The percentage yield of a reaction compares two quantities.
Which two quantities are compared?
Mass of product made and total mass of reactants used
Mass of useful product and total mass of all products formed
Mass of product actually made and maximum theoretical mass of product
Mass of reactant left over and starting mass of the reactant
39 exam-style questions on AQA GCSE Chemistry 3.3 Yield and atom economy of chemical reactions, covering 3.3.1a Percentage yield, 3.3.1b Theoretical mass of a product, 3.3.2a Atom economy, and 3.3.2b Choosing a reaction pathway. Each one has a worked solution and a mark scheme showing where the marks go.