A sample of air contains only `N_(2), O_(2), and H_(2)O`. It saturated with water vapours and total pressure is `6 "torr"`. The vapour pressure of water is `40 "torr"` and the mol ratio of `N_(2):O_(2)` is `3:1`. The partial pressure of `N_(2)` in the sample is

Options

A. `540 "torr"`
B. `900 "torr"`
C. `1080 "torr"`
D. `450 "torr"`

Answer

D

Explanation

From Dalton's law of partial pressure
`implies P=P_(N_(2))+P_(O_(2))+P_(H_(2)O)`
`implies640=P_(N_(2))+P_(O_(2))+40`
`implies 600=P_(N_(2))+P_(O_(2))`
Now `P_(N_(2))=X_(N_(2))+(P_(N_(2))+P_(O_(2)))`
`implies P_(N_(2))=(3)/(4)xx600= 450 "torr"`