Mass Transfer - Engineering

Q1:

When the __________ the relative humidity of air decreases, despite an increase in the absolute humidity.

A temperature rises

B pressure rises

C temperature falls

D pressure falls

ANS:A - temperature rises

When the temperature rises, the relative humidity of air decreases, despite an increase in the absolute humidity. Relative humidity is the ratio of the partial pressure of water vapor in the air to the equilibrium vapor pressure of water at a given temperature. When the temperature rises, the equilibrium vapor pressure of water increases, but the actual partial pressure of water vapor may not increase at the same rate. As a result, the relative humidity decreases even though the absolute humidity (amount of water vapor in the air) increases. Therefore, when the temperature rises, the relative humidity of air decreases, despite an increase in the absolute humidity.