At a certain temperature, 0.920 mol SO3 is placed in a 2.00 L container.

Question

2SO3(g)↽−−⇀2SO2(g)+O2(g)At equilibrium, 0.120 mol O2

is present. Calculate 𝐾c.

Answer 1

[SO3] = 0.920 mol/2 L = 0.46 M

2SO₃(g) <==> 2SO₂(g) + O₂(g)

0.46.................0...............0.........Initial

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

0.46-2x...........2x..............x.........Equilibrium

Since we are told that [O2] = 0.120 mol/2 L = 0.06 M, this is = to x

Equilibrium concentrations are as follows:

[SO3] = 0.46 - 0.12 = 0.34 M

[SO2] = 2 x 0.06 M = 0.12 M

[O2] = 0.06 M

Kc = [SO₂]²[O₂] / [SO₃]²

Kc = (0.12)²(0.06) / (0.34)²

Kc = 7.5x10^-3