A-LevelChemistryEquilibriaOct/Nov 2018Paper 5 Q112 Marks
A sample of waste water contains calcium ions, copper(II) ions and lead(II) ions. You are to plan an experimental procedure to separate the metal ions in the waste water sample by forming precipitates of the metal ions. The table shows the numerical values of the solubility products, Ksp, of some compounds. For example, the solubility product of calcium chloride, Ksp = [Ca²⁺][Cl⁻]² = 2 × 10¹ mol³ dm⁻⁹. The smaller the solubility product, the easier it is for a precipitate to form. Ksp values | | Cl⁻ | CO₃²⁻ | S²⁻ | |:---|:---|:---|:---| | Ca²⁺ | 2 × 10¹ | 5 × 10⁻⁹ | 3 × 10⁻¹⁰ | | Cu²⁺ | 1 × 10¹ | 3 × 10⁻¹⁰ | 6 × 10⁻³⁶ | | Pb²⁺ | 2 × 10⁻⁵ | 7 × 10⁻¹⁴ | 3 × 10⁻²⁸ | You are provided with * a sample of waste water containing Ca²⁺(aq), Cu²⁺(aq) and Pb²⁺(aq), * HCl(aq), * (NH₄)₂CO₃(aq), * (NH₄)₂S(aq). No other reagents should be used. Standard laboratory equipment is available.
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