Tests for anions and ammonium ionsEdexcel International A Level Chemistry: Flashcards

Exam questions on Tests for anions and ammonium ions

1. A student adds dilute hydrochloric acid to a white powder and sees vigorous effervescence. She passes the gas given off through limewater, which turns milky. The powder is known to be a sodium salt.
   The powder is sodium carbonate. A 0.53 g sample reacts with excess dilute hydrochloric acid. Calculate the maximum volume of carbon dioxide produced, in cm³, at room temperature and pressure. (Na₂CO₃: M = 106.0 g mol⁻¹; molar volume of a gas at room temperature and pressure = 24.0 dm³ mol⁻¹)2 marks
2. A technician at a swimming pool tests a sample of pool water for dissolved sulfate. He adds dilute hydrochloric acid and then barium chloride solution, and a white precipitate forms.
   Explain why dilute sulfuric acid should not be used instead of dilute hydrochloric acid to acidify the sample.2 marks
3. A soil-testing laboratory analyses a solid fertiliser that is thought to be ammonium sulfate, (NH₄)₂SO₄. Relative atomic masses: H 1.0, N 14.0, O 16.0, S 32.1, Ba 137.3.
   Describe how the laboratory could show that the fertiliser contains ammonium ions. Give the ionic equation for the reaction and the observation that identifies the gas.3 marks