A manufacturer checks three production batches of a solid medicine ingredient. The pure ingredient melts sharply at 150 ∘C150\ ^{\circ}\text{C}150 ∘C.
The chemist records when liquid first appears and when no solid remains.
| Production batch | Temperature when liquid first appears (°C) | Temperature when no solid remains (°C) |
|---|---|---|
| 24 | 147 | 149 |
| 31 | 144 | 148 |
| 38 | 138 | 148 |
The batch containing the most impurities cannot be used.
State which batch must be discarded and explain how the results support this decision.
102 exam-style questions on OCR GCSE Chemistry 2.1 Purity and separating mixtures, covering 2.1.1 Pure substances and melting point data, 2.1.2 Relative formula mass and empirical formula, 2.1.3 Formulations as useful mixtures, 2.1.4 Techniques for separating mixtures, and 2.1.5 Chromatography and Rf values. Each one has a worked solution and a mark scheme showing where the marks go.