What is the expression for the equilibrium constant (K) for the reaction: Li(s) + 2H2O(l) ⇌ Li+(aq) + 2OH-(aq) + H2(g)?

• A. K = [Li+][OH-]^2/[H2]
• B. K = [Li+][OH-]^2
• C. K = [Li+][OH-]^2[H2]/[H2O]^2
• D. K = [Li+][OH-]^2[H2]

Answer: (B)

Verified step by step guidance

1. Identify the type of equilibrium constant expression needed for the reaction. Since the reaction involves aqueous ions and gases, we are dealing with the equilibrium constant for concentrations, Kc.
2. Write the balanced chemical equation for the reaction: Li(s) + 2H2O(l) ⇌ Li+(aq) + 2OH-(aq) + H2(g).
3. Determine which species are included in the equilibrium expression. Only aqueous and gaseous species are included, while pure solids and liquids are omitted.
4. Construct the equilibrium expression using the concentrations of the products over the reactants. Since Li(s) and H2O(l) are pure substances, they are not included in the expression.
5. The equilibrium expression is: Kc = $\frac{{\mathrm{[Li]}}_{+}{\mathrm{[OH]}}_{-}^2}{{\mathrm{[H]}}_2}$. This expression includes the concentrations of Li+, OH-, and H2.