Question

1.72 moles of NOCI were placed in a 2.50 L reaction chamber
at 427°C. After equilibrium was reached, 1.16 moles of NOCI
remained. Calculate the equilibrium constant, K., for the
reaction
2NOCI(g) = 2NO(g) + Cl2(g).

Answer 1

The equilibrium constant, Kc=0.026

Further explanation

Given

1.72 moles of NOCI

1.16 moles of NOCI  remained

2.50 L reaction chamber

Reaction

2NOCI(g) = 2NO(g) + Cl2(g).

Required

the equilibrium constant, Kc

Solution

ICE method

   2NOCI(g) = 2NO(g) + Cl2(g).

I    1.72

C   0.56           0.56         0.28

E   1.16              0.56         0.28

Molarity at equilibrium :

NOCl :

$\tt \dfrac{1.16}{2.5}=0.464$

NO :

$\tt \dfrac{0.56}{2.5}=0.224$

Cl2 :

$\tt \dfrac{0.28}{2.5}=0.112$

$\tt Kc=\dfrac{[NO]^2[Cl_2]}{[NOCl]^2}\\\\Kc=\dfrac{0.224^2\times 0.112}{0.464^2}=0.026$