4 mole of SO3 shows dissociation equilibrium in 2 litre flask as :
2SO3⇌2SO2+O2
The equilibrium mixture requires 6.4 mL of 0.1 M acidified KMnO4 for the redox change. Kc for the reaction equilibrium is mol litre −1 is :
a. 0.178
b. 0.356
c. 0.702
d. 0.0178