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Chemical formulae, equations and calculations

Chemical formulae, equations and calculations

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Question 12

Sodium thiosulfate solution and dilute hydrochloric acid react together slowly to form a precipitate of sulfur, which makes the mixture cloudy.

The equation for the reaction is:

Na2S2O3(aq)+2HCl(aq)→2NaCl(aq)+H2O(l)+S(s)+SO2(g) \text{Na}_2\text{S}_2\text{O}_3(\text{aq}) + 2\text{HCl}(\text{aq}) \rightarrow 2\text{NaCl}(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{S}(\text{s}) + \text{SO}_2(\text{g}) Na2​S2​O3​(aq)+2HCl(aq)→2NaCl(aq)+H2​O(l)+S(s)+SO2​(g)

A student performs an experiment using the following conditions:

  • Concentration of sodium thiosulfate solution = 0.250 mol/dm3
  • Volume of sodium thiosulfate solution = 30 cm3
  • Volume of water = 15 cm3
  • Volume of hydrochloric acid = 15 cm3 (the hydrochloric acid is in excess)
a.

Calculate the mass of sulfur dioxide, SO2\text{SO}_2SO2​, formed in this experiment. (ArA_rAr​: O=16\text{O} = 16O=16, S=32\text{S} = 32S=32)

[4]
b.

The solubility of sulfur dioxide at room temperature is 90 g/dm3. Use this information to explain whether any sulfur dioxide gas escapes from the flask during the experiment.

[3]
Markscheme

Chemical formulae, equations and calculations Questions

  1. IGCSE
  2. /Chemistry
  3. /Chemical formulae, equations and calculations

80 exam-style questions on Edexcel IGCSE Chemistry Chemical formulae, equations and calculations. Each one has a worked solution and a mark scheme showing where the marks go.

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