What is the equilibrium constant expression (K) for the reaction: 2 H_2(g) + O_2(g) ightleftharpoons 2 H_2O(g)?

• A. K = [H_2O]^2 [O_2] / [H_2]^2
• B. K = [H_2O] / ([H_2][O_2])
• C. K = [H_2O]^2 / ([H_2]^2 [O_2])
• D. K = [H_2]^2 [O_2] / [H_2O]^2

Answer: (C)

Verified step by step guidance

1. Identify the balanced chemical equation: \$2 \mathrm{H}_2(g) + \mathrm{O}_2(g) \rightleftharpoons 2 \mathrm{H}_2\mathrm{O}(g)$.
2. Recall that the equilibrium constant expression \(K\) is written as the ratio of the concentrations of products to reactants, each raised to the power of their stoichiometric coefficients.
3. Write the general form: \(K = \frac{[\text{products}]^{\text{coefficients}}}{[\text{reactants}]^{\text{coefficients}}}\).
4. Apply this to the reaction: the product is \(\mathrm{H}_2\mathrm{O}\) with coefficient 2, and the reactants are \(\mathrm{H}_2\) with coefficient 2 and \(\mathrm{O}_2\) with coefficient 1, so \(K = \frac{[\mathrm{H}_2\mathrm{O}]^{2}}{[\mathrm{H}_2]^{2} [\mathrm{O}_2]}\).
5. Confirm that the equilibrium constant expression includes the correct species and their exponents matching the balanced equation.