A student investigated the rate of reaction between magnesium ribbon and dilute hydrochloric acid.
They repeated the experiment using different concentrations of dilute hydrochloric acid to see how this affected the volume of hydrogen gas collected in the first 2 minutes.
State one variable that should be controlled in this investigation to ensure a valid set of results.
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.