Question

1. the solubility of a compound is 59 g / 100 ml in boiling methanol and 30 g / 100 ml in cold methanol, whereas its solubility in water is 7.2 g / 100 ml at 95 °c and 0.22 g / 100 ml at 2 °c. which solvent would be better for recrystallization of the compound? explain (8 points).

Explanation:

Recrystallization requires a solvent where the compound has high solubility at high - temperature and low solubility at low - temperature. For methanol, the solubility difference is \(59 - 30=29\ g/100\ mL\). For water, the solubility difference is \(7.2 - 0.22 = 6.98\ g/100\ mL\). A larger solubility difference means more compound will crystallize out on cooling. Since the solubility difference in methanol is larger.

Answer:

Methanol is a better solvent for recrystallization of the compound because it has a larger difference in the solubility of the compound between high and low temperatures compared to water.