For the reaction SnO2(s)+2H2(g)⇌2H2O(g)+Sn(l)  at 900 K, the equilibrium steam-hydrogen mixture was found to be 40% H2 by volume. The Kp  is

SnO2(s)+2H2(g)⇌2H2O(g)+Sn(l)              40%=0.4            0.6                     (∵X1+X2=1)               Kp=0.6×0.60.4×0.4                      =3×32×2                      =94                      =2.25