Question

What are the characteristics of the solvent used during purification of copper sulphate by crystallization?

• A. Not dissolve the substance at room temperature
• B. Dissolve the impurities at room temperature
• C. Does not dissolve the impurities at high temperature
• D. All of the above

Answer 1

Answer: (D)

All of the above

Choosing an appropriate solvent is the important process of crystallisation, as crystallisation works only when a proper solvent is used. It is important to choose a solvent that will not dissolve the substance at room temperature. But as the temperature of the solvent increases, the solubility of the solute also increases. At the same time, the impurities that are present must either be soluble in the solvent at room temperature or must be insoluble in the solvent at a high temperature. If the solvent is not hot when the dissolution is carried out, too much solvent will be used, leading to diminished yield.