Skip to main content
Pearson+ LogoPearson+ Logo
Ch.15 - Chemical Equilibrium
All textbooksMcMurry 8th EditionCh.15 - Chemical EquilibriumProblem 7
Chapter 15, Problem 7

The gas-phase reaction 2 SO2(g) + O2(g) ⇌ 2 SO3(g) has an equilibrium constant Kc = 5.8 * 10^3 at 600 °C. A mixture contains [SO2] = 0.10 M, [O2] = 0.100 M, and [SO3] = 0.200 M. Which statement is true about the reaction direction and equilibrium mixture? (LO 15.8, 15.9) (a) The mixture is at equilibrium and contains appreciable amounts of reactants and products. (b) The reaction will shift to make more product, and the equilibrium mixture contains appreciable amounts of reactants and products. (c) The reaction will shift to make more reactants, and the equilibrium mixture contains mostly product. (d) The reaction will shift to make more product, and the equilibrium mixture contains mostly reactant.

Verified step by step guidance
1
Calculate the reaction quotient, Qc, using the initial concentrations: Qc = \frac{[SO_3]^2}{[SO_2]^2[O_2]}.
Substitute the given concentrations into the expression for Qc: [SO_2] = 0.10 \text{ M}, [O_2] = 0.100 \text{ M}, [SO_3] = 0.200 \text{ M}.
Compare the calculated Qc value to the given equilibrium constant Kc = 5.8 \times 10^3.
Determine the direction of the reaction: if Qc < Kc, the reaction will shift to the right (toward products); if Qc > Kc, the reaction will shift to the left (toward reactants).
Based on the comparison, choose the correct statement about the reaction direction and equilibrium mixture.

Key Concepts

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

Chemical Equilibrium

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. In this state, the system is dynamic, meaning that reactions continue to occur, but there is no net change in the concentrations. Understanding this concept is crucial for analyzing how changes in concentration, temperature, or pressure can affect the position of equilibrium.
Recommended video:
Guided course
04:21
Chemical Equilibrium Concepts

Equilibrium Constant (Kc)

The equilibrium constant (Kc) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. For the reaction 2 SO2(g) + O2(g) ⇌ 2 SO3(g), Kc = [SO3]^2 / ([SO2]^2[O2]). A large Kc value, such as 5.8 * 10^3, indicates that at equilibrium, the concentration of products is significantly higher than that of reactants, suggesting a tendency for the reaction to favor product formation.
Recommended video:
Guided course
03:20
Equilibrium Constant Expressions

Le Chatelier's Principle

Le Chatelier's Principle states that if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will adjust to counteract that change and restore a new equilibrium. In the context of the given reaction, if the concentration of reactants or products changes, the reaction will shift in the direction that reduces the effect of that change, helping to predict the direction of the shift and the composition of the equilibrium mixture.
Recommended video:
Guided course
07:32
Le Chatelier's Principle
Related Practice
Textbook Question
The reaction A21g2 + B21g2 ∆ 2 AB1g2 has an equilib- rium constant Kc = 9. The following figure represents areaction mixture that contains A2 molecules (red), B2 mol- ecules (blue), and AB molecules. What statement about the mixture is true? (LO 15.5)

(a) The mixture is at equilibrium, and there will be no net shift in reaction direction.(b) The reaction will shift toward the reactants to reach equilibrium.(c) The reaction will shift toward the products to reach equilibrium.(d) More information is needed to answer this question.
1
views