 OK, solid calcium oxide and gaseous carbon dioxide will react to form solid calcium carbonate, according to the reaction that's posted on the board. So if we had 56.08 grams of calcium oxide and 44.0 grams of carbon dioxide, what would be the total mass of the reactants? OK, so the first thing we want to do is write down what they give us. So this is 56.08 grams of calcium oxide and 44.00 grams of carbon dioxide. So it asks us, what would be the total mass of the reactants? How would we go about doing that? Pretty obvious, right? How would we go? Add them together, right? So 56.00 plus 44, or 0.08 plus 44.00 grams. So how many sig figs, or how would we do sig figs on this? That's the question, right? So this would be 100.08. So this has four sig figs, this has four sig figs, but this has five. Is this the right way to do this? Why? After the decimal, it's very good. Yes, it's the amount after the decimal place when you're doing addition and subtraction. OK, recall that one. OK, so this would be the answer to the first question. Is everybody OK with that? So what would be the total mass of the products after this reaction? Can somebody help me out with that one? How would I figure that out? What would it be? Why? Because the law of conservation of mass tells us that mass cannot be created or destroyed. So the number over here should be the same as the number over here, right? Because we can't destroy or create after this, OK? So what would be the total mass over here? 100.08. OK, and I guess that's all we can do on this one, because there's not two products. Any questions on law of conservation of mass? Pretty straightforward, I think.