Find and fix each mistake in the equilibrium constant expressions. a. 2 H₂S(g) ⇌ 2 H₂(g) + S₂(g) K = [H₂][S₂]/[H₂S]

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1. First, let's understand what the equilibrium constant expression is. The equilibrium constant expression, represented by K, is the ratio of the concentrations of the products to the reactants, each raised to the power of their stoichiometric coefficients in the balanced chemical equation.
2. In the given equation, 2 H2S(g) ⇌ 2 H2(g) + S2(g), the equilibrium constant expression is given as K = [H2][S2]/[H2S].
3. However, this expression is incorrect. The stoichiometric coefficients in the balanced chemical equation should be the powers to which the concentrations of the products and reactants are raised in the equilibrium constant expression.
4. Therefore, the correct equilibrium constant expression for the given equation should be K = [H2]^2[S2]/[H2S]^2.
5. Remember, the equilibrium constant expression is a way to quantify the position of equilibrium for a reaction. It provides a numerical value that indicates whether the reactants or products are favored at equilibrium.

Key Concepts

Equilibrium Constant Expression

The equilibrium constant expression (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a reversible reaction. It is derived from the balanced chemical equation, where the concentrations of gaseous and aqueous species are included, while solids and liquids are omitted. The general form is K = [products]^[coefficients] / [reactants]^[coefficients].

Stoichiometry in Chemical Reactions

Stoichiometry involves the quantitative relationships between the amounts of reactants and products in a chemical reaction, as dictated by the balanced equation. Each species in the reaction is represented by its coefficient, which indicates the proportion in which they react or are produced. Correct stoichiometric coefficients are essential for accurately writing the equilibrium constant expression.

Gaseous Equilibrium and Partial Pressures

In reactions involving gases, the equilibrium constant can also be expressed in terms of partial pressures instead of concentrations. The relationship between concentration and partial pressure is given by the ideal gas law, where pressure is proportional to concentration. For gaseous reactions, Kp is used, and it is related to Kc (the concentration-based equilibrium constant) through the equation Kp = Kc(RT)^(Δn), where Δn is the change in moles of gas.