CIE iGCSE Co-Ordinated Science C7.3 Preparation of salts Exam Style Questions Paper 1

This question describes the preparation of a soluble salt (copper sulfate) by adding an excess insoluble metal carbonate (copper carbonate) to dilute sulfuric acid.

Step 1: The mixture is filtered to remove the excess unreacted copper carbonate. The filtrate is the copper sulfate solution. (Boiling would not remove the solid).

Step 2: The filtrate is then heated to evaporate some of the water, decreasing the volume and making the solution more concentrated (saturated). (Cooling at this stage would not decrease the volume).

Step 3: The concentrated solution is then left to cool. As it cools, the solubility of copper sulfate decreases, and pure copper sulfate crystals form. (Evaporating to dryness would give a powder, not well-formed crystals, and could decompose the hydrated salt).

Therefore, the correct sequence is filtered, heated, left to cool, which matches row D.

✅ Answer: (D)