ANS:C - both (a) and (b).

Certainly! Let's break down why the amount of steam required per unit quantity of distillate in steam distillation will be reduced by raising the temperature and lowering the total pressure:

1. Raising the Temperature:
   • Increasing the temperature in a steam distillation process promotes the vaporization of the volatile components in the mixture.
   • As temperature increases, the vapor pressure of the volatile components also increases, leading to more efficient vaporization.
   • With higher temperatures, the volatile components evaporate more readily from the mixture, requiring less steam to carry them away.
   • Therefore, raising the temperature in steam distillation reduces the amount of steam required per unit quantity of distillate.
2. Lowering the Total Pressure:
   • Lowering the total pressure in a steam distillation process reduces the boiling point of the mixture.
   • At lower pressures, the vapor pressure of the volatile components becomes sufficient to overcome the reduced external pressure, causing them to vaporize more readily.
   • As a result, less energy (steam) is needed to vaporize the volatile components, leading to a reduction in the amount of steam required per unit quantity of distillate.
   • Lowering the total pressure effectively reduces the energy input required for vaporization.
3. Both (a) and (b):
   • Both raising the temperature and lowering the total pressure work synergistically to enhance the efficiency of vaporization in steam distillation.
   • Raising the temperature increases the kinetic energy of the molecules, facilitating vaporization, while lowering the total pressure reduces the external resistance to vaporization.
   • Together, these factors lead to a reduction in the amount of steam required per unit quantity of distillate, making the process more efficient.

In summary, both raising the temperature and lowering the total pressure in steam distillation contribute to reducing the amount of steam required per unit quantity of distillate, making the process more energy-efficient and cost-effective. Therefore, the correct answer is: both (a) and (b).