For each of the following equilibria, write the equilibrium constant expression for Kc. (a) 2 C2H4(g) + O2(g) ⇌ 2 CH3CHO(g) (b) CO(g) + H2O(g) ⇌ CO2(g) + H2(g) (c) 4 NH3(g) + 5 O2(g) ⇌ 4 NO(g) + 6 H2O(g)

Verified step by step guidance

Step 1: Understand that the equilibrium constant expression, Kc, is written as the ratio of the concentrations of the products to the concentrations of the reactants, each raised to the power of their respective coefficients in the balanced chemical equation.

Step 2: For reaction (a) 2 C2H4(g) + O2(g) ⇌ 2 CH3CHO(g), write the Kc expression as: Kc = [CH3CHO]^2 / ([C2H4]^2 * [O2]).

Step 3: For reaction (b) CO(g) + H2O(g) ⇌ CO2(g) + H2(g), write the Kc expression as: Kc = [CO2][H2] / ([CO][H2O]).

Step 4: For reaction (c) 4 NH3(g) + 5 O2(g) ⇌ 4 NO(g) + 6 H2O(g), write the Kc expression as: Kc = [NO]^4 * [H2O]^6 / ([NH3]^4 * [O2]^5).

Step 5: Remember that the concentrations are typically expressed in molarity (moles per liter) and that the equilibrium constant is dimensionless.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

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 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 involved remain unchanged, allowing for the calculation of Kc.

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 at equilibrium.

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Equilibrium Constant Expressions

Related Practice

Textbook Question

Identify the true statement about the rate of the forward and reverse reaction once a reaction has reached equilibrium. (a) The rate of the forward reaction and the reverse reaction is zero. (b) The rate of the forward reaction is greater than the rate of the reverse reaction. (c) The rate of the reverse reaction is greater than the rate of the forward reaction. (d) The rate of the forward reaction is equal to the rate of the reverse reaction.

Textbook Question

For each of the equilibria in Problem 15.56, write the equi-librium constant expression for Kp and give the equation that relates Kp and Kc. (a)

Textbook Question

The reaction 2 AsH31g2 ∆ As21g2 + 3 H21g2 has Kp = 7.2 * 107 at 1073 K. At the same temperature, what is Kp for each of the following reactions? (a) As21g2 + 3 H21g2 ∆ 2 AsH31g2