A volume V of air saturated with water vapour experts a pressure P. Pressure of saturated vapour is `P_(0)`. If the volume is made `V//2` isothermally, the final pressure will be

Options

A. `P`
B. `2 P_(0)`
C. `2P + P_(0)`
D. `2(P - P_(0))`

Answer

B

Explanation

The saturated vapour pressure depends only on temperature , so it remains constant irrespective of change in volume.
pressure of air = `(P-P_(0))`
When volume of air is halved at constant temperature, its pressure is doubled
so, `P_(air)^(') = 2(P-P_(0))`
`:.` Total pressure
`P' = P_(air)^(') + P_(0) = 2(P-P_(0))+P_(0)=2P-P_(0)`.