A student carried out a titration to find the exact volume of dilute nitric acid needed to neutralise 20.0 cm3 of sodium hydroxide solution. Phenolphthalein indicator was used to identify the end point.
The student then mixed a fresh 20.0 cm3 sample of sodium hydroxide solution with the exact volume of nitric acid determined from the titration, but without adding any indicator. This new mixture was then heated to evaporate most of the water and left to crystallise.
Explain why this new mixture was evaporated to produce a pure sample of solid sodium nitrate, rather than the mixture remaining at the end of the titration.
276 exam-style questions on Edexcel GCSE Chemistry 4.1 Acids, covering 4.1.1 Acids, alkalis and the pH scale, 4.1.2 Hydrogen ion concentration and pH, 4.1.3 Dilute and concentrated, weak and strong acids, 4.1.4 Bases, alkalis and the reactions of acids, 4.1.5 Chemical tests for hydrogen and carbon dioxide, 4.1.6 Neutralisation as a reaction of acids with bases, 4.1.7 Preparing soluble salts, and 4.1.8 Solubility rules and preparing insoluble salts. Each one has a worked solution and a mark scheme showing where the marks go.