At a certain temperature, 0.820mol SO₃ is placed in a 3.50L container. 2SO₃(g) ⇌ 2SO₂(g) + O₂(g) At equilibrium, 0.200mol O₂ is present. Calculate Kc.
a) 1.08
b) 1.20
c) 1.38
d) 1.50