Everybody, welcome back. We're going to do a couple quick problems here. First on molar mass and then how to use molar mass to do a gram with a moles conversion. So first question here is what is the molar mass of this chemical NH4 in parentheses subscript 2s I of 4 ammonium sulfate. Sorry, silicate. So first off, you're going to need to pre-activity, you need to cut the layers. So the key for this is to know and understand what molar mass actually means. It's how many grams you would have if you had one mole that element. So those numbers in the lower box are telling you how many grams one mole meets. Well, you have to remember one mole is like the word dozen. A dozen means you have 12 of something. The mole means you have 6.02 times 10 to the 23rd of something. It's like 602 billion groups of a trillion, just a huge number. Well, that's how many of these atoms we need to have something big enough for us to measure on our balances. So that's what we're using. So molar mass of NH4 2s I of 4 you simply need to be able to figure out how much each element weighs and how many of them you have. So my first element that I've seen here is I have ends. So I look at the pre-actable and find the end and it has 14.01 grams per one mole. How many of these do I have? If I had one mole, a molar mass means I have one mole. How many moles of end do I have? Well, it's 1 times 2. So I'm going to put in times 2 here and that gives me 28.02. Okay, do the same thing for H. Find H. It's number one on the pre-actable. 1.01 is the mass for an H. But how many Hs do I have? Here I have subscript of 4 and that's a multiplier for the subscript on the outside. So 4 times 2 is 8. Multiply all that out. I get 8.08. Okay? What else do I have? I have Si's. So find Si to number 14. Silicon right here. Si as a weight. So 28.09 according to my formula, there's no subscript here, so I only have one of them. So 28.09. Last one I have is oxygen. So I have oxygen, which is right here, 16.00 for one mole of oxygen. But I have four of those. I'm going to multiply that by four. And that would be 64.00. Now this is basically telling us the weights of all of our pieces. So now I'm simply going to take the calculator and add them all together. Okay? So I have 28.02 plus 8.08 plus 28.10. Last 28.09 plus 64. That gives me 128.19 grams. And that's how many grams are equal to one mole. Or another way to write that is to say 128.19 grams per mole. Okay? So when I ask for molar mass. That is an example of how we do that.