Kp for the reaction is 9 at 7 atm and 300K A2(g)=B2(g)+C2(g) calculate average molar mass at equilibrium of mixture . (given : molar mass of A2=70 of B2=49 C2=21) ...pls pls pls answer fast

The relation between Kp​ and Kc​ is Kp​=Kc​(RT)Δn=Kc​^(RT) because Δn=1

9=Kc​×0.0821×300
Kc​=0.3654
Let the equilibrium number of moles  (and molar concentration) of A,B and C be 1,x and x respectively.
Kc​=[C][A][B]​=1X2​=0.3654
x=0.6044
Thus equilibrium moles of A,B and C are 1,0.6 and 0.6 respectively.
The mole fractions of A,B and C are 0.455, 0.27 and 0.27 respectively.
Average molecular weight =70×0.455+49×0.27+21×0.27=50