Which of the following is an undesirable property for an absorbing solvent ?

ANS:D - None of these

The correct answer "None of these" indicates that none of the properties listed are inherently undesirable for an absorbing solvent. Let's examine why:

1. Low vapor pressure: A low vapor pressure is generally desirable for an absorbing solvent because it helps maintain a stable concentration of the solvent in the gas phase, which is essential for effective absorption. High vapor pressure could lead to excessive losses of the solvent to the gas phase.
2. Low freezing point: A low freezing point is also generally desirable because it ensures that the solvent remains in liquid form over a wide range of operating temperatures. This prevents the solvent from solidifying, which could disrupt the absorption process and cause operational issues.
3. Low velocity: While a very low velocity might not provide sufficient mixing and contact between the solvent and the gas phase, a moderate to high velocity is typically desirable to ensure efficient mass transfer and absorption. However, a "low" velocity in itself may not be inherently undesirable if it still allows for adequate contact and mass transfer.

Therefore, none of the properties listed—low vapor pressure, low freezing point, or low velocity—are universally undesirable for an absorbing solvent. Each property has its own specific role and significance in the absorption process, and their desirability depends on the specific requirements and conditions of the absorption system.