Question

Consider the reaction between NO and Cl2 to form NOCl: 2NO(g)+Cl2(g)⇌2NOCl(g) A reaction mixture at a certain temperature initially contains only [NO]= 0.50 M and [Cl2]= 0.55. After the reaction comes to equilibrium, the concentration of NOCl is 0.35 M .

Part A

Find the value of the equilibrium constant (Kc) at this temperature.

Express your answer using two significant figures.

Kc=???

Answer 1

Answer – We are given, [NO] = 0.50 M, [Cl₂] = 0.55 M ,

At equilibrium, [NOCl] = 0.35 M

We need to put ICE chart –

     2NO(g) + Cl₂(g) -----> 2NOCl

I   0.50          0.55             0

C   -2x           -x             +2x

E 0.50-2x   0.55-x         0.35

We know, at equilibrium , [NOCl] = 2x = 0.35 M

So, x = 0.35/2 = 0.175 M

[NO] = 0.50-2x

          = 0.50 -0.35

          = 0.15 M

[Cl₂] = 0.55-x

          = 0.55- 0.175

        = 0.375 M

So, Kc =[NOCl]² /[NO]²[Cl₂]

           = (0.35)² / (0.15)²*(0.375)

            = 15

So, the equilibrium constant (Kc) at this temperature is 15