Write the equilibrium constant expressions for the following reactions.
d. C(s) + H₂O(g) ⇌ CO(g) + H₂(g)

Verified step by step guidance

1. Identify the general form of the equilibrium constant expression, which is written as K = [products] / [reactants]. Concentrations of gases are expressed in terms of partial pressures or molar concentrations, while pure solids and liquids are not included in the expression.
2. Recognize that in the given reaction, C(s) is a solid. Since the equilibrium constant expression does not include pure solids, C(s) will not appear in the expression.
3. List the gaseous species in the reaction: H2O(g), CO(g), and H2(g). These are the species that will be included in the equilibrium constant expression.
4. Write the equilibrium constant expression as follows: K = ([CO][H2]) / [H2O], where [CO], [H2], and [H2O] represent the molar concentrations (or partial pressures) of the respective gases at equilibrium.
5. Ensure that the expression is balanced and reflects the stoichiometry of the reaction. In this case, all coefficients are 1, so no exponents are needed in the equilibrium constant expression.

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 indicates the extent to which reactants are converted into products. A larger K value suggests a greater concentration of products at equilibrium, while a smaller K indicates a higher concentration of reactants.

Reaction Quotient (Q)

The reaction quotient (Q) is a measure of the relative concentrations of products and reactants at any point in time during a reaction. 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: if Q < K, the reaction shifts right to produce more products; if Q > K, it shifts left to produce more reactants.

Gaseous and Solid Reactants in K Expressions

In equilibrium constant expressions, only the concentrations of gaseous and aqueous species are included, while solids and pure liquids are omitted. This is because the activity of solids is considered constant and does not affect the equilibrium position. For the given reaction, only the gaseous products (CO and H2) and the gaseous reactant (H2O) will be included in the equilibrium expression, while the solid carbon (C) will not.