A chemist develops a reaction to make a ceramic pigment, P.
A+2B→P+W\text{A} + 2\text{B} \rightarrow \text{P} + \text{W}A+2B→P+W
A is the limiting reactant, but the reaction may not go to completion. B is added in excess. P is the desired product and W is a waste product. The chemist knows the balanced equation and the relative formula masses, and measures the mass of purified P collected.
Which other measurement is needed to calculate the percentage yield, but is not needed to calculate the atom economy?
The mass of reactant A used.
The mass of waste product W collected.
The mass of pigment P lost during purification.
The mass of reactant B added.
152 exam-style questions on OCR GCSE Chemistry 5.1 Monitoring chemical reactions, covering 5.1.1 The technique of titration, 5.1.2 Theoretical mass, percentage yield and atom economy, 5.1.3 Concentration of a solution in mol/dm3, 5.1.4 Concentration calculations and titration results, 5.1.5 Molar gas volume and volumes of gases in reactions, and 5.1.6 Choosing a reaction pathway. Each one has a worked solution and a mark scheme showing where the marks go.