A student investigates the neutralisation of an acid by adding solid calcium hydroxide, Ca(OH)2\text{Ca(OH)}_2Ca(OH)2, to dilute nitric acid, HNO3\text{HNO}_3HNO3.
The student's method is as follows:
Step 1: Measure 120 cm3 of dilute nitric acid into a clean beaker.
Step 2: Add a 0.3 g portion of calcium hydroxide powder to the beaker.
Step 3: Measure and record the pH of the mixture.
Step 4: Repeat Steps 2 and 3 until the pH remains constant.
State one action that the student should take immediately after Step 2 to ensure that the calcium hydroxide reacts as fully as possible with the acid before the pH is measured.
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.