When this equilibrium shifts to the right, forming "X" mol of O2
2SO3(g) ---> 2SO2(g) + O2(g)
0.660 - 2X --> --> 2X & X
since X = 0.130
this becomes
0.400 <=> 0.260 & 0.130
find moles / litre:
(0.400) / 4.5L --> --> 0.260 / 4.5L & 0.130 / 4.5 L
which gives these molarities:
2SO3(g) ---> 2SO2(g) + 1 O2(g)
[0.08889] --> [0.05778] & [0.02889]
Kc = [SO2]^2 [O2] / [SO3]^2
Kc = [0.05778]^2 [0.02889] / [0.08889]^2
Kc = (0.003338) [0.02889] / [(0.007901)
Kc = 0.0122