like an ideal guas would be here what would it be if the question said most like an ideal guas if it said most it would be this one high temperature and low pressure so just be careful when you're reading the question so you know exactly what you're supposed to answer a structural formula differs from a molecular formula in that a structural formula shows the so you have to know what a structural formula is here are some examples so this is a molecular formula this is a structural formula molecular structural molecular structural so what does structural do yeah it shows the arrangement of the atoms which electron configuration represents the electrons of an atom in an excited state well we have to know how to write an excited state electron configuration but for this question what we really have to know is that ground state configurations are found on the periodic table and an electron in an excited state is higher than it's supposed to be in ground state so if it's excited state it won't be on the periodic table so here's one of those one of the things is not like the others find the one that's not on the periodic table and it has to be excited state two atoms that are different isotopes of the same element have well for this you need to know the definition of Isotopes Isotopes are the same element that have the same atomic number but different Mass numbers same number of protons but a different number of neutrons okay same number of protons but a different number of neutrons how would I recognize them they have to be the same element because they have the same number of protons right so same element but a different number of neutrons same atomic number but different mass number which subatomic particles are matched with their charges well you have to know the location the mass and charge of all three subatomic particles so here they are now table o can help you it lists everything except for the location if you know for example on table o proton looks like this okay Mass like charge like this if you know that that is mass and that is charge okay Neutron looks like this mass and charge right on table o again okay but location you have to remember so electrons are located in electron shells or electron levels or energy levels or energy shells in uh shapes called orbitals right that's where they're located protons and neutrons are located in the nucleus and then charges now remember electrons truly do have a mass we call it zero to make the math easier but in reality it's about one uh 2,000th of a mass of a proton and a neutron so this is the one that matches up correctly which particle diagram represents a sample of oxygen gas at STP you have to know how to recognize the datomic elements so what are they I remember the phrase brinkle Hoff bromine iodine nitrogen chlorine hydrogen oxygen and Florine exist as datomic which means they exist bonded together as pairs so when I'm looking for a sample of oxygen gas first I know it's a gas so this is wrong this is a liquid this one was a solid this one is a liquid but these two are both gases which one has is has to be oxygen then yeah the one that is diatomic which two particle diagrams represent two different phases so remember that phases means states of mass matter okay so two different phases of the same compound only well we have to know how to interpret particle diagrams so if it's a compound that means atom of one element and atom of a different element have to be combined so you can see this one has two of the same so that's an element so that's not and then this is different right so that can't be right and you see that here as well so we see this and this I'm looking for something that has only the same compound in it and here you can see this would be a gas and this would be a solid so two phases of the same compound where we have one dark circle and one light circle bonded that's in in both diagrams two liquids can be separated by distillation due to a difference in well we have to know how to separate a mixture so we can use distillation to separate two liquids based on their differences in Boiling Point okay we can use evaporation to separate a dissolved solid right so that's based on solubility so we can boil away the water we can use chromatography to separate dyes based on differences in polarity and particle size and we can use filtration to separate an undissolved solid and that's based on solubility and particle size so for our question it is yeah boiling point which sample of matter can be separated into two different substances by physical means well we have to know that mixtures are combined and then can be separated physically we also need to know that Solutions seen most often with AQ are homogeneous mixtures why the salute whatever the substance is NAC for example is dissolved in water so for these questions we're looking for the thing that identifies a mixture so this is simply not just magnesium sulfate it is magnesium sulfate dissolved in water so which sample of matter is a mixture not just magnesium chloride it is magnesium chloride dissolved in water a mixture which statement describes the earliest model of the atom so you have to know how the atomic model changed over time with Dalton it was a solid sphere with JJ Thompson who did the cathode ray experiment discovered electrons so thought these negative electrons were kind of stuck in this positive ball like a cookie dough the Rutherford model came out after the gold foil experiment and that atoms were mostly empty space with a small dense positively charged nucleus and then the current model called the electron cloud model or the modern model or the wave mechanical model is that electrons are found outside the nucleus true but in an electron cloud in shapes called orbitals so what was the earliest yeah the wave mechanical model of the atom describes the location of electrons so we have to know the location of electrons their electrons are located in orbitals these specific shapes outside the nucleus orbitals not orbits so be careful sometimes they throw the word orbits in all right so which numerical setup can be used to calculate the atomic mass of the element copper so you need to know how to calculate atomic mass you should also know that the definition of average atomic mass is that it's an average based on all the naturally occurring Isotopes and we use atomic mass and percent abundance to calculate so we need to multiply this atomic mass times this percent this atomic mass times this percent and then when we get that those two answers we will add them up however since it is percents we should know that we can't really do math with percent until we change them into a decimal so this right here for number one it would be right if it was this times well this wouldn't be right anyway because look it's paired up incorrectly this one on the other hand has 62.93 paired with 6915 that would be correct if it had a percent symbol after it meaning that you knew that you had to change it to a decimal but it doesn't so it's also wrong so this is it uh translated into a percent how do we translate I mean translate the percent into a decimal how do we do that we divide it by 100 so you can just divide both of these by 100 that converts it into a decimal so we can do the math and there we have it no this one is not paired correctly right this one right here 62.93 needs to be with this percent abundance right this is the correct answer okay right here which net change occurs in both nuclear fision and nuclear fusion reactions well we have to know that in nuclear reactions a small amount of mass is converted to energy as a result all nuclear reactions produce a huge amount of energy more than any other kind of reaction so if it was like which type of reaction produces the most energy it would be a nuclear reaction so mass is converted into energy in all atoms of bismuth the number of electrons must equal the so you have to know that atoms are neutral neutral right which means the number of protons which has a positive charge must equal the number of electrons that have a negative charge which electron shell in an atom of calcium in the ground state has an electron with the greatest amount of energy so we need to you need to know how to determine which electron has more energy so electrons further from the nucleus have more energy so picture it like this so here's the nucleus in the center and then we have energy levels surrounding so energy level one 2 3 4 and so on so imagine it like this here's the nucleus and we're holding a rubber band that far from the nucleus and we let it go and that's how much energy the first electron shell has and then we do the same thing for the second energy level and we let it go and then we do the same thing for the third electron um energy level we pull the ruband out that for far and then we do the same thing for the fourth one where would I have the most energy well if I let go from right here that would hurt the most right okay so let's look at calcium it has two electrons in energy level one eight electrons in energy level two eight electrons in energy level three and two electrons in energy level four four so which one has the most energy yeah the electrons in energy level four not because there's two of them simply because they are furthest from the nucleus which formula represents calcium hydde okay let's see how we figure that out we need to know how to write a binary formula so sometimes we need polyatomic ion so let's look we can see this all has calcium right and then either it's calcium with H or calcium with o so if we look here on table o there's I mean table e there's o and its name is hydroxide well that's not what this says so now these two are wrong so now I need from the periodic table calcium and hydrogen look at calcium's charge it's Plus two um and hydrogen if calcium is plus two hydrogen has to be -1 right but if a calcium is + two and hydrogen is -1 if I add those two numbers together will I get zero no no no I will not so I need two of those so Tada let's do it similarly with chromium what does this this mean three right plus three because the first element is always positive the last element is negative okay so let's look at chromium and let's look at oxygen we can see that it's chromium 3 right so it's chromium + three and oxygen minus 2 if we add those together will they balance out and equal zero no they will not let's add another chromium that gives me plus 6 Al together and then if I do this with oxygens and I make minus 6 now will I they add together and make zero yes so I write chromium how many chromium did I need two o how many oxygens did I need three and voila now what is a chemical name of the compound C so we need to know how to write the name of a compound okay so again let's look at polyatomic ions but you can see here this is simply just CU and S so I have these options right now you can see that either it's going to be copper 1 or copper 2 and it's either going to be sulfide or sulfate so let's see if we can eliminate an some answers well you can see that it's c if it was sulfate it would be this it's not that okay so it's either copper one or copper two how am I going to know which one well for the last element we typically use this first charge especially when it's a non-metal so if CU is -2 I mean s is -2 and then we have CU so s is -2 and then we have cu and there's one CU what does CU have to be yeah plus two what is the chemical formula for sodium oxalate well we can see here that's oxalate so c24 -2 and na is + one so I need to add another one right cuz I need it to be plus two to balance that -2 so ends up being that given the balanced equation representing a reaction what is the mass of KCl produced when 24.5 1 G of kcl3 reacts to completely to produce 9.60 gam of o2 now this is a much easier question than some people might think so it says we have 24.5 1 G of this we get 9.60 gam of o2 I want to know how many grams of that I get well it's literally just simple math because in conservation of mass I must have the same mass on both sides so I need that amount of mass to be from the KC L which equation represents a con conservation of atoms so let's look for example I have one TI perfect one TI love it two o2s 2 * 3 is 602s negative 1 TI 1 TI Beautiful Love It 202s 2 * three again come on right three TI three TI okay 3 * 2 is 6 O's 2 * 3 is 6 O's okay 2 a L's 2 * * 2 is four all right three TI yes two 3 * 2 is 6 O's 2 * 3 is 6 O's four als's 2 * 2 is four ding ding ding we have a winner finally which equation represents conservation of charge okay well let's think about it we have to know that charge is conserved in a chemical equation just like mass is conserved just like energy is conserved okay so how do I find which one has conservation of charge I want the charge to be equal on both sides so for example this is Nega one that's -2 this is zero that is not close to balanced 0 -2 -2 that's -4 H come on now all right 0 -21 oh come on -20 -2 ding ding ding we got it one mole of bromine gas has a mass of what well you need to know how to calculate molar mass formula mass gram formula mass okay that means we need the symbol from the periodic table we can see that this is its atomic mass but we have two of them right so I have to multiply that number times 2 so I do 7994 * 2 and I get this which you can see is obviously going to be um this answer right okay now what if it was something like H2 o4 okay I'd have two h's so whatever H is I have to multiply it by two plus I have one s so whatever s is and then Plus 4 time whatever o is right okay that's how you do it given the balanced equation for the reaction of butane and oxygen how many moles of carbon dioxide are produced when five moles of butane react completely so we have to know how to do mole ratio calculations so butane right here carbon dioxide right here right so normally I get two moles of butane or eight moles of carbon dioxide right butane carbon dioxide but I don't have two moles of butane I have five and I want to know how many moles of carbon dioxide so now let's cross multiply 8 * 5 is 40 equals 2 x right okay and then divide both sides by two and then we get 20 moles equal x okay now given this balanced equation the mole ratio of n o what is the coefficient in front of no to NO2 what is its coefficient well we reduce it what do that reduce to yeah one to one all right what is the percent composition by mass of nitrogen in the compound nh4 okay so we need to know how to determine percent by mass so we use this formula okay and we also need to know the mass of nitrogen and of hydrogen I have the whole thing that's the gram formula mass so that's 32 that's mass of whole what is the mass of the part well let's look nitrogen there are two of them in this formula nitrogen one nitrogen is 14 so 2 * 14 time 100 right so let's pull up the calculator and we will do 2 * 14 um I'll use the whole number just to show you that you can you can round to a whole number but you don't have to okay and then I'm going to divide it by 32 and then I'm going to multiply it by 100 and what do you see you see that that number is closest to what there a solution contains 25 G of K3 dissolved in 200 g of H2O which numerical setup can be used to calculate the percent by mass of kn3 in this solution okay again now you may think you need these but this is a little bit different so the whole thing is the solution and the part is the kn3 so K3 is the part now here's where some people get mixed up okay it says the solution contains this and this so the solution is that 200 the water plus the 25 right and then I have to do times 100 so which one of those looks correct yeah there we go all right the empirical formula for a butane is well I need to know what an empirical formula is it shows the lowest whole number number ratio in the subscripts so for example uh H2O its ratio is 2 to one that is empirical but H2 O2 right its ratio is 2:2 molecular so it's empirical would be 1: one or just ho okay but I need a little bit more information to do that for buttin first but four carbons okay C4 now I need table Q in in means this is the chemical formula so I have four carbons so I have double that for hydrogens h8 that's molecular what would that reduce to so the ratio is 4 to8 what would that ratio reduce to well I would divide both of those by four and I would get this what is the number of moles of CO2 in a 220 G sample of CO2 well I need to know how to determine moles so I need this formula okay I don't really need this because of everything I need in the question so given Mass 220 / by Gram formula mass right here so 220 / 40 oops 220 divided by 220 / by 44 there we go clear this for next time was five the particles in which sample have the lowest average kinetic energy well I need to know the definition of temperature and temperature is a measure of average kinetic energy so the lowest average kinetic energy means the lowest temperature and the average kinetic energy of the particles in a sample of matter is expressed as yes temperature what is the amount of heat required to melt 43 G of solid magnesium oxide at its melting point the heat of fusion is 1.9 * 103 Jews per gram so we need to know how to do a heat of fusion calculation here are the formulas here's the one for heat of fusion so heat of fusion is masstimes heat of fusion so the mass is 43 times the heat of fusion so what I would do is move this over one 2 3 so that's 1900 okay let's get our calculator 43 * 1900 equal this so which answer do you think it is yeah literally this one right okay solid aluminum has a specific heat capacity of 0.9 0.90 Jew per gram Kelvin how many jewels of heat are absorbed to raise the temperature of 24 G of aluminum from 300 Kelvin to 350 Kelvin so we have to know how to do heat calculations with a temperature change so this time it's this formula okay so what is our Mass 24 times the specific heat 0.90 times the change in temperature so 350 minus 300 right so let's clear this let's do 350 minus 300 right that's 50 times9 time 24 and which one is that closest to what will that round to yeah that one all right what is the amount of heat absorbed when the temperature of 75 G of water increases from 20° C to 35° C okay so uh well the mass right is 75 times the specific he it's not there aha but table B thank you table B 4.18 times the change in temperature 35 minus 20 okay so let's do this uh calculation so we have 35 - 20 * 4.18 * 75 equals so which one is that closest to yeah there we go now when would we use heat of vaporization when we're talking about a change of state from liquid to gas heat of fusion is either from solid to liquid or liquid to solid heat of vaporization is liquid to gas or gas to liquid this one only when there's a change in temperature at STP which property would be the same for 1.0 ler of helium and 1.0 ler of argon well we need to know avagadro's law and that states that the same temperature and pressure equal volumes of gas have equal number of particles so I like to think about it like balloons if I have gas gases in balloons that are the same size and they're at the same temperature and at the same pressure they have the same number of particles inside the balloons okay a cube of iron at 20° C is placed in contact with a cube at 60° C which statement describes the initial flow of heat between the cubes well so we have to know the direction of heat flow it always flows from warmer to colder so which one is warmer copper which one is colder iron which graph shows the relationship between pressure and Kelvin temperature for an ideal gas at constant volume you have to know the relationship between pressure volume and temperature so this one is pressure and temperature as we increase pressure temperature um increases or as we increase temperature pressure increases but if we're talking about um let's see temperature and volume as we increase temperature volume increases but when we talk about pressure and volume it's like this okay this would be true if that word said volume okay that would be the relationship a rigid cylinder with a movable piston contains a sample of hydrogen gas at 330 Kelvin this sample has a pressure of 150 kPa and a volume of 3.50 L what is the new volume of the sample at STP okay so I need to know how to do combined gas law calculations all right so here's my formula let's make my list of variables P1 V1 T1 T2 V2 T2 okay this T1 330 the temperatures had to be in kelvin but they already are pressure 150 volume 3.50 what is the volume at STP well I look it up on table a 273 Kelvin and then we have 101.3 kPa that came straight from table a on the reference tables okay now let's substitute so we have 150 3.5 3.5 Z but 3.5 is identical for calculations over 330 equals 101.3 right times V2 over [Music] 273 all right so so um we can just cross multiply uh we could you could do this a bunch of ways you could do this math over here um I just like to always just be consistent and cross multiply so what I'm going to do all right instead of rewriting all the numbers down watch 150 * 3.5 * 273 equals 143 325 so 14 43 325 equals V2 * right now I need to do 330 * 101.3 and that's 33429 now what do I need to do divide both sides by this 33429 so I do 143 325 / 33 429 and I get this which answer is that closest to H what do you think yeah there we go which type of bond forms when electrons are equally shared between two atoms so you have to know what happens to electrons in metallic ionic and calent so in metallic bonds electrons are in a mile CA of electrons in ionic bonds electrons are transferred and in coent bonds electrons are shared they are shared equally in polar coent bonds and they are shared they are shared unequally in polar Cove valent and they shared equally in nonpolar coent so again I started to misspeak there they are shared unequally so we have partial positives and partial negatives in polar and they are shared equally in nonpolar Co valent okay which element has metallic bonds what do you think you're looking for silly a metal right so you just find the metal all right when the nucleus of an atom of neon 19 decays which particle is emitted well we have to know how to interpret table n so find neon 19 here we go which particle oh what is that aha use table o and you will find there it is which terms represent two categories of compounds so you have to know the two types of compounds they are ionic and Cove valent but coent has another word molecular so it's ionic and coal or ionic and molecular a solution is prepared using 0.125 gam of glucose in enough water to make 250 g of total solution the concentration of the solution expressed in parts per million is well we have to know how to calculate parts per million that's the formula so the mass of the solute 0.125 divided by the solution 250 times 1 with 1 2 3 4 five 6 zeros don't mess that up okay so we get 0.125 / 2 50 equals * 1 1 2 3 4 5 6 equals all right 500 which one of these numbers is 500 well here is really the decimal point right one two I have to move it two places for it to look like this so that means there is my answer given the equation representing a nuclear reaction particle represented by X is okay so here's what's important here's the uh divider between the two sides of the equation the top numbers on this side must equal the top numbers on this side the bottom numbers on this side must equal the bottom numbers on this side so if this is five this also has to equal five so what has the bottom have to be yeah a four so these are wrong the top over here is 10 right so the top over here also has to be 10 so what does the top have to be nine okay well now I need to look at the periodic table and which one of these two has an atomic number that's the bottom number atomic number of four and it's going to be this one what is the vapor pressure of propanone at 4 45° C so you got to know how to read table H okay so 45 so 25 30 35 40 45 so that's right here go up until we hit propanone line right here go across and what is that vapor pressure that's it what is the number of electrons shared between two atoms in an O2 molecule so we need to know the number of electrons shared in bonds okay so oxygen looks like this so in a Le do structure it has six dots right so that means when I have another oxygen that's going to bond with it I have the same electron dot diagram so this electron will bond with this one and this electron will bond with this one so how many electrons are shared this many it will look like this 1 2 3 4 1 2 3 4 okay how many electrons are shared in a triple bond so six it would be three pairs right but six total electrons Which statement explains the low boiling point of hydrogen H2 at standard pressure so you have to know the relationship between intermolecular forces and boiling point so if it has strong intermolecular forces it has a high boiling point so if it has a low boiling point it has weak intermolecular forces so when you look at the chart at this table for this question which compound has the strongest intermolecular forces the highest boiling point all right which formula represents a saturated organic compound so we have to know saturated versus unsaturated this is the only one that's saturated because it has all single carbon carbon bonds these two are unsaturated because they either have a double or a triple bond so I need to find the formula that matches here's the easiest way look at how many carbons you have double it what's double two four do I have four hydrogens no I do not do I have more or less less so that's this one bad news okay how many carbons do I have two double two what do I get four do I have four hydrogens yes I do which means it's this one ah bad news again okay try this one how many carbons you have three double three what do you get six do I have six six hydrogens no more or less less oh no well I'm hoping this one is right okay I have three carbons Right double it do I is six right do I have six hydrogens no do I have more or less more which means finally finally I have something that fits that chemical formula that general formula which phrase describes the molecular polarity and distribution of charge in a molecule of carbon dioxide so we need to know how to determine if a molecule is polar so carbon dioxide looks like this this is one of those things that you just have to know this is its structure it's linear okay what else do you have to know the structure of uh ammonia like this okay uh methane like this those are all H's water like this right has some unpaired here this also has I mean paired here but unbonded okay um nitrogen just diatomic nitrogen like this uh diatomic oxygen which we did earlier just like this these are probably the most common ones okay but anyway this bond is polar because oxygen pulls harder so this side is partially negative but this is the exact same so this side is also partially negative as a result since it's equal Pole from both sides the molecule ends up being symmetrical which means it is nonar because it is symmetrical an atom of which element bonds with an atom of hydrogen to form the most polar bond so in this case we need to know how to use electro negativity to determine Bond type okay so in general the closer you are to zero the more nonpolar the you know kind of in between is going to be polar Po and the greater than 1.7 or big differences are going to be ionic so what I need to do is look up the electro negativity on table s for each of those elements and I'm comparing it to hydrogen so I'd be subtracting so for hydrogen and bromine I would do 2.2 minus I mean 3.0 minus 2.2 so I'd get 0.8 and I would do that for each one and where is the biggest difference that is most polar and so that will be Florine which statement describes the bonding in an Aline molecule so I need to know how to interpret table Q right so you can see that alkin have what kind of bond oh yeah a carbon carbon triple bond which formula represents two buttin so it ends in in right which means it has a double bond so eliminate eliminate it's two buttine so if I number the carbons like this one two 3 4 One Two 3 4 what's the lowest number that the bond is attached to one so that makes this one two ding ding ding is the right answer which compound has a functional group that contains two oxygen atoms so you need to know how to interpret table R so table R is big and looks overwhelmingly complicated but it absolutely is not overwhelmingly complicated in fact it gives you absolutely so much information okay so I'm going to just look straight here down functional groups and look for two oxygens right here and right here now look at the names either it's going to be something an noic acid or something like this oh yeah look is literally the one that was on the table okay given the F Formula representing a compound what is a chemical name for the compound so you can see I have this which is chloro but that doesn't help me you can see they're all chloro right but you can see that some of them end with in and some end with a so this has has all single bonds so that means it has to be aim right now which number is that chlorine attached to that functional group so if I number this way it's attached to four and if I number this way it's attached to two correct which one do I use the lowest the lowest number possible so in that case it's going to be this one which formula represents a hydrocarbon so you need to know what a hydrocarbon is it literally only contains carbon and hydrogen carbon and hydrogen okay these are on table q but again they're specifics about hydrocarbons which term identifies a type of intermolecular force so you need to know that hydrogen bonding is a strong type of intermolecular force it is between in particular hydrogen with one of three very electronegative elements n o and F hydrogen bonding given a formula which formula represents an isomer so you need to know the definition of isomers so isomers have the same molecular formula but different names and different structural formulas so if you look here I have one o when I look here I have one o in all of these I have three C's well I'll have three C's in all of these so I have three six 7 eight hydrogens correct so 1 2 3 4 5 6 nope 1 2 3 4 5 6 7 8 looks like could be this one 1 2 3 4 5 6 1 2 3 4 5 6 so there we go same molecular formula but different structural formulas which means they have different names so this one is an alcohol this one is what an ether based on table G what is the mass of KCl that must be dissolved in 200 g of water at 10° to make a saturated solution so I need to know how to interpret table G okay here's what also I have to notice so this first question has a bunch of things so it says in 100 G of water but my question has 200 so first let's answer this as if it were a 100 so at 10° C find kl's line right here right so in 100 gram of water I need 30 gam of KCl but I don't have 100 gram of water I have 200 right so what do I do okay well I could cross multiply or just realize this is doubled right so what do I do I double it okay based on table G which Sample When added to 100 gam of water oh thank goodness this time and thoroughly stirred produces a heterogeneous mixture all right so let's look so KCl it's line 20° C so for CASL either I have 20 G or 80 g so 20 G is right here and 80 g is up here so this point right here for 20 G is under casl's so it would be un saturated this point for 80 is way above the line so it would be super saturated all right let's look for KI ki's line is way up here right so at 20° C uh if I have 20 G right again here that is under that line but 80 grams is also under the line so which answer do you think it is yes obviously this one why because super saturated means that there's too much of it so it didn't all dissolve compared to the freezing point and boiling point of water at one atmosphere a 0.5 molar aquous solution of NAC at one atmosphere has all right we need to know how freezing point and boiling point change with the addition of a solute so if here is just a basic thermometer this is the boiling point of water and this is the freezing point of water when we add stuff to water the boiling point the high number goes higher when we add stuff to water the freezing point the low number goes lower and here's the thing the more we add the lower it goes the more we add the higher it goes so if we compare to what water's numbers are a solution must have lower freezing point and higher boiling if we're comparing for this one to a one molar solution a TW molar has more stuff so what happens the boiling point gets even higher and the freezing point gets even even lower what is the marity of 2 L of an aquous solution that contains 0.50 moles of potassium iodide or Ki so we need to know how to calculate marity which means we need to know how to use this formula so moles 0.5 L 2.0 so in our calculator we are going to do 0.50 / 2.0 and we see our answer right there we go how many milliliters of one molar HCL aquous must be diluted with water to make exactly 500 mL of a 0.1 molar HC CL aquous okay so we need to know for this one how to use the titration formula so that's right here in this question it's not actually asking for a titration but we calculate it exactly the same way this is showing what happens in a titration this is what we want as the equivalence point this is the end this means we added to much what we do is we add either acid or base this way we have the opposite one so let's say this is acid I would have base here plus an indicator as I'm adding the acid drop by drop I'm waiting until I see just this change so I'm like swirling and then I'm trying to get that exact super pale pink and that indicates uh neutralization okay okay yeah so in this case I don't really have marity of um acid and marar and volume of acid and marity of base and volume of Base but I can use this same formula so for marity I have 1 times I don't know what this volume is equals right the marity over here 0.1 time this volume okay so I just do1 * 500 = 50 and there we go there is our answer systems in nature tend to undergo changes toward well we need to know what energy and entropy changes are favor well the universe really doesn't like to exert a lot of energy so low energy and as a result cannot put things in order so low energy and high entropy entropy is Disorder so if we word the question like this systems in nature tend to undergo changes toward it's going to be low energy and greater disorder entropy is disorder or randomness based on table J which chemical equation represents a reaction with a heat of reaction that indicates a net release of energy so we have to know how to interpret table I oh I said table J by mistake but this is literally table I okay so a net release of energy you can see at the bottom it says a minus sign indicates exothermic so that is release right so what I'm going to do is look through for each one of these equations and find which one has a minus sign and that is going to be this one okay based on table I which see there I read it correctly this time which equation represents a reaction with the greatest difference between the potential energy of the products and the potential energy of the reactants so here it's seeing do you know that heat of reaction is literally that's what this is the definition of the difference between the potential energy of the products and the potential energy of the reactants is literally heat of reaction okay so which one has the greatest so you just find each one so we have this one that's the first one and then we have this one right here right and then you have which one up here Yep this one and then we have this one right so which one has the greatest there we go given the potential energy diagram representing a reaction which numbered interval represents heat of reaction let's go through what they are this shows potential energy of the reactants this shows potential energy of the products this sorry for the Crooked Arrow would be two and three together that shows the activation energy of the forward reaction okay three shows the activation energy but for the reverse reaction so going starting here and ending here okay two is products minus reactants this represents Delta H or the heat of reaction okay it ties to table I right those are Heats of reaction but it is going to be number two solution a has a pH value of 2.0 and solution B has a pH value of 4.0 how many times greater is the hydronium ion concentration in solution a then the hydronium ion concentration in solution B well we need to know how a one number change in PH affects hydronium ion concentration so if our pH scale goes from zero to 14 right with seven being neutral the most H+ is hydrogen ions or h3o Plus's hydronium ions are over here here the most o negatives are over here so if hydronium is increasing I move this way okay so how many times greater is the hydronium ion concentration so we have a pH of two and then we have a pH of four okay so how much greater is solution so this was a and this is B right so here the concentration changes time 10 and here the concentration changes time 10 and 10 * 10 is what 100 when the concentration of hydrogen ions in a solution is decreased by a factor of 10 first of all how many numbers does it move on the pH by one so I know know those are wrong the hydrogen ions are decreasing that means I'm moving this way right so the number yeah increases by one which statement describes the changes in bonding and energy that occur when a molecule of iodine I2 forms two separate atoms of iodine well what do you have to know that you have to know what happens to energy when bonds formed or are broken so when bonds are broken we have to put energy in so in this case I'm breaking the bonds because I'm going I2 into I + I so I'm breaking bonds when we break bonds we literally have to absorb energy this one says when an atom of chlorine atom of hydrogen and an atom of chlorine combined to form a molecule of hydrogen chloride what happens a bond is formed the opposite happens so energy is released an indicator is added to an aquous solution with a pH value of 5.6 which indicator is paired with its observed color in this solution so you need to know how to interpret table M okay in table M if it is if the pH is below this number it will be this color if it is above this number it will be this color so at a pH of 5.6 what color will methyl orange be absolutely yellow but let's check the others pheno thaline at 5.6 colorless Bram crease all green at 5.6 blue thol blue at 5.6 yellow okay what is the color of Bram crol Green in an indicator in a solution with a pH value of 2.0 Bram crol green when it's 2.0 will be what yellow which form of energy is converted to thermal energy when propane Burns in air so you need to know how to recognize types of energy and something really important is that uh temperature is not energy but also the kind of energy stored in bonds is chemical which form of energy is transferred when an ice cube at 0° C is placed in a beaker of water at 50° C first the energy would transfer this way right from warmer to colder but the kind of energy that's moving L thir which particles are transferred during a redo reaction well it's literally Leo says yeah you have to know what happens when Redux electrons given the equation representing a reaction during this reaction each element changes in oxidation number identifying Redux where we have elements with zero oxidation state than elements without zero oxidation States in an electrochemical cell oxidation occurs at the you need to know which reactions occur at the anode and the cathode so an ox red cat so oxidation at the anode When comparing voltaic cells to electrolytic cells oxidation occurs at the literally anox not a special situation of anox always anox so anode always oxidation all right which energy conversion occurs in an operating electrolytic cell well what happens is we need to know about spontaneity and energy conversions in electrochemical cells in electrolytic it is electrical to chemical in voltaic it is chemical to electrical electrolytic must contain a battery so it is forced that means it is not spontaneous voltaic is literally a battery so it is spontaneous So based on table atoms of which metal will lose electrons to C A + 2 ions first of all find calcium here on this table okay um which metal will lose electrons well it's going to be above I don't even have to remember that watch where's aluminum here where's lead here where's nickel here here where's potassium hm I wonder what the answer is yeah it's the one that's different right the one that's above it based on table J which metal is more active than tin okay so let's just switch colors to make this less confusing so here's 10 uh let's find them we have a c r CS and MN so it has to be more active than tin but less active than zinc so which one is between them yeah there we go all right which phrase describes the direction of electron flow in this cell so you can see that it's voltaic it tells you it's voltaic right so um what we should know is that uh table J matters right and we have to know how to interpret these diagrams so here's table J and we have magnesium and we have nickel so let's write down everything we could write down about them the more active metal is negative this one will be positive since it's voltaic the the higher metal will be the anode and the uh lower metal then will be the cathode this is Leo so that means oxidations occurring here reduction or um red for well that didn't help you was the G part right so um Leo says G right G is reduction and red hat reminds you that reduction at the cathode okay that can help you here or G and then an ox right so at the anode is oxidation um and then we have fat hat so what I'm going to write it up here what fat that Pat tells you is that electrons go from anode to cathode Through the Wire okay also the cathode gets fat so this Mass goes up and this Mass goes down as the cell operates okay so direction of electron flow it does not go through the salt bridge what goes through the salt bridge ions in both directions to keep the cell neutral So It Goes Through the Wire from anode to cathode so what is that from mg Through the Wire to ni which half reaction equation represents reduction okay well you need to know how to identify oxidation verse versus reduction so remember Leo says G right uh here a quick number line 0 1 -1 moving this way I gain electrons I get more negative moving this way I lose electrons I get more positive why does that matter see the direction of the arrow it points to the side of the equation where I must have the electrons so if it's asking about reduction the arrow points this way the electrons have to be on the reactant side so wrong and wrong right now to determine which one is correct I need to see which one has charge balanced so this is the only one because this is a plus two right and this is a minus two that equals zero okay now what about this one okay oxidation okay so again it points this side right which means the the electrons need to be on that side so this one's wrong and this one's wrong and which one shows balance of charge uh okay well they both do right now no they don't plus 2 and min-2 does equal 0 + 2 and -2 equals 0 not positive 4 silly me okay right there given the equation representing a reaction the oxidation number for of copper changes from what to what okay so we need to know how to determine oxidation number so here are all the elements here so you can see here copper is alone it's a zero here aluminum is alone it's a zero so copper ends with a zero right cuz here is the uh product side now what did copper start as well here it's combined with chlorine chlorine has a NE one but there are two of them so that was where the Cs so if there's only one copper what did it have to be yes all right now when we look at the next one here's where table e comes into play says what are the two oxidation states of nitrogen now I can't solve for two variables in one thing so I'm going to use table e and what I'm going to do is find nh4 and see that it is + one and NO2 and I see that it is minus1 right so those are the oxidation States uh options for nitrogen hydrogen oxygen let's do oxygen first cuz I think that'll be more helpful okay so I have two oxygens but each one is -2 so that's -4 but the whole thing equals -1 it doesn't equal zero so what does the nitrogen have to be yeah so positive3 right well look okay so a positive three here positive three it doesn't say they have to be in a certain order but I can eliminate this one right okay let's try the other one so nitrogen with hydrogen now it has two now here's a weird thing because hydrogen is always positive one unless it unless it's with a metal is nitrogen a metal no so that means hydrogen is + one but there are four of them right so + one + 1 + 1 + one so it's +4 right and it equals a total of posi one so what does this nitrogen have to be yeah it has to be minus three so in this case solving them separately you did just have to remember a weird thing right that hydrogen is only the negative one if it's combined with a metal and then in that chemical formula it would be listed second so it would be like Li I as an example okay I yeah to know how to balance equations okay this was a little bit of a harder one that was on uh the exam last year um harder than it normally is um why do I say that first of all there was oxygen in two places on this side and um normally you can kind of give yourself a head start by putting a two right um but when I do that so let's just say if I put a two here that means I would have two n's right and six H's right and then if I try to fix the six hes I would put a three in front of here so if I put a two right I would get this putting a three right means I have six hes beautiful but then I have three o why is that problematic because three is an odd number like you can't get it to work so you're like oh well that's easy I could just put a three here right and that would be uh you know make it wor work out except for I don't have three nitrogens over here GH so I don't like it so this looks like a mess so what I'm going to do is just say I'm going to double this because I really don't want an odd number of oxygens so I'm just going to guess and say six okay so that gives me 6 * 2 is 12 hydrogens so how would I make there be 12 hydrogens do this right that makes me have four nitrogens so make there be four nitrogens so can I make it work four * 1 is four oxygens 6 * 1 is 6 oxygens that's 10 so I would put a five here so the ratio of the coefficients is four to 5 to 4 to 6 and no I cannot reduce cuz there's an odd number in there okay literally I hated it but that is is um that is what it equaled not my favorite uh it's very unusual for there to be one so difficult okay and then uh the last question that we're going to go over here well given the formula of a compound what is the molecular formula so you have to know how to find molecular formula or what it is and literally just count them up add them up real simple okay so we end on a really easy peasy note now there's obviously a lot more to know for this exam but this gives you a great sampling of questions that literally show up over and over and over and over again good luck ask questions if you have them