The given chemical reaction is:

[COCl_2(g) \rightleftharpoons CO(g) + Cl_2(g) \quad K = 1.5 \times 10^{10}]

We need to write the expression for the equilibrium constant ((K)) for this reaction.
Are the reactants or products favored at equilibrium? Select the single best answer.

products

neither

reactants

The expression for the equilibrium constant (K) for this reaction is:

\[K = \dfrac{[CO][Cl_2]}{[COCl_2]}\]

Because the equilibrium constant (K) is very large (1.5 x 10^10), it indicates that at equilibrium, the products (CO and Cl2) are favored over the reactant (COCl2).

Therefore, the correct answer is: products