Answer
The diagram that represents the molecules of this reaction at equilibrium is B.
Work Step by Step
1. Calculate $K_c$ for each diagram.
$$K_c = \frac{[Products]}{[Reactants]} = \frac{[XY]^2}{[X_2][Y_2]}$$
A: 1 $X_2$, 1 $Y_2$ and 6 $XY$
$$K_c = \frac{(6)^2}{(1)(1)} = 36$$
B: 2 $X_2$, 2 $Y_2$ and 4 $XY$:
$$K_c = \frac{(4)^2}{(2)(2)} = 4$$
C: 3 $X_2$, 3 $Y_2$ and 2 $XY$:
$$K_c = \frac{(2)^2}{(3)(3)} = 0.44$$
2. Therefore, the diagram that represents the molecules of this reaction at equilibrium is B.
