Answer
Equilibrium constant expression:
$$K_c = \frac{[XY]^2}{[X_2][Y_2]}$$
Numerical value:
$$K_c = 36$$
Work Step by Step
1. The formula for the equilibrium constant expression is:
$$K_c = \frac{[Products]}{[Reactants]}$$
Also, the coefficients in the equation are the exponents of the concentrations.
$$K_c = \frac{[XY]^2}{[X_2][Y_2]}$$
2. Count the amount of each molecule in the diagram:
$X_2$: 1 molecule
$Y_2$: 1 molecule
$XY$: 6 molecules
3. Substitute these numbers into the expression, and evaluate it.
$$K_c = \frac{(6)^2}{(1)(1)} = 36$$
