A student makes hydrated copper sulfate crystals, CuSO4⋅5H2O\mathrm{CuSO_{4}\cdot5H_{2}O}CuSO4⋅5H2O, from copper oxide and dilute sulfuric acid. She calculates a percentage yield of 108%.
Statement 1: the crystals were weighed before they were fully dry
Statement 2: she added an excess of copper oxide and filtered off the unreacted solid
Statement 3: she calculated the theoretical yield using the Mr M_r\,Mr of CuSO4\mathrm{CuSO_{4}}CuSO4 instead of the Mr M_r\,Mr of CuSO4⋅5H2O\mathrm{CuSO_{4}\cdot5H_{2}O}CuSO4⋅5H2O
Which statements could explain this result?
1 and 3 only
1 only
2 and 3 only
1, 2 and 3
157 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.