Ch.15 - Chemical Equilibrium

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.15 - Chemical Equilibrium

Problem 49

Chapter 15, Problem 49

The following picture represents the equilibrium state for the reaction 2 AB ∆ A2 + B2. Which rate constant is larger, kf or kr? Explain.

Verified step by step guidance

Step 1: Understand the reaction dynamics. The reaction given is 2 AB \rightleftharpoons A_2 + B_2, which is a reversible reaction. This means it can proceed in both the forward direction (formation of A_2 and B_2) and the reverse direction (formation of AB from A_2 and B_2).

Step 2: Define the rate constants. In a reversible reaction, k_f is the rate constant for the forward reaction (2 AB \rightarrow A_2 + B_2), and k_r is the rate constant for the reverse reaction (A_2 + B_2 \rightarrow 2 AB).

Step 3: Consider the equilibrium state. At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction. This means that the concentrations of reactants and products remain constant over time.

Step 4: Analyze the equilibrium constant expression. The equilibrium constant (K_eq) is given by the ratio of the rate constants: K_eq = \frac{k_f}{k_r}. If K_eq > 1, the forward reaction is favored, indicating k_f > k_r. If K_eq < 1, the reverse reaction is favored, indicating k_r > k_f.

Step 5: Use the picture to determine K_eq. If the picture shows more products (A_2 and B_2) than reactants (AB), then K_eq > 1, suggesting k_f > k_r. Conversely, if there are more reactants than products, then K_eq < 1, suggesting k_r > k_f.

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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 of the substances involved.

Rate Constants (kf and kr)

Rate constants, denoted as kf for the forward reaction and kr for the reverse reaction, are specific to each reaction at a given temperature. The magnitude of these constants indicates the speed of the respective reactions; a larger kf suggests a faster forward reaction, while a larger kr indicates a faster reverse reaction.

Le Chatelier's Principle

Le Chatelier's Principle states that if a system at equilibrium is disturbed, the system will adjust to counteract the disturbance and restore a new equilibrium. This principle helps predict how changes in concentration, pressure, or temperature will affect the position of equilibrium and the relative rates of the forward and reverse reactions.

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Related Practice

Textbook Question

Consider the reaction A + B ∆ AB. The vessel on the right contains an equilibrium mixture of A molecules (red spheres), B molecules (blue spheres), and AB molecules. If the stopcock is opened and the contents of the two vessels are allowed to mix, will the reaction go in the forward or reverse direction? Explain.

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Textbook Question

The following pictures represent the composition of the equi- librium mixture for the reaction A + B ∆ AB at 300 K and at 400 K.

Is the reaction exothermic or endothermic? Explain using Le Châtelier's principle.

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Textbook Question

The following picture represents the composition of the equi- librium mixture for the endothermic reaction A2 ∆ 2 A at 500 K. Draw a picture that represents the equilibrium mixture after each of the following changes.(b) Increasing the volume

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Textbook Question

The following pictures represent the initial and equilibrium states for the exothermic decomposition of gaseous A mol- ecules (red) to give gaseous B molecules (blue).(b) Will the number of A molecules in the equilibrium mix- ture increase, decrease, or remain the same after each of the following changes? Explain.(3) Increasing the pressure by adding an inert gas

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Textbook Question

The following pictures represent the initial and equilibrium states for the exothermic decomposition of gaseous A mol- ecules (red) to give gaseous B molecules (blue). (a) Write a balanced chemical equation for the reaction.

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Textbook Question

The following pictures represent the initial and equilibrium states for the exothermic reaction of solid A (red) with gas- eous B2 (blue) to give gaseous AB. (a) Write a balanced chemical equation for the reaction.

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