hey everybody welcome to chapter six we're going to be going through the opening five sections uh we're going to return to chapter six a little later in the course just to wrap it up uh but let's go ahead and jump in so we're going to be spending some time doing some chemical calculations today uh let's start by thinking of our sodium intake so when we intake sodium we're not taking in the sodium metal that we talked about in previous chapters remember we talked about sodium metal being a little soft almost bread like to where you could cut it but it was still metal it was still shiny but it was incredibly reactive when we take in sodium in our diet typically we're looking at an ionic compound like nacl so nacl is not entirely sodium nacl is also chlorine so we've got chloride ion and we've got sodium ion so when we take in table salt we're not just taking in sodium well sodium ion is really key to the body it helps regulate your fluids and it helps to regulate blood pressure too much sodium trends with high blood pressure so the fda has a recommended daily allowance of under 2300 to 2400 milligrams per day so one of our goals today is to look at this salt shaker here and try to determine what portion of that is actually the sodium that we're taking in so that's how we're going to wrap up the lecture but we're going to build our way there but the theme of today is looking at very tiny things in a practical way and looking at a ratio of parts to the whole so let's start at looking at that ratio of parts to the whole let's start with this question of these red rock formations i did a conference in arizona one time and they had these beautiful red rock formations now it's beautiful when you see it here when you're in north carolina and your grill's sitting outside in the backyard and you see that reddish tint start to develop on the black grill that's a problem because we're looking at rust and that is the oxidation of iron it's the reaction of iron with the air that's surrounding it and you're actually looking at iron oxides that are present in the red rock formations here so a good question we could ask is how much iron is present in a given amount of iron ore or the rock that's present in these formations we would have to look at the ratio of the parts to the whole so if we looked at iron iii oxide here fe2o3 we would want to look specifically at how much iron there was relative to the entire compound another way we can look at this if you've heard of cfcs chlorofluorocarbons we could take a moment and look at the now outdated chlorofluorocarbon freon12 and we could look at how much chlorine or how much fluorine for that matter is present in this compound so the compound is shown down here in a structural formula notice how it's got two cls that's the part that we're interested in relative to the entire molecule so we're going to spend today looking at isolating just one part of the whole and looking at very tiny atoms very tiny molecules and making them practical to work with in calculations so let's start off by thinking of doing a little home improvement so think about lows think about ace hardware or home depot they don't sell really individual nails that's not what they're all about it's not really practical to count these little pieces of hardware on a one by one basis so what you tend to see if you go into buy nails is you'll buy pounds of nails so instead of buying a 25 pack of nails you tend to see it listed by the pound and that's because practically speaking these are very small and it would be difficult to count out if say you wanted to purchase a thousand pack of nails or 782 nails instead you're purchasing say five pounds 10 pounds or 15 pounds of nails it makes it practical so same idea in chemistry we don't measure out atoms and materials by counting our atoms or by counting our molecules instead we use balance and we use that balance to measure mass so if you see on the scale here we measured out 8.25 grams a measure of mass of carbon instead of trying to count out the individual molecules or individual atoms that were present it's very impractical to do that so instead we take an easier route of working with the practical unit of mass or later we're going to learn about the unit of moles so why don't we count them out when i say that it's impractical to count out our single atoms or single molecules i really mean it's impractical they are tiny seriously tiny in fathom and fathomably small so picture a piece of iron so i've got it over here and it weighs roughly the same as this m m so about 1.13 grams so m ms aren't very big this piece of iron would be even slightly smaller if we tried to count all of the atoms that were present in this tiny little iron bowl it would take us 386 billion millennia now a millennia is 1 000 years would take 386 billion millennia let that sink in for a minute and that's where we're counting one atom per second and we're really really good at what we're doing and don't have to start over halfway through now how do we make this more practical we take the hardware approach we start to think on ways we can group these very tiny particles efficiently so let's do a sample problem where we look at purchasing nails but we're purchasing them by the pound and we're going to convert to the individual nails that we purchased so let's read the problem a customer buys 2.6 pounds of medium-sized nails so that's some given information that's something we have so we have pounds of nails and we have 2.6 pounds now a dozen of these nails weighs 0.150 pounds okay this right here looks like a conversion factor to me and the reason it does is because it relates dozens to pounds so let's start looking at our solution map if i want to go between pounds and dozens they gave me the value 0.15 pounds per dozen so if i start in pounds and i want those to cancel then i'm going to say one dozen divided by 0.150 pounds and i would want to put my pounds on the bottom that way it cancels out with what i start with and then i'll be a dozen nails and i want to go to number of nails because the problem asks me how many nails not how many dozen nails so we'll need to go that one extra step to say for every one dozen of really anything i've got in this case 12 nails and it's set up the way it is with dozen on the bottom so a dozen will cancel out and leave us with individual nails so let's start with what we're given 2.6 pounds of nails we're going to use our first conversion factor to get to dozen nails so i'm going to put 0.15 pounds for every one dozen and then i'm going to use my second conversion factor to go from dozen nails to individual nails so here i want dozen on opposite sides so for every one dozen nails i'm going to have 12 nails so let's see if it all cancels out right pounds started off on top i put pounds on the bottom so they cancel dozen was on top cancels with dozen on the bottom and we're left with the unit nails we would take 2.6 times 1 times 12 and then we would divide by 0.150 and divide by 1. so we would end up with 208 nails that this customer purchased now that's a reasonable value based on the conversion factors that we were given so let's move on here now we said that the atom was super small and we need an efficient way to count these super tiny particles so if we're looking at something like an egg an egg you can hold in the palm of your hand not that tiny but still we count those in terms of dozens because it makes it practical to count now we need to have the same idea we need to have the idea of a dozen where we can group a large number of atoms into something that's practical to talk about and practical to use for calculations so the chemist doesn't is called the mole the unit i know it's a great abbreviation doesn't make a whole lot of sense we drop the e off so the unit is mol i know that shortened it quite a bit now if we were looking at iron atoms element fe on the periodic table one mole of iron atoms is 6.022 times 10 to the 23rd iron atoms one mole of rice grains is 6.022 times 10 to the 23rd rice grains if you notice this number is the same in the same way i could have a dozen bowling balls or a dozen frisbees a dozen means 12. in the same way if i have a mole a mole means 6.022 times 10 to the 23rd items it could be rice grains it could be atoms now this is called avogadro's number we will see this popping up throughout the course it's kind of like pie in a geometry class in the sense that it's going to be useful to know off the top of your head and if you're doing enough practice problems it's not something you're going to have to force yourself to memorize it's going to be something that you dream about or you might mumble in your sleep okay now the mole is practical for describing things that are unfathomably tiny so if i'm talking about iron atoms one mole of iron atoms weighs about .12 pounds one mole of rice grains weighs 2.8 times 10 to the 19 pounds so that is a huge weight so even going the scale of rice grains the mole becomes quickly impractical so we're talking about a unit the mole that's only practical on the very tiniest of scales so your big two take home ideas so far is that these moles represent a huge number of items that number was 6.022 times 10 to the 23rd items now the mole does not represent a mass it represents a counted number of items avogadro's number fourth moles of different substances weigh different amounts that's your second big take-home if i have a mole of iron we said it weighed 0.12 pounds a mole of iron atoms tiny little iron atoms you go a little bigger mole rice grains weighs a huge number of pounds are they both the same number of items yes but do they weigh the same absolutely not okay so he said that the mole makes the atomic scale practical it makes it easy to handle or easy to picture two large helium balloons that you might get at harris teeter oh i was going to make an inflation joke here but too soon one mole of helium atoms is about two large balloons so the helium gas the number of helium atoms that are contained in these two balloons is roughly one mole if we look at solid copper we're assuming that these are solid copper all the way through pennies about one mole of copper atoms would be about 22 pennies so the mold does its job of making something that's too small to see practical to hold in your hand okay so we need to be able to move and this is the goal for the next few minutes between the idea of moles and mass and molecules or atoms so that's what we're going to be focusing on for the next little bit is working through the word problems working through the language to make sure that we can use this concept called the mole because in upcoming chapters it's going to be a big deal okay so we've got a a problem listed here and it wants us to take three and a half moles of helium to the number of helium atoms so i want to go from moles which is what i have to helium atoms which is what i want if we look at the solution map here and i need a conversion factor we can just use one to make that jump between moles and atoms now we said that avogadro's number was 6.022 times 10 to the 23rd and that represented the number of items per mole well if i have one mole of helium then that's going to be avogadro's number's worth of helium atoms if we set it up with moles on the bottom we can cancel what we started with and end in atoms so let's try this out we're going to start with our 3.5 moles of helium we're going to add in that first conversion factor and for every one mole of helium we've got 6.022 times 10 to the 23rd helium atoms moles cancel just as planned leaves me with atoms and then we're going to take three and a half times avogadro's number and divide by one and we get an answer of 2.1 times 10 to the 24th helium atoms for our final answer okay big thing here make sure you can use scientific notation in your calculator before the next exam hits contact the ilc come see me during office hours find a way to make it work because scientific notation and calculator use is not going away okay so next problem so in our previous one we went from moles to number of atoms now in this problem we're going to go the opposite direction we're going to go from what we have which is silver atoms to what we want which is moles of silver okay so the problem gives me 1.1 times 10 to the 22nd silver atoms now silver ag on the periodic table and we need to use one conversion factor to move between atoms and moles and we said last time that that was avogadro's number so i'm just going to make a little note to myself here i'm going to use avogadro's number for my conversion factor so let's decide how we're going to orient that conversion factor to make sure that everything cancels out properly we're going to start with what we have 1.1 times 10 to the 22nd and this is silver or ag atoms i want to end in moles so i'm going to not cancel moles but leave it behind here i want atoms on the bottom because i need them to cancel and we know that for every one mole and this is just our definition just like one dozen is 12 items for one mole we're going to have 6.022 times 10 to the 23rd atoms so this time we're going to take what we started with the 1.1 times 10 to the 22nd silver atoms we're going to divide by avogadro's number to get our final answer and that works out to 0.018 and that is moles of silver so i want to point out something important here and this is something that may have been lost on the first exam so let's look at that first problem that we worked in the first problem whoops in the first problem we put avogadro's number on top in the second problem we put avogadro's number in the bottom now the rule is opposite sides cancel not whatever you want to cancel just goes automatically in the bottom so in the first problem i was trying to cancel moles so i put moles on the opposite side moles on top moles on bottom cancel and the second problem i was trying to cancel atoms so i put avogadro's number worth of atoms in the bottom so atoms would cancel so you have to be careful how you use avogadro's number as a conversion factor to make sure your units cancel out properly okay our next big jump is to head over to the periodic table and we're going to interpret this number that we spent a little time with toward the end of our last exam's material this was our average atomic mass and we're going to be able to take that and use it even more widely so so far the way we've looked at this 12.011 is the mass of a single carbon atom so about 12.011 amu's atomic mass units of carbon for every one atom but now we can think bigger this is going to apply to the mole also so we can use that same value we can use 12.011 but we can think of it as the number of grams of carbon for every one mole of carbon and then every mole doesn't matter what it to mole of is going to be avogadro's number worth of uh atoms or molecules or items so here we get this really important relationship i'm going to box it here super key right off the periodic table i've got 12.011 grams of carbon i know that's the mass of a mole of carbon and i know that's avogadro's number worth of carbon atoms so there's a lot packed into this number right below the element symbol on the periodic table now one that's going to follow us is this idea of grams per mole so this 12.011 is the number of grams of carbon per mole of carbon and see this is a relationship between grams and moles this is going to prove to be a useful conversion factor from here on out molar mass is going to be a common term that we use being grams per mole and that relates the number of grams per mole of the substance same number but we change the unit and we're talking about atomic mass units we're talking about the molecular mass the mass of just one molecule one atom on the atomic scale rather than our molar scale okay so that was big take home idea number one big take home idea number two did we change this number when we were looking at the mass of an individual carbon atom versus the mass of a mole of carbon atoms no all we changed was the unit so when we think on the molecular or atomic scale i'm working here when i think on the molar scale i'm thinking in terms of grams per mole okay so let's use this idea remember this relationship right here and carbon specifically again one mole of carbon if i want to know the mass of one mole of carbon it's going to be the value right under the element symbol here the average atomic mass we express that in grams per mole similarly if i was looking at oxygen oxygen has the number 15.999 underneath it on the table so where one mole of carbon weighs 12.01 one mole of oxygen would weigh 15.999 with a unit of number of grams packed into one mole of oxygen now so far we've just been looking at these individual atoms let's start to think about compounds so if i start to look at a compound like co2 then i'm looking at one mole not just of carbon atoms but one mole of carbon dioxide molecules so if we broke that up that would be one times one that would be one mole of carbon and one times two that would be two moles of oxygen now we can get the mass per mole of carbon and oxygen off the periodic table we know that this 12.011 value is the mass of one mole of c and this 15.999 is the mass of one mole of oxygen so we can figure out the mass of one mole of carbon dioxide it would be one times this 12.011 plus i would have two because i have two moles of oxygen that show up in this formula times our 15.999 grams per mole for oxygen and we would add this up so this would equal 44.009 and our unit would be the number of grams of co2 that show up in every mole of co2 so we would call this our molar mass for the compound carbon dioxide now let's use this concept of a molar mass to move between grams and moles sample problem here asks us to calculate the number of moles of carbon present and point flat .58 grams of diamond so for diamond we're looking at carbon and for carbon we've got 12.011 grams per mole specifically grams of carbon for every mole so we're going to use that as a conversion factor so what we have is 0.58 grams of carbon and what we want and i apologize for that noise in the background i think they're working uh downstairs on uh the electrical work okay we want moles of carbon to get that done i need a unit in grams per mole to help me move between these two units so our conversion factor is going to put grams on the bottom so they'll be able to cancel i'm going to put moles in the top here so i'm going to be able to keep that unit a mole from the periodic table it's 12.011 grams for every one mole so i'm going to start out with what i have 0.58 grams of carbon i'm going to use that first conversion factor that's going to help me move between grams and moles like we said 12.011 grams grams go opposite from grams that were on the top originally so they cancel for every one mole so we get 0.58 divided by 12.011 and that is going to give us 0.048 moles of carbon so we want to look at the similarity here where we were looking at nails and making it practical to sell and practical to think about and atoms where with them being so tiny we had to figure out a way to calculate and work with them so let's start off by thinking of nails we started off by selling nails in terms of weight we'd use the conversion factor knowing the number of dozen nails per pound and that would get us to a grouped number of nails so then we would use the number of nails in that group one dozen nails was 12 nails and that would get us to individual nails and we said that hardware stores did this because it was more practical to weigh out what they're selling instead of weighing out the tiny individual nail now when we think in terms of atoms we go by mass which we can get from a balance in the lab we don't count out the individual atoms or individual molecules that we're reacting because they're impractically small and then we can think of these in terms of a group so we have a grouped number and that was our mole so for nails we were thinking in dozen for atoms and molecules we think in terms of moles and then we can take those moles and finally end up in terms of individual atoms and we did that by having a relationship between moles and our individual item or individual atom and that was avogadro's number remember that is a super key constant really you have it worth having on the back your head ready to use in any moment okay so let's go another step we want to go from what we have here what we have is mass and we want to go to atoms so how many aluminum atoms what we want are in an aluminum can with a mass of 16.2 grams well here i've got aluminum off the periodic table so our value at the bottom there means that we have 26.982 grams of aluminum per mole and that's going to help us move between grams and moles so if what i have is grams of aluminum i have 16.2 grams then to get to moles of aluminum i'm going to have to use this value off the table i have grams starting on the top so i'm going to have to put grams on the bottom so i would use for every one mole oops i'm going to have 26.982 grams of aluminum and that first conversion takes me over to moles now my end goal what i want is to end in the number of aluminum atoms so i needed that way to jump between moles and individual atoms and that was avogadro's number now let's put all this together if we start with 16.2 grams of aluminum we use that first conversion factor from the periodic table and we have 26.982 we're putting the grams on the bottom so they cancel with the grams that started on top for every one mole of aluminum and then our second conversion takes us home from moles to number of aluminum atoms and here moles on top so i'm going to put moles on bottom and up top i would put avogadro's number so 6.022 times 10 to the 23rd and this is aluminum atoms so in your calculator we would take 16.2 and multiply by what's on the top so multiply by avogadro's number divide by what's in the bottom so i divide by 26.98 we're left with a unit of atoms which is what we wanted and we get 3.62 times 10 to the 23rd and this is aluminum atoms okay so we're stepping up in difficulty but the approach stays the same same as we did in chapter 2 when we do conversions we want to align the conversion factors top and bottom so units cancel if we ever have to go between grams and moles and this has been every conversion problem we've done so far today moving between grams and moles i use the molar mass moving between moles and atoms i've been using avogadro's number so feel free to pause this one try it on your own even if you're not sure it helps to struggle a little bit because nobody was born knowing this and uh it helps you learn the process a little better than watching it all the way through so go ahead and pause the video read through try the problem and we'll get going in a few minutes okay i'm trusting that you paused it and tried it on your own if you didn't try it next time or go back and try it after you've watched the entire lecture bottom line practice is key so sample problem calculate the mass and grams of 1.75 moles of water so what we want is mass what we have is moles and we're dealing with not just an element but we're dealing with a compound because water is h2o and h2o is bonded together it's got two or more elements in it so it's going to require us to think of more than one element when we're doing this calculation so i need the molar mass not just of hydrogen not just of oxygen but of this formula just like we calculated it for co2 earlier here i've got two hydrogens so i'm going to take two times the mass of hydrogen here 1.0078 and then i'm going to take 1 times 15.99 and when i add that up i'm going to have the map the molar mass of h2 oh okay so let's see what we get so we get 18.0146 let's make ourselves a little note and that is the number of grams of h2o for every one mole so when i come over here moles of h2o it tells me that i have 1.75 moles to start with and it tells me that i want grams of h2o so i'm trying to go from grams and moles so i need that molar mass which we just calculated and i start with moles on top so when i use this i'm going to put moles on the bottom so i'm going to have 18.0146 grams with moles on the bottom so it cancels now something important here i want you to be careful on these molar masses molar masses are always in terms of one mole it's just like saying 12 eggs per one dozen it's not 12 eggs per two dozen this is a definition so for every one mole we get avogadro's number worth of items for every one mole we get the molar mass that we added up off the periodic table so let's write out the calculation 1.75 moles of h2o and we know that for every 1 mole of h2o we're going to end up with our 18.0146 grams so i take the number they gave me 1.75 multiplied by the molar mass of water and i get my final answer and i end up with 31.53 grams of h2o which is good i ended up with a mass which that's what i was trying to end with grams of water so let's uh let's go another step further here it wants the mass so we're aiming for grams but it's giving me molecules so let's toss an extra little twist in here so i'm going to make note of that we have 4.78 times 10 to the 24th these are no2 molecules ran out of space here so i'm just going to write it below it and eventually i want grams so i want mass and let's see if we can work our way through this i need a way to relate molecules with moles so i'm going to use avogadro's number there's 6.022 times 10 to the 23rd no2 molecules for every 1 mole of no2 to go between moles and grams i need a unit that's grams per mole and that's our molar mass and we're going to have to calculate that for no2 i'm going to take since it's no2 remember if i don't see a number it's just one of them so i have one nitrogen two oxygens so i'm going to take one times 14.007 i'm gonna add that to 2 because it's no2 i have 2 oxygens times 15.999 and let's see what we get i get a molar mass of 46.005 grams per mole let's go ahead and start plugging everything in and make sure that we have everything oriented correctly on top and bottom so i'm going to start with my 4.78 times 10 to the 24th no2 molecules and i'm going to use that first conversion factor to go from molecules to moles now i want molecules to cancel so i'm going to put them on the bottom i want moles to be that halfway step to my answer so i don't want to cancel it just yet and for every one mole i've got avogadro's number 6.022 times 10 to the 23rd okay so that gets me halfway there this is that first conversion factor my second conversion factor is going to be my molar mass so here i want to cancel out moles so i'm going to put them on the opposite side top and bottom and a molar mass relates moles to grams and we determined it was 46.00 grams for every one mole so moles canceled left me with grams which is what i wanted we're going to take this value we started with we're going to divide by avogadro's number and we're going to multiply by the molar mass to get our final answer and we get a final answer of about 365 grams of no2 so we said at the start we were thinking in terms of a ratio of parts to the whole so let's jump into that only let's look at clover leaves if i look at a three leaf clover then the ratio of the parts to the whole would be three leaves for every one clover so if i was trying to move between clovers and leaves then if i want to know how many leaves are on 14 clovers this would be what i have leaves are what i want and i would use the ratio of one clover for three leaves but i want to put clovers on the bottom and that is because i want it to cancel i have leaves that are left on the top uncanceled and that's good because that's the unit that i want to finish with so to figure this out i would take 14 times 3 divided by 1. so that's going to give me what that would be 42 leaves so yeah this is very similar to the math that we've been doing the entire day and now we're really focusing on parts to the whole so let's think about instead of the relief clovers let's think about carbon dioxide so this is a compound it contains two different elements so the whole would be co2 the part would be either carbon or oxygen that make up the hole when i look at this as a ball and stick model i've got my carbon in the center i've got my oxygens on the outsides i've got a ratio of two of these oxygens for every one carbon that i've got so if i want to look at the ratio of just this one molecule then i would say for every one molecule of co2 that i have got one c atom and i've got two oxygen atoms i could also look at total atoms for every one molecule i've got three total atoms so just like the clover we can break down this idea of the molecule now let's instead of thinking of an individual molecule of co2 let's think about one mole of co2 just like a teddy graham one of the little bear cookies for every one cookie you can break off two ears then we could say for every one mole of co2 we could say that one mole of c was present because this multiplies through one times one we could also say that i've got one times two i've got two moles of oxygen or when you put that together i've got three moles total of atoms so we could think of it in terms of an individual molecule and we still look at one c atom for every molecule or two o atoms for every molecule or three atoms total for every molecule or we could think in i mean much bigger scale and say for every mole of carbon dioxide it's a one-to-one ratio i have one mole of carbon i'd have two moles of oxygen in there or three moles of atoms total so these ratios are working on the molecular the atomic scale but they're also working on the much larger mole scale but they all come from the same chemical formula so here next problem it wants us to find the number of moles so that's what we want we want moles not just moles but moles of oxygen and this is our part in 1.7 moles so this is what we have of caco3 and this is the whole so calcium carbonate is the entire formula but we are just interested in the oxygen that's what we're aiming for so let's get this down in our solution map what i want are moles of oxygen what i have are moles of calcium carbonate calcium carbonate was our whole oxygen is the part that we're interested in now i have 1.7 moles of calcium carbonate and i'm interested in the moles of just oxygen that are present so i need to have a way to relate this so let's look at the formula for every one mole of calcium carbonate remember it multiplies through we're not interested in the calcium or the carbon we're interested in the oxygen so for every one mole of calcium carbonate i've got one times three three moles of oxygen so there is a one hole to three parts ratio a one to three ratio so let's try to work that in and use this as our conversion factor this 1 to 3 ratio so 1.7 moles of calcium carbonate and we would say that for every one mole of the whole there are three moles of just the oxygen that we're interested in so 1.7 times 3 we're left with moles of oxygen and we end up with 5.1 moles of oxygen or three times as much because of this one to three ratio so where we started this lecture was thinking about sodium chloride table salt and we started talking about sodium intake and how if we consume table salt we're not just consuming our sodium we're also consuming chloride so let's figure out just our sodium not the mass of the table salt but the mass of just the sodium so i'm going to start with 5 grams of nacl so this is what i have and it's a mass of the whole and where i want to end is also a mass but it's just a mass of the part it's the sodium that's in the sodium chloride so this grams of nacl i have five grams and i need to move between grams and moles whenever i need to move grams to moles i'm going to use the molar mass then i can get off the periodic table for that reason i've included this up top we'll get there in a moment to move between moles and moles this is going to be the ratio of parts to whole and then our last step here is to go from moles of sodium to grams of sodium so wait a minute i'm moving between moles and grams again so i'm going to need the molar mass but we have to be specific here so here i'm going moles of sodium to grams of sodium so i just need the molar mass of sodium over here i'm going grams of sodium chloride to moles of sodium chloride so i need the molar mass of sodium chloride so let's start this out knowing that we're going to have to do three conversion factors to get us to our answer and this is by the way the hardest of the problems we're covering today but it all uses the same principles and remember you can go back and try these out on your own also so let's start by adding up the molar mass of sodium chloride in the formula nacl i've got one of my sodium so i'm going to take 1 times 22.990 i'm going to add that to one of the chlorides because 1 shows up in the formula so 1 times 35.453 so i get that molar mass of 58 whoops let me get my pin back here get a molar mass of 58.443 grams per mole now over here for moles of sodium to grams of sodium we said we just needed that molar mass for sodium which i can just take the value straight off the table of 22.990 grams per mole our ratio of the parts to the whole we're looking at nacl to na and this formula has one sodium and one chloride for every nacl so my ratio that i'm interested in is taking from me from nacl to na so for every one nacl i'm going to have one n a that's the ratio that i want because it takes me from where i'm starting to where i'm finishing okay so let's write all this out we're going to start with 5 grams of nacl we're going to use our first conversion factor which is going to take us from grams of nacl to moles of an acl so i'm going to put grams on the bottom opposite sides cancel for every one mole there are 58 58.443 grams next i'm going to use my second conversion factor and for this and let me clarify a little bit i want to put one extra piece in here this is really about accurate labeling when we want to make sure that things cancel out properly this first conversion factor was 58.443 grams for one mole of nacl so then my second conversion factor would say for one mole of nacl i would get one mole of n a because we're just interested in the sodium so my third conversion factor takes me from moles of sodium to grams of sodium and we would say for every one mole of n a i get 22.990 grams moles of sodium cancel that leaves me with the unit of grams of sodium which that's what we were aiming for so we're going to the ones really don't count here in terms of when you enter it into the calculator 5 times 22.99 because it's in the top divided by 58.443 because it's in the bottom and that'll give us our final answer and that gives us our final answer of 1.97 grams of n a so to put this into perspective this is about the mass of four and a half m m's of salt so straight out of your your salt shaker this is about four and a half m m's that you can hold in the palm of your hand only part of that is sodium your recommended daily intake of sodium we said was about 2400 milligrams so this 1.97 grams of sodium that shows up in that 5 grams of sodium chloride that is about your daily recommended intake so about four and a half to five m ms and you've hit an equivalent mass of table salts that would have your daily value of sodium most americans we way overshoot so remember today was all about chemical calculations it was all about being able to calculate on the very small scale and the very big scale being able to convert between grams mass moles molecules and atoms and at the very end here we focused on parts to the whole calculation being able to calculate how much was present of just one portion of a more complex molecular compound alright so thanks for watching and stay tuned for our next chapters video