At `10^(-3)mm` pressure and 300 K, a 2L flask contains equal numbers of moles of `N_(2)` and water vapour. (i) what is the total number of moles of `N_(2)` and water vapour in the mixture ? (ii) what is the total mass of the mixture?

Explanation

(i) `n=(PV)/(RT)=((10^(-3)//760)xx2)/(0.0821xx300)=1.06xx10^(-7)mol`
(ii) `n_(N_(2))=n_(H_(2)O) =(n)/(2)=(1.06xx10^(-7))/(2)=5.3xx10^(-8)mol`
`therefore`Total mass`=m_(N_(2)) +m_(H_(2)O)`
`=(5.3xx10^(-8)xx28+5.3xx10^(-8)xx18)g=2.44xx10^(-6)g`