Calculate `DeltaS` for the formation of quantity of air containing 1 mole of a gas by mixing nitrogen and oxygen. (In air `N_(2) = 80%`and `O_(2) =20%)`

Explanation

The mole fraction fo nitrogen and oxygen in air are:
`chi_(N_(2))=0.8`
`chi_(O_(2)) = 0.2`
`Delta_(mix)S =- nR sum chi_(i) In chi_(i)`
`=- (1.0 mol) (8.314 J K^(-1)mol^(-1)) [0.8 In 0.8 +0.2 In 0.2]`
`=(-8.314 J K^(-1)) (-0.1785 - 0.3219)`
`= 4.160 J K^(-1)`