in this video we're going to focus on finding the molar mass of a compound so let's start with the basics what is the m mass of Elemental nitrogen not nitrogen as a diatomic molecule but as an atom well if you go to the periodic table you'll see two numbers the atomic number of seven and the average atomic mass of 14.01 the mass is equivalent to this number it's 14.01 G per Mo the molar mass is basically it connects Mass with moles so that's the M mass of n it's 14.01 G per mole so what that means is that one mole of nitrogen has a mass of 14.01 G so let's say if we wanted to find the molar mass of atomic Florine Florine has an atomic number of n but a mass number of 19 so this is the m mass of Florine it's 19 G per mole so every mole of Florine atoms has a mass of 19 G now what about some other molecules for example let's find The M mass of O3 this is Ozone it's found in the upper atmosphere and S8 Elemental sulfur find The M mass of these molecules O3 contains three oxygen atoms now if you go to the periodic table and you look for the average atomic mass of oxygen you're going to see two numbers eight and 16 the larger of these two is always the molar mass so the atomic mass of oxygen is 16 if you multiply by 3 that's 48 so the M mass of ozone O3 it's it's 48 G per Mo now what about the M mass of sulfur S8 so what we have is eight sulfur atoms and the average atomic mass of each sulfur atom is 32.7 so what we need to do is multiply 32.7 by 8 and so this will give us the M mass of sulfur it's 25656 G per mole so as you can see it's very easy to calculate the mol mass of something but let's try some harder examples go ahead and find the mol mass of carbon dioxide perhaps you've seen it as dry ice and also silicon tetrafluoride so feel free to pause the video and try these examples so CO2 contains one carbon atom and two oxygen atoms now the atomic mass of carbon is 12.01 and oxygen is 16 so 2 * 16 and that's 32 and 32 + 12 is 44 so the M mass of carbon dioxide is 44.1 G per mole now let's do this same thing for silicon tetrafluoride so we have a single silicon atom and four Florine atoms the atomic mass of silicon is 28.9 the average atomic mass of Florine is 19 19 * 4 is 76 now let's add that to 28.9 so therefore the M mass of silicon Tetra fluide is 10409 G per mole so this is the answer now let's work on another example that has more elements C6 h126 this is glucose perhaps you've seen it in BIO it's basically a molecule that provides energy for cells so go ahead and calculate the M mass of glucose so we have six carbon atoms 12 hydrogen atoms and six oxygen atoms what I like to do is I like to separate the elements so there's a as you can see there's a process in which I like to calculate the M Mass each carbon atom has an atomic mass of 12. 0 1 and each hydrogen atom if you look at the periodic table it's 1.8 and we've seen oxygen multiple times so we know the atomic mass is 16 now 6 * 12 is 72 and 6 * 01 is 06 12 * 1 is 12 12 * 8 is 96 so this is going to be 096 and 6 * 16 is also 96 so now all we need to do is simply add these numbers together so the answer that I have is 18056 G per mole so that's the mol mass of glucose a typical monosaccharide sometimes you may need to find the M mass of a substance for which you're not given the chemical formula like this one what is the m mass of calcium phosphate before we could find it you got to write the formula so you need to know that calcium phosphate is an ionic compound it's composed of a metal and some non-metals so we need to find the charges calcium has a positive two charge it's in group two of the P table and phosphate is just one of those polyatomic ions you need to know so the formula is going to be ca3 p42 you need to switch to charges with the subscripts and reverse them so this substance has three calcium atoms two phosphorus atoms and eight oxygen atoms 2 * 4 is 8 now each calcium atom has an atomic mass of 40.8 phosphorus is 30.9 7 and oxygen has an atomic mass of 16 now 3 * 40 is 120 8 * 3 is24 2 * 30.9 7 that's going to be 61.94 and 8 * 16 is 128 so now we just need to add these three numbers so I got 31018 G per mole so that's the answer that's the M mass of calcium phosphate so here's another example like the last problem in this problem you got to write the chemical formula first before you could find The M Mass so what is the chemical formula of vadium 5 hydrogen phosphate so vadium is a metal hydrogen phosphate is a polyatomic ion composed of non-metals so we have an ionic compound again now the Roman numeral tells you the charge on vadium so in this example vadium has a positive five charge hydrogen phosphate is HP4 you have a hydrogen attached to a phosphate molecule phosphate is P4 with a neg3 charge hydrogen is H+ when you combine these two you get hydrogen phosphate which is hpo4 and then you add 1 and -3 and that will give you -2 so that's the chemical formula of the hydrogen phosphate polyamic now let's use use the same method to write the formula of this substance so it's going to be V2 HP4 * 5 whenever you have multiple polyatomic ions within a compound you need to enclose it inside a parentheses so now that we have the chemical formula of vadium 5 hydrogen phosphate we can now calculate the M Mass so we have two vadium atoms and then we have 1 * 5 so five hydrogens 1 * 5 five phosphorus atoms and then 4 * 5 20 oxygen atoms so now let's look up vadium in a periodic table vadium has an atomic mass of 50.94 hydrogen is 1.08 phosphorus 3.97 and Oxygen 16 so first let's multiply 2 by 50.94 so that's 10.88 and then 5 * 1.8 that's going to be 5.04 and then 5 * 3.97 that's 154.50 and 20 * 16 is 320 so now let's add up these four numbers so I got 58177 G per mole so that's the M mass of vadium 5 hydrogen phosphate