What is the correct equilibrium constant expression or equation for the reactionH2(g) + Cl2(g) ⇋ 2HCl(g)

1. Problem Breakdown

To write the equilibrium constant expression for the given reaction, we need to identify the reactants and the products involved in the equilibrium process.

2. Relevant Concepts

The equilibrium constant $K_c$ for a reaction is expressed using the concentrations of the products raised to the power of their coefficients divided by the concentrations of the reactants raised to the power of their coefficients. The general formula can be represented as:

$K_c = \frac{[\text{Products}]^{\text{coefficients}}}{[\text{Reactants}]^{\text{coefficients}}}$

3. Analysis and Detail

For the reaction:

$\text{H}_2(g) + \text{Cl}_2(g) \rightleftharpoons 2\text{HCl}(g)$

• Products: $\text{HCl}$ with a coefficient of 2.
• Reactants: $\text{H}_2$ and $\text{Cl}_2$ both with a coefficient of 1.

Thus, the equilibrium constant expression can be written as:

$K_c = \frac{[\text{HCl}]^2}{[\text{H}_2][\text{Cl}_2]}$

4. Verify and Summarize

The expression accurately reflects the stoichiometry of the balanced chemical equation. Each concentration of the products is raised to the power of its coefficient, and the reactants are treated the same way.

Final Answer

The correct equilibrium constant expression for the reaction $\text{H}_2(g) + \text{Cl}_2(g) \rightleftharpoons 2\text{HCl}(g)$ is:

$K_c = \frac{[\text{HCl}]^2}{[\text{H}_2][\text{Cl}_2]}$