A laboratory needs a pure sample to use as a reference when identifying an unknown solid by comparing melting points. The pure reference substance has a melting point of 156 °C. A supplier claims that batch M is pure. The results of testing batch M are shown.
| Batch | Melting range (°C) |
|---|---|
| M | 151 to 155 |
Explain whether batch M is suitable for use as the reference sample.
A technician adds a small amount of a different substance to a portion of batch M. Predict how the width of its melting range is likely to change, and explain why.
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.