Write the equilibrium constant expressions for the following reactions:
a. 2 CO(g) + O₂(g) ⇌ 2 CO₂(g)

Verified step by step guidance

1. Identify the general form of the equilibrium constant expression (Kc) for a chemical reaction. It is written as the ratio of the concentrations of the products raised to their stoichiometric coefficients to the concentrations of the reactants raised to their stoichiometric coefficients.
2. Write the equilibrium constant expression for the given reaction: \( 2 \text{CO}(g) + \text{O}_2(g) \rightleftharpoons 2 \text{CO}_2(g) \). The general form is \( K_c = \frac{[\text{products}]^{\text{coefficients}}}{[\text{reactants}]^{\text{coefficients}}} \).
3. Substitute the chemical species into the expression. The product is \( \text{CO}_2(g) \), and the reactants are \( \text{CO}(g) \) and \( \text{O}_2(g) \).
4. Raise the concentration of each species to the power of its stoichiometric coefficient. For \( \text{CO}_2(g) \), the coefficient is 2, so it becomes \( [\text{CO}_2]^2 \). For \( \text{CO}(g) \), the coefficient is 2, so it becomes \( [\text{CO}]^2 \). For \( \text{O}_2(g) \), the coefficient is 1, so it remains \( [\text{O}_2] \).
5. Combine these into the final equilibrium constant expression: \( K_c = \frac{[\text{CO}_2]^2}{[\text{CO}]^2[\text{O}_2]} \).

Key Concepts

Equilibrium Constant (K)

The equilibrium constant (K) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given chemical reaction. It is specific to a particular reaction at a specific temperature. A large K value indicates that products are favored at equilibrium, while a small K value suggests that reactants are favored.

Reaction Quotient (Q)

The reaction quotient (Q) is a measure of the relative amounts of products and reactants present in a reaction at any point in time. It is calculated using the same formula as the equilibrium constant but with the current concentrations. Comparing Q to K helps determine the direction in which a reaction will proceed to reach equilibrium.

Stoichiometry in Equilibrium Expressions

Stoichiometry refers to the coefficients of reactants and products in a balanced chemical equation, which are used to formulate the equilibrium constant expression. For the reaction 2 CO(g) + O2(g) ⇌ 2 CO2(g), the equilibrium expression is K = [CO2]^2 / ([CO]^2[O2]), where the concentrations are raised to the power of their respective coefficients, reflecting their proportions in the reaction.