I surprised myself by working out a fairly obvious way of working out percentage yield in a chemical reaction. We weighed out 2 grams of marble chips and added 40 cubic centimetres of 1M hydrochloric acid. The reaction produces carbon dioxide so we weighed the whole conical flask at the start and then at the end. It had got lighter because the carbon dioxide escapes into the air.
By using relative formula mass we could calculate the expected mass of carbon dioxide and compare it with the actual mass, thus allowing percentage yield to be calculated.
