Question

Why is crystallisation is used for obtaining pure copper sulphate from an impure sample rather than evaporation?

• A. The impurities left after filtration may contaminate copper sulphate on evaporation.
• B. Because crystallisation is comparatively easier than evaporation
• C. Because crystallisation is comparatively faster
• D. All of the above

Answer 1

Answer: (A)

The impurities left after filtration may contaminate copper sulphate on evaporation.

Only in the crystallization technique, solids do not get separated with solvent and they also do not decompose or get charred on heating to dryness. But, in the case of the evaporation technique, solids get evaporated with solvent. Impurities also remain dissolved in the solution after filtration and can contaminate the solid copper sulphate.