Density of dry air (only `N_(2) and O_(2)`) is `124 g "litre"^(-1)` at 760 mm and 300 K. Find the partial pressure of `N_(2)` gas in air (Take `R = (1)/(12)` litre atm/mol K , mol. wt. of `N_(2)` = 28)

Options

A. `0.25`
B. `0.35`
C. `0.5`
D. `0.75`

Answer

1

Explanation

`d_(mix)=(PM_(mix))/(RT)`
`1.2(1atmxxM_(mix))/((1)/(12)xx300)`
`M_(mix)=1.24xx25=21`
`M_(mix)=X_(O_(2))xxM_(O_(2))+(1-X_(O_(2)))M_(N_(2))`
`31=x xx32+(1-x)28`
`x=(3)/(4)`
`:." "P_(O_(2))=x_(O_(2))xxP_(T)=(3)/(4)atm`
`P_(N_(2))=(1)/(4)ATM=0.25atm`