Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A solid mixture of calcium carbonate and sodium hydrogencarbonate has a mass of . It is heated strongly, at about , until the mass stops changing. The solid left is calcium oxide and sodium carbonate, and the mass lost is . The reactions are and . Use , , and for CO, HO, CaCO and NaHCO. Find the mass of calcium carbonate in the mixture, the mass of carbon dioxide given off and its volume at and , with .
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. Each solid loses a fixed fraction of its mass. Write the total loss with one unknown.
Step 1. The fractions. Calcium carbonate: . Sodium hydrogencarbonate: .
Step 2. The equation. , so and .
Step 3. The carbon dioxide. From the calcium carbonate: . From of sodium hydrogencarbonate (), half a mole of CO for each mole: . The total is .
Step 4. Volume. .
Answer: , and .
Watch out. The water that sodium hydrogencarbonate gives off is lost mass too, but it is not a gas that we count, since it is steam. Only half a mole of CO comes from each mole of NaHCO.
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A gas at and has a molar volume of . Calcium hydroxide takes up carbon dioxide mole for mole: . When a mixture loses mass on heating, the loss of each solid is its fraction of CO (and water) times its mass.