The equilibrium constant `K_(p)` for the following reaction is `4.5`
`N_(2)O_(4)(g)hArr2NO_(2)(g)` What would be the average molar mass `("in"g//mol)` of an equilibrium mixture of `N_(2)O_(4)` and `NO_(2)` formed by the dissociation of pure `N_(2)O_(4)` at a total pressure of `2` atm ?

Options

A. `69`
B. `57.5`
C. `80.5`
D. `85.5`

Answer

B

Explanation

`K_(P) = (4prop^(2))/(1 - prop^(2)) P`
`P = 2 atm , K_(P) = (9)/(2)`
`prop =` degree of dissociation of `N_(2)O_(4)(g)`
`25prop^(2) = 9 , prop = (3)/(5) = 0.6`
`prop = (M_(t) - M_(mix))/((n-1)M_(mix))`
`M_(exp) = (92)/(1 + 0.6) = 57.5 g//mol`