ANS:D - all (a), (b) and (c).

When absorption occurs with the evolution of heat compared to isothermal absorption, several differences can be observed:

1. Decreased Solute Solubility: Absorption with the evolution of heat typically results in decreased solute solubility compared to isothermal absorption. This is because the increase in temperature reduces the solubility of the solute in the solvent. As the solvent temperature increases, its ability to hold the solute decreases, leading to decreased solubility.
2. Large Minimum Liquid to Gas (L/G) Ratio: Absorption with the evolution of heat may require a larger minimum liquid to gas (L/G) ratio compared to isothermal absorption. This is because the increased temperature can lead to increased vaporization of the solvent, requiring more liquid to maintain the desired concentration of solute in the solvent.
3. Large Number of Trays: Depending on the specific conditions and requirements of the process, absorption with the evolution of heat may also require a larger number of trays in the column compared to isothermal absorption. This could be due to factors such as increased vaporization of the solvent and the need for more stages to achieve the desired separation efficiency.