Calculating Kc Chemistry

Question

5.0 mol of NOCl is placed an empty 1.0 L container. At equilibrium, 2.0 mol of Cl₂ was found to be in the container. Calculate the value of K_c for this reaction:   2NOCl(g) ⇄ 2NO(g) + Cl₂(g)

Answer 1

2 NOCl(g) <===> 2NO(g) + Cl2(g)......

5.0 .........................0................0............Initial

-2x.......................+2x.............+x............Change

5-2x......................2x..............2.............Equilibrium

From the fact that Cl₂ is 2 @ equilibrium, we know that x = 2. We can now find equilibrium concentrations of NOCl and NO.

[NOCl] = 5 - 2 = 3 M

[NO] = 2 x 2 = 4 M

[Cl₂] = 2 M

Kc = [Cl₂][NO]² / [NOCl]²

Kc = (2)(4)2 / (3)2 = 32/9

Kc = 3.6