Answer
a. $$K_c = \frac{[ SO_3 ]^{ 2 }}{[ SO_2 ]^{ 2 }[ O_2 ]}$$
b. $K_c = 3.0 \times 10^2$
Work Step by Step
1. Write the equilibrium constant expression:
$$K_c = \frac{[Products]}{[Reactants]} = \frac{[ SO_3 ]^{ 2 }}{[ SO_2 ]^{ 2 }[ O_2 ]}$$
2. Substitute the values and calculate the constant value:
$$K_c = \frac{( 0.60 )^{ 2 }}{( 0.10 )^{ 2 }( 0.12 )} = 3.0 \times 10^2$$
