Identify the true statement about the concentrations of A and B once the reaction A ⇌ B has reached equilibrium. (a) The concentration of A equals the concentration of B. (b) The concentrations of A and B are constant. (c) The concentration of A decreases and the concentration of B increases. (d) The concentration of B decreases and the concentration of A increases.

Name: Chemistry
Author: McMurry
ISBN: 9781292336145

Verified step by step guidance

Step 1: Understand the concept of chemical equilibrium. At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction, meaning the concentrations of reactants and products remain constant over time.

Step 2: Analyze each statement in the context of equilibrium. Statement (a) suggests that the concentrations of A and B are equal, which is not necessarily true at equilibrium unless the equilibrium constant dictates it.

Step 3: Evaluate statement (b). At equilibrium, the concentrations of A and B are indeed constant, as the rates of the forward and reverse reactions are equal.

Step 4: Consider statement (c). This describes a scenario where the reaction is still proceeding towards equilibrium, not a state of equilibrium itself.

Step 5: Assess statement (d). Similar to statement (c), this describes a non-equilibrium state where the reaction is still shifting towards equilibrium.

Key Concepts

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

Chemical Equilibrium

Chemical equilibrium occurs in a reversible reaction when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. At this point, the system is in a dynamic state where the concentrations do not change over time, even though both reactions continue to occur.

Concentration in Equilibrium

At equilibrium, the concentrations of reactants and products remain constant, but they do not have to be equal. This means that while the amounts of A and B may differ, their concentrations will stabilize at specific values determined by the reaction conditions and the equilibrium constant.

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. This principle helps predict how the concentrations of A and B will respond to external changes, but it does not imply that their concentrations will be equal.

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Textbook Question

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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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