The all substances that participate in the
reaction are in gaseous phase and the given data are the concentrations when
the reaction at equilibrium. Hence, we can use that given concentrations directly to find out the equilibrium constant, Kc.
The balanced equation for the equilibrium is,
2SO₂(g) + O₂(g) ⇄ 2SO₃(g)
Kc = [SO₃(g)]² / [SO₂(g)]² [O₂(g)]
Kc = (4 mol/L)² / (2 mol/L)² (1 mol/L)
Kc = 4 mol⁻¹ L
Hence, the equilibrium constant is 4 mol⁻¹ L
