Group 2 compounds and their usesAQA A-Level Chemistry: Subtopic test

1. 1
   Magnesium hydroxide is sparingly soluble in water. Group 2 hydroxides are used in medicine and in agriculture.

   (a)

   Which Group 2 compound is added to acidic soil to raise its pH?

   [1 mark]

   • AMg(OH)₂
   • BCa(OH)₂
   • CBaSO₄
   • DCaSO₄

   (b)

   Why is magnesium hydroxide, rather than sodium hydroxide, used in indigestion remedies?

   [1 mark]

   • AIt is sparingly soluble, so the solution is only mildly alkaline and not corrosive
   • BIt is more soluble than sodium hydroxide
   • CIt is a strong acid
   • DIt contains no hydroxide ions

   (c)

   Write an equation for the reaction of magnesium hydroxide with hydrochloric acid in the stomach, and explain how this relieves indigestion.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student tests three colourless solutions, sodium sulfate, sodium carbonate and sodium chloride, by adding acidified barium chloride solution to a sample of each.

   (a)

   What is observed when acidified barium chloride solution is added to sodium sulfate solution?

   [1 mark]

   • ANo change
   • BA white precipitate that dissolves
   • CA white precipitate that remains
   • DA yellow precipitate

   (b)

   Which ionic equation represents the reaction that identifies the sulfate?

   [1 mark]

   • ABa²⁺(aq) + 2Cl⁻(aq) → BaCl₂(s)
   • BNa⁺(aq) + Cl⁻(aq) → NaCl(s)
   • CBa²⁺(aq) + CO₃²⁻(aq) → BaCO₃(s)
   • DBa²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)

   (c)

   Explain why the barium chloride solution is acidified when testing for sulfate ions.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A coal-fired power station removes sulfur dioxide from its flue gases using calcium compounds. Relative atomic masses: Ca 40.1, C 12.0, S 32.1, O 16.0.

   (a)

   Calcium oxide reacts with sulfur dioxide in the flue gases. Write an equation for this reaction and explain why the reaction takes place and why the sulfur dioxide must be removed.

   [3 marks]

   (b)

   The flue gases contain 640 kg of sulfur dioxide per hour. Calcium carbonate reacts with it: CaCO₃ + SO₂ → CaSO₃ + CO₂. Calculate the mass of calcium carbonate needed per hour, in kg, to remove all of the sulfur dioxide.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A hospital laboratory handles barium and magnesium compounds. Barium sulfate is swallowed as a 'barium meal' before X-ray images of the digestive system are taken. Two colourless stock solutions, one containing Mg²⁺ ions and one containing Ba²⁺ ions, have lost their labels.

   (a)

   Explain why barium sulfate can be swallowed safely for an X-ray image of the digestive system, although soluble barium compounds are toxic.

   [6 marks]

   (b)

   Describe two tests, using the solubility trends in Group 2 compounds, that would show which stock solution contains Mg²⁺ and which contains Ba²⁺. Include observations and ionic equations.

   [6 marks]

   Total for question 4: 12 marks

End of questions