Required Practical Preparations — Acids, Bases and Salt Preparations | IGCSE Chemistry

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 8% of your exam marks.

stable

Low

Stable8%

Soluble and insoluble salt preparation methods are consistently tested with multi-step answers.

Apparatus: 100 cm³ beaker; measuring cylinder; spatula and stirring rod; Bunsen burner, tripod, gauze and heatproof mat; filter funnel, filter paper, conical flask; evaporating basin
Materials: dilute sulfuric acid (1.0 mol dm⁻³); solid copper(II) oxide
Method:
- Measure 40 cm³ of dilute sulfuric acid into the beaker and warm it gently with the Bunsen
- Add black copper(II) oxide powder a spatula-tip at a time, stirring, until no more dissolves — undissolved black solid in a clear blue solution means the base is in excess
- Filter the warm mixture; the blue filtrate is impure copper(II) sulfate solution, and the black residue is the unreacted copper(II) oxide
- Pour the filtrate into an evaporating basin and warm gently until crystallisation just begins on a cold glass rod
- Set the basin aside in a warm place for several hours to let bright-blue hydrated copper(II) sulfate crystals form slowly
- Decant any remaining mother liquor and dry the crystals between sheets of filter paper
Word and symbol equations:

copper(II) oxide + sulfuric acid → copper(II) sulfate + water
CuO(s) + H₂SO₄(aq) → CuSO₄(aq) + H₂O(l)

Final product appearance: well-formed, deep-blue, regular-shaped crystals of CuSO₄·5H₂O

Apparatus: 100 cm³ beaker; measuring cylinder; stirring rod; filter funnel, filter paper, conical flask; wash bottle of distilled water; watch glass; oven or warm cupboard for drying
Materials: aqueous lead(II) nitrate (0.4 mol dm⁻³); aqueous potassium sulfate (0.4 mol dm⁻³)
Lead salts are toxic — wear gloves and dispose of waste solutions in the chemical-waste container, not down the sink
Method:
- Measure 30 cm³ of lead(II) nitrate solution into the beaker
- Add 30 cm³ of potassium sulfate solution and stir briefly — a fine white precipitate of lead(II) sulfate appears immediately
- Filter the mixture, keeping the white residue on the filter paper; the clear filtrate is potassium nitrate solution and is discarded
- Wash the residue twice with a few cm³ of distilled water from a wash bottle, letting each wash drain through completely
- Transfer the washed solid to a watch glass and dry it in a warm oven
Word and symbol equations:

lead(II) nitrate + potassium sulfate → lead(II) sulfate + potassium nitrate
Pb(NO₃)₂(aq) + K₂SO₄(aq) → PbSO₄(s) + 2 KNO₃(aq)