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Edexcel IGCSE Chemistry 2.40C Preparing a Pure, Dry Soluble Salt

Practise describing how titration, controlled evaporation, crystallisation and drying produce a pure soluble salt from an acid and alkali.

Syllabus
First assessment 2019
Course
Chemistry 4CH1

Exam points

  • repeat the titration without indicator using the measured acid and alkali volumes
  • evaporate gently to the crystallisation point, then cool to form crystals
  • filter and dry the crystals without strong heating that could cause decomposition

2.40C Preparing soluble salts by titration question 1

[Maximum number: 4]

Sodium sulfate can be prepared by the reaction between sodium hydroxide solution and sodium hydrogensulfate ( NaHSO4\mathrm{NaHSO}_{4} ) solution.

This is the equation for the reaction.

NaOH(aq)+NaHSO4(aq)→Na2SO4(aq)+H2O(l)\mathrm{NaOH}(\mathrm{aq})+\mathrm{NaHSO}_{4}(\mathrm{aq}) \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})

Sodium hydrogensulfate solution is acidic.
A student adds 25.0 cm325.0 \mathrm{~cm}^{3} of sodium hydroxide solution to a conical flask and adds two drops of indicator.

The student does a titration.

The student repeats the titration without the indicator and forms a solution of sodium sulfate.

Describe how the student can obtain pure, dry crystals of hydrated sodium sulfate from the solution.

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