Question

give reason
1 A decrease in temperature is observed on mixing ethanol and acetone
2 Potassium chloride solution freezes at a lower temperature than water.

Answer 1

Answer:

1. Upon mixing molecules of ethanol and acetone have strong intermolecular attraction is due to which it is evolved from the reaction system and hence cooling of mixture is observed.

2. Potassium chloride solution is a solution of non volatile solute KCl and water solution. At the freezing point of a substance the solid phase (ice) is in dynamic equilibrium with the liquid phase. A solution freezes when its vapour pressure equals the vapour pressure of pure solid solvent.

According to Raoult's law when a nonvolatile solid is added to the solvent its vapour pressure decreases and now it would become equal to that of solid solvent at lower temperature. Thus, freezing point of solvent decreases.