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Molar Mass and Moles

In chemistry, molar mass or molar mass constant, symbol "M", is a physical property that is the mass of a substance in grams divided by the amount of substance in moles. The base unit in the International System of Units (SI) for molar mass is the kilogram, which is almost exactly equal to the mass of a mole of water.

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Video Transcript

So in the previous video, we calculated the molecular weight based on the atomic mass units of each atoms in the molecule on DSO. In this video, we'll be talking about how to calculate the molar mass of a molecule and given the number of grams, we can figure out the number of bowls. Um and so the molar mass of a molecule is calculated in a very similar way to the molecular weight. Specifically, we can still use the same values on the periodic table for each item. So, for example, for hydrogen, it is one atomic mass unit. But it is also 1 g Permal and likewise for something like oxygen. Um, it's atomic. Fascinated is 16.0 and it is also 16.0 g per mole. And so the difference between the molecular weight and the molar mass is that molecular weight is in atomic mass units and Mueller Mass is in grams per mole. And so we usually use fuller masses. Um, when trying to understand the information that we get from chemical reactions one, so today, while we going over the commission of share like we've done before, and I'll show you, um, the different information that we can get just given grams for a particular molecule. Eso again, Let's write out the combustion of sugar. So sugar has a chemical formula of C 12, H 20 to 11, and in combustion reactions, the fuel will react thio oxygen gas to create some number of carbon dioxide molecules, as well as a number of war molecules. And again, When you're running chemical reactions, you want to make sure that your reaction is balanced. So it's a balance. This we'll need 12 oxygen molecules, 12 carbon dioxide molecules and 11 warm of molecules. And so, before we want Thio, figure out the number of moles. We have to be given a mass first, which I will give it later. But let's try to figure out the Mueller mass of each molecule to start with. So for carbon, um, this would be 12.1 g per mole for hydrogen. This would be one point 00 8 g Permal, and for oxygen, this would be 16.0 g per mole. So, yeah, I'm using the same method as before. We can calculate the Mueller masses of each molecule in this equation. Eso In the case for sugar, this would be 12 times 12.1 plus 22 times 1.8 plus writing on the second line because I have no space 16.0 and this should equal 342 0.2 grams per mole. And if you do this for oxygen, that would be too times 16.0 which will equal, um 32 transfer more and for CNN to that would be too time 16 on and adding its Wall 0.1. So we got 32 waas 12 his 44 point one grams per mall for water to type 1.8 waas question. And that would be 18 point 02 g Permal, right? So I'm just going thio box this so it's easier to see Okay, grift. And I'm just going to use those squiggly lines so we know that we're talking about different molecules. So now we've calculated the Mueller masses or all the molecules in our equation. So now if we're given a mass for one molecule, we can calculate the number of bulls for that molecule. So, for example, Let's say you're given 5.36 g of sugar. Using this information, we can calculate the number of moles kosher using the molar mass eso using dimensional analysis. We see that if we set up this equation like so um so if we set up this equation like so we have our given value or the value that we're starting with, which is 5.36 g and we can use eventual analysis to get moles so we can set up the smaller mass so that moles are on top and 3 g are on the bottom. So if we cited up in this manner, we see that the grams canceled ever left with bulls. So then, um, in 5.36 g of sugar, we can calculate this so that we obtain zero point 015 66 moles of shirt. And if we based the number of most of the other molecules based on this one given piece of information, we can calculate the number of wolves for everything else. And so if we wanted to calculate the moles of oxygen, you would multiply this by 12, because right now, the coefficient for sugar is one. And so if it were something else, like if this were to, then you would have to divide this by two to kind of normalize it and then use that number to calculate the other most house. In this case, the coefficient is one. And so we can just multiply this, um, by 12 for oxygen to get the number of moles. And when you do this, you get 0.18 79 malls, Hello to you. Then you get 0.1879 moles O C 02 Then you get 0.172 to 6 balls of H 20 And so here we have learned that by calculating the molar mass for all the molecules and given a piece of information like a mask, you can figure out the moles of one molecule as well as the number of moles. Were all of the other molecules in your chemical equation