Pure benzoic acid melts at 122 ∘C122\,^\circ\mathrm{C}122∘C. Three samples, each labelled "benzoic acid", are tested.
| Sample | Melting behaviour |
|---|---|
| W | melts sharply at 122 ∘C122\,^\circ\mathrm{C}122∘C |
| X | melts gradually from 114 ∘C114\,^\circ\mathrm{C}114∘C to 119 ∘C119\,^\circ\mathrm{C}119∘C |
| Y | melts sharply at 131 ∘C131\,^\circ\mathrm{C}131∘C |
Statement 1: sample X contains impurities
Statement 2: sample Y is benzoic acid containing an impurity that raises its melting point
Statement 3: sample Y is probably a pure substance, but it is not benzoic acid
Which statements are correct?
1 only
1 and 2 only
1 and 3 only
2 and 3 only
107 exam-style questions on Edexcel GCSE Chemistry 3.2 Methods of separating and purifying substances, covering 3.2.1 Pure substances and mixtures, 3.2.2 Techniques for separating mixtures, 3.2.3 Paper chromatography and Rf values, and 3.2.4 Making water potable. Each one has a worked solution and a mark scheme showing where the marks go.