For each of the following equilibria, write the equilibrium constant expression for Kc. (a) CH4(g) + H2O(g) ⇌ CO(g) + 3 H2(g) (b) 3 F2(g) + Cl2(g) ⇌ 2 ClF3(g) (c) H2(g) + F2(g) ⇌ 2 HF(g)

Verified step by step guidance

1. Step 1: Understand the concept of equilibrium constant (Kc). The equilibrium constant expression for a reaction is derived from the balanced chemical equation and is a ratio of the concentrations of products to reactants, each raised to the power of their respective coefficients in the balanced equation.
2. Step 2: For reaction (a) CH4(g) + H2O(g) ⇌ CO(g) + 3 H2(g), write the equilibrium constant expression Kc = [CO][H2]^3 / [CH4][H2O].
3. Step 3: For reaction (b) 3 F2(g) + Cl2(g) ⇌ 2 ClF3(g), write the equilibrium constant expression Kc = [ClF3]^2 / [F2]^3[Cl2].
4. Step 4: For reaction (c) H2(g) + F2(g) ⇌ 2 HF(g), write the equilibrium constant expression Kc = [HF]^2 / [H2][F2].
5. Step 5: Remember that the concentrations are typically expressed in molarity (moles per liter) and that the equilibrium constant is dimensionless.

Key Concepts

Equilibrium Constant (Kc)

The equilibrium constant, Kc, is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given chemical reaction. It is calculated using the formula Kc = [products]^[coefficients] / [reactants]^[coefficients], where the brackets denote molarity and the coefficients are the stoichiometric coefficients from the balanced equation.

Chemical Equilibrium

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products over time. At this point, the system is in a state of balance, and the concentrations of all species remain unchanged unless disturbed by external factors, such as changes in temperature or pressure.

Stoichiometry in Equilibrium Expressions

Stoichiometry refers to the relationship between the quantities of reactants and products in a chemical reaction. In equilibrium expressions, the coefficients from the balanced chemical equation are used as exponents in the Kc expression, reflecting the proportionality of the concentrations of each species involved in the reaction at equilibrium.