When air containing unsaturated water vapour is cooled at constant atmospheric pressure without adding or removing moisture, the saturated vapour pressure of water decreases while the actual partial vapour pressure of water remains constant until the dew point is reached.
Answer: Answer
Answer
True. Saturated vapour pressure decreases as temperature falls, while actual partial vapour pressure remains constant under constant total pressure until condensation starts at the dew point.
The statement is correct because saturated vapour pressure is a temperature-dependent property that decreases as air cools. So long as total pressure remains unchanged and no water vapour is added or removed, the actual partial vapour pressure of the water vapour stays constant until the dew point is reached, at which point the air becomes saturated ( relative humidity) and condensation begins.
Step-by-Step Solution
Key Concept
Saturated vs. actual vapour pressure, temperature dependence of SVP, and dew point