A student carries out a titration to find the exact volume of dilute nitric acid needed to neutralise 20.0 cm3 of sodium hydroxide solution, using methyl orange indicator.
To obtain a pure, dry sample of solid sodium nitrate, the student repeats the reaction by mixing the same exact volumes of the acid and alkali, but this time without adding the indicator. They then evaporate the water from this new mixture.
Explain why the student must prepare this new mixture without the indicator, rather than evaporating the mixture from the titration, to obtain a pure sample of solid sodium nitrate.
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.