When 0.40 mole of SO2 and 0.60 mole of O2 are placed in an evacuated 1.00-liter flask, the reaction represented above occurs. After the reactants and the product reach equilibrium and the initial temperature is restored, the flask is found to contain 0.30 mole of SO3. Based on these results, the equilibrium constant, Kc for the reaction is.

kc = 20

Explanation:

The reaction is:

2SO₂ + O₂ ⇄ 2SO₃

Where kc is defined as:

kc = SO₃² / O₂×SO₂² (1)

The initial moles are 0,40 for SO₂ and 0,60 moles for O₂

The moles in equilibrium must be:

SO₂: 0,40 - 2x

O₂: 0,60 - x

SO₃: 2x = 0,30; x = 0,15

Replacing:

SO₂: 0,40 - 2×0,15 = 0,10 moles

O₂: 0,60 - 0,15 = 0,45 moles

Replacing these values in (1):

kc = 0,30² / 0,45×0,10²

kc = 20

I hope it helps!