Question

Which of the following statement(s) is/are correct?
(a) Non-volatile impurities decrease the boiling point of the substance.
(b) Addition of impurities to a solid decrease the melting point of solid.
(c) Lower the boiling point of a liquid, higher is its rate of evaporation.

• A. Both (b) and (c)
• B. Both (a) and (c)
• C. Only (c)
• D. Only (a)

Answer 1

The correct option is A Both (b) and (c)

When a non-volatile impurity is added to a liquid, the fraction of the surface covered by the liquid particles gets reduced. Therefore, it requires a higher amount of energy for the liquid to boil, thus, increasing its boiling point.
An impurity added to a solid, causes its melting point to decrease because impure particles disrupt the stable crystal structure of pure solid and weaken the interparticle forces of attraction. Therefore, it requires a lesser amount of energy to melt the impure solid.
A liquid which has a low boiling point would require less energy to vaporize. This means, it would evaporate easily. Hence, the correct answer is option (a).