A metal supplier checks four pieces from unlabelled stock. Each piece is heated and its melting behaviour is recorded.
| Stock code | Melting temperature in ∘C^\circ\text{C}∘C |
|---|---|
| N4 | 232 |
| P7 | 327 |
| R3 | 183 to 215 |
| T6 | 660 |
The supplier requires each piece to be a pure substance.
Based on the melting test, give the stock code that fails this requirement.
113 exam-style questions on AQA GCSE Chemistry 8.1 Purity, formulations and chromatography, covering 8.1.1 Pure substances, 8.1.2 Formulations, and 8.1.3 Chromatography. Each one has a worked solution and a mark scheme showing where the marks go.