A student investigates the reaction between dilute hydrochloric acid and solid calcium carbonate. A gas is produced during this reaction.
Which option correctly identifies the gas evolved, the chemical test used to confirm its identity, and the ionic equation representing the positive test reaction?
Gas: CO2(g)\text{CO}_2(g)CO2(g)
Test: Bubble the gas through limewater; it turns cloudy.
Equation: Ca2+(aq)+2OH−(aq)+CO2(g)→CaCO3(s)+H2O(l)\text{Ca}^{2+}(aq) + 2\text{OH}^-(aq) + \text{CO}_2(g) \rightarrow \text{CaCO}_3(s) + \text{H}_2\text{O}(l)Ca2+(aq)+2OH−(aq)+CO2(g)→CaCO3(s)+H2O(l)
Gas: H2(g)\text{H}_2(g)H2(g)
Test: Hold a burning splint near the gas; it burns with a squeaky pop.
Equation: 2H2(g)+O2(g)→2H2O(l)2\text{H}_2(g) + \text{O}_2(g) \rightarrow 2\text{H}_2\text{O}(l)2H2(g)+O2(g)→2H2O(l)
Gas: CO2(g)\text{CO}_2(g)CO2(g)
Test: Bubble the gas through limewater; it turns cloudy.
Equation: Ca2+(aq)+CO32−(aq)→CaCO3(s)\text{Ca}^{2+}(aq) + \text{CO}_3^{2-}(aq) \rightarrow \text{CaCO}_3(s)Ca2+(aq)+CO32−(aq)→CaCO3(s)
Gas: O2(g)\text{O}_2(g)O2(g)
Test: Hold a glowing splint in the gas; it relights.
Equation: C(s)+O2(g)→CO2(g)\text{C}(s) + \text{O}_2(g) \rightarrow \text{CO}_2(g)C(s)+O2(g)→CO2(g)
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.