ANS:B - reduce drying temperature.

Drying operation under vacuum is carried out to reduce drying temperature. Explanation:

1. Reduced Pressure:
   • When drying is conducted under vacuum, the pressure inside the drying chamber is reduced below atmospheric pressure.
   • Lowering the pressure reduces the boiling point of the liquid moisture present in the material being dried.
   • As a result, the moisture evaporates at lower temperatures compared to drying under atmospheric pressure.
2. Temperature Reduction:
   • By lowering the pressure, the drying temperature required to remove moisture from the material can be reduced.
   • This is particularly beneficial for heat-sensitive materials that may degrade or undergo undesirable chemical reactions at higher temperatures.
   • Drying under vacuum allows for gentler drying conditions, minimizing the risk of thermal degradation and preserving the quality of the material being dried.
3. High Bound Moisture Content:
   • Vacuum drying is not specifically aimed at drying materials with high bound moisture content.
   • Bound moisture is typically removed through other drying methods that involve breaking chemical bonds or releasing moisture through physical or chemical means.