A solid pigment is made by the same reaction in repeated batches. A new filtering method is introduced after the first set of batches.
| Filtering method | Percentage yield | Atom economy |
|---|---|---|
| original | 68% | 74% |
| new | 82% | 74% |
Why can the new filtering method change the percentage yield without changing the atom economy?
It can separate the by-product from the pigment, but atom economy includes only the desired product.
It can increase the theoretical yield, but atom economy is measured before the pigment is filtered.
It can make more of the reactants react, but atom economy depends only on the reactants used.
It can reduce practical losses of pigment, but atom economy is fixed by the balanced equation.
151 exam-style questions on Edexcel GCSE Chemistry 6.2 Quantitative analysis, covering 6.2.1 Concentration in mol dm⁻³ and titration calculations, 6.2.2 Percentage yield and why actual yield falls short, 6.2.3 Atom economy of a reaction, 6.2.4 Choosing a reaction pathway, and 6.2.5 Molar volume of gases and Avogadro's law. Each one has a worked solution and a mark scheme showing where the marks go.