ANS:D - all (a), (b) & (c)

A good solvent used for absorption should not have very high:

• Viscosity
• Vapor pressure
• Freezing point

Therefore, the correct option is all (a), (b) & (c). Here's why each of these factors is important:

1. Viscosity: High viscosity can impede the mass transfer process by slowing down the diffusion of the solute molecules into the solvent. A lower viscosity allows for faster mixing and contact between the solvent and solute, enhancing the absorption efficiency.
2. Vapor pressure: A high vapor pressure implies that the solvent will tend to evaporate more readily, potentially leading to losses and difficulties in maintaining a stable solvent concentration. A lower vapor pressure is preferable for maintaining the desired concentration of the solvent in the gas phase.
3. Freezing point: A high freezing point can limit the operating temperature range of the absorption process, especially in colder environments. Using a solvent with a lower freezing point ensures operational flexibility and prevents the solvent from solidifying at typical operating temperatures.

By avoiding high values for viscosity, vapor pressure, and freezing point, a solvent can better fulfill its role in the absorption process, leading to more efficient and reliable operation.