 Okay, so let's try this next time. What's the mass in grams of 0.250 moles of the common antacid calcium carbonate? Okay, so what is the first thing that we have to do to figure this question out? Figure the formula for calcium carbonate. Does anybody know the formula for calcium carbonate? Calcium carbonate. Yeah, so what's calcium? Ca. And what's carbon? Well, what's the charge for calcium? Plus two. Plus two. Okay, so what's carbonate? CO3. CO3. What's the charge for it? Negative two. What was it? Sorry, I didn't hear. Negative two. Negative two it is. Good guess. I can tell from the smile. I know that the people watching can't see it. Okay, so when we combine this, these are just going to go away and smash that together. So CaCO3. Okay, so now what do we have to do that? At the atomic mass. At the atomic mass of each one of them, and that gives us the formula weight of the total thing. Okay, so let's do that. So we look at our periodic table, and calcium is 40.08. I don't have a periodic table in front of me, so if I get one wrong, tell me. Carbon is 12.01, and oxygen is 16, right? So I've got, so for the formula weight of this, it's going to be 100.09 AMU. Okay, but remember when we're doing the mass of it, we're going to have to use the molar mass, okay? Which is the same number, just grams per mole. Okay? So when we're looking for the mass of calcium carbonate, 0.250 moles. So 0.250 times 100.09 gives us the three significant figures, 25.0 grams, and hopefully that's one of the answers. Yep. Okay, so are there any questions on that one?