A sample of air contains only `N_(2), O_(2)` and `H_(2)O`. It is saturated with water vapours and the total pressure is 640 torr. The vapurs of water is 40 torr and the molar ratio of `N_(2) : O_(2)` is `3 : 1`. The partial pressure of `N_(2)` in the sample is

Options

A. 480 torr
B. 600 torr
C. 525 torr
D. 450 torr

Answer

D

Explanation

Total pressure of mixture of `N_(2), O_(2)` and `H_(2)O` is 640 torr.
Since vapour pressure of water = 40 torr
Hence pressure of `N_(2)` and `V_(2)`
`= 640 - 40 = 450` torr
Partial pressure of `N_(2)`
= mole fraction of `N_(2) xx` total pressure
`= 3//4 xx 600 = 450` torr