Write an expression for the equilibrium constant of each chemical equation.
a. SbCl₅(g) ⇌ SbCl₃(g) + Cl₂(g)
b.2 BrNO(g) ⇌ 2 NO(g) + Br₂(g)
c. CH₄(g) + 2 H₂S(g) ⇌ CS₂(g) + 4 H₂(g)
d. 2 CO(g) + O₂(g) ⇌ 2 CO₂(g)

Verified step by step guidance

1. Step 1: Understand the concept of the equilibrium constant (K). The equilibrium constant is a measure of the ratio of the concentrations of products to reactants at equilibrium, with each concentration raised to the power of its stoichiometric coefficient in the balanced chemical equation.
2. Step 2: Identify the reactants and products in the given chemical equation. In the equation SbCl5(g) ⇌ SbCl3(g) + Cl2(g), SbCl5(g) is the reactant and SbCl3(g) and Cl2(g) are the products.
3. Step 3: Write the general form of the equilibrium constant expression. For a general reaction aA + bB ⇌ cC + dD, the equilibrium constant expression is K = ([C]^c [D]^d) / ([A]^a [B]^b), where [A], [B], [C], and [D] represent the molar concentrations of the species at equilibrium.
4. Step 4: Substitute the reactants and products into the equilibrium constant expression. For the given reaction, the equilibrium constant expression is K = ([SbCl3] [Cl2]) / [SbCl5].
5. Step 5: Note that the stoichiometric coefficients in the balanced chemical equation become the powers to which the concentrations are raised in the equilibrium constant expression. In this case, all coefficients are 1, so the concentrations are raised to the power of 1.

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 certain temperature and provides insight into the extent to which a reaction proceeds. A larger K value indicates a greater concentration of products at equilibrium, while a smaller K suggests that reactants are favored.

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 no net change is observed. Understanding this concept is crucial for writing equilibrium expressions, as it highlights the dynamic nature of reactions.

Writing Equilibrium Expressions

To write an equilibrium expression for a chemical reaction, the general form is K = [products]^coefficients / [reactants]^coefficients, where the brackets denote the molar concentrations of the species involved. For the reaction given, SbCl5(g) ∆ SbCl3(g) + Cl2(g), the equilibrium expression would be K = [SbCl3][Cl2] / [SbCl5]. This expression reflects the relationship between the concentrations of the reactants and products at equilibrium.