Write the expression for 𝐾𝑐 for the following reactions. In each case indicate whether the reaction is homogeneous or heterogeneous.
(e) 2Ag(𝑠) + Zn2⁺(𝑎𝑞) ⇌ 2 Ag⁺(𝑎𝑞) + Zn(𝑠)

Verified step by step guidance

1. Identify the reactants and products in the reaction. For the given reaction, the reactants are Ag(s) and Zn2+(aq), and the products are Ag+(aq) and Zn(s).
2. Write the expression for the equilibrium constant, Kc, using the concentrations of the aqueous species. For each species, raise the concentration to the power of its stoichiometric coefficient in the balanced equation.
3. Since Ag(s) and Zn(s) are solids, their activity is considered to be 1 and they do not appear in the expression for Kc.
4. The expression for Kc is therefore: Kc = [Ag+]^2 / [Zn2+]
5. Determine the type of reaction: Since the reaction involves both solid and aqueous species, it is a heterogeneous reaction.

Key Concepts

Equilibrium Constant (Kc)

The equilibrium constant, Kc, is a numerical value that expresses the ratio of the concentrations of products to the concentrations of reactants at equilibrium for a given reaction at a specific temperature. It is calculated using the formula Kc = [products]^[coefficients] / [reactants]^[coefficients]. Understanding Kc is essential for predicting the direction of a reaction and the extent to which reactants are converted to products.

Homogeneous vs. Heterogeneous Reactions

Homogeneous reactions occur when all reactants and products are in the same phase (solid, liquid, or gas), while heterogeneous reactions involve reactants and products in different phases. This distinction is important because it affects how concentrations are expressed in the Kc expression. In heterogeneous reactions, only the concentrations of species in the aqueous or gaseous phase are included in the Kc expression, while solids and liquids are omitted.

Phase Representation in Reactions

In chemical equations, the physical state of each substance is indicated by symbols: (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous solutions. This representation is crucial for determining the correct form of the Kc expression. For example, in the given reaction, only the aqueous ions are included in the Kc expression, as the solid metals do not contribute to the equilibrium concentrations.