Question

Hydrogen cyanide can isomerize to hydrogen isocyanide: HCN(g)= HNC(g)

Delta g f. 75.0. 120.0

A) calculate the equilibrium constant of this reaction at 25.0.

B) if Phcn= 1.000 arm, what is the partial pressure of HNC at equilibrium?

Answer 1

HCN(g) <-------------> HNC(g)

Go = G products - G reactants

= 120 - 75

= 45 kJ/mol

Go = - R T ln Kp

45 = - 8.314 x 10^-3 x 298 x ln Kp

Kp = 1.29 x 10^-8

equilibrium constant = 1.29 x 10^-8

B)

HCN (g) <------------> HNC (g)

1 0

1- x x

Kp = x / 1- x

1.29 x 10^-8 = x / 1 - x

x = 1.29 x 10^-8 atm

partial pressure of P_HNC = 1.29 x 10^-8 atm