Ch.15 - Chemical Equilibrium

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McMurry 8th Edition

Ch.15 - Chemical Equilibrium

Problem 43

Chapter 15, Problem 43

The reaction A2 + B ∆ A + AB has an equilibrium con-stant Kc = 2. The following pictures represent reaction mix- tures that contain A atoms (red), B atoms (blue), and A2 and AB molecules.
(a) Which reaction mixture is at equilibrium?

Verified step by step guidance

Step 1: Identify the number of A2, B, A, and AB molecules in each reaction mixture.

Step 2: Calculate the concentration of each species in each mixture. Assume the volume is constant and the same for all mixtures.

Step 3: Use the equilibrium constant expression for the reaction, Kc = [A][AB] / [A2][B], to calculate the equilibrium constant for each mixture.

Step 4: Compare the calculated equilibrium constant for each mixture with the given Kc value of 2.

Step 5: Determine which mixture has a calculated equilibrium constant closest to 2, indicating it is at equilibrium.

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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 over time. In this state, the system appears static, but molecular activity continues. Understanding equilibrium is crucial for analyzing reaction mixtures and determining which mixture is at equilibrium.

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 A2 + B ⇌ A + AB, Kc = [A][AB]/[A2][B]. A Kc value of 2 indicates that at equilibrium, the concentration of products is twice that of the reactants, guiding the analysis of the reaction mixtures.

Molecular Representation

Molecular representation visually depicts the composition of a reaction mixture, showing the types and quantities of molecules present. In the provided images, red spheres represent A atoms, blue spheres represent B atoms, and the combinations represent A2 and AB molecules. Analyzing these representations helps identify which mixture aligns with the equilibrium condition based on the Kc value.

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Related Practice

Textbook Question

If K_c = 7.5×10⁻⁹ at 1000 K for the reaction N₂(g) + O₂(g) → 2 NO(g), give the value of K_c at 1000 K for the reaction

(b) NO(g) → 1/2 N₂(g) + 1/2 O₂(g)

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?

Textbook Question

Consider the interconversion of A molecules (red spheres) and B molecules (blue spheres) according to the reaction A ∆ B. Each of the series of pictures at the right represents a separate experiment in which time increases from left to right:(b) What is the value of the equilibrium constant Kc for the reaction A ∆ B?

Textbook Question

The following pictures represent the initial state and the equilibrium state for the reaction of A₂ molecules (red) with B atoms (blue) to give AB molecules. (a) Write a balanced chemical equation for the reaction.

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.

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.

The reaction A2 + B ∆ A + AB has an equilibrium con-stant Kc = 2. The following pictures represent reaction mix- tures that contain A atoms (red), B atoms (blue), and A2 and AB molecules. (a) Which reaction mixture is at equilibrium?

Verified video answer for a similar problem:

Key Concepts

Chemical Equilibrium

Equilibrium Constant (Kc)

Molecular Representation

The reaction A2 + B ∆ A + AB has an equilibrium con-stant Kc = 2. The following pictures represent reaction mix- tures that contain A atoms (red), B atoms (blue), and A2 and AB molecules.
(a) Which reaction mixture is at equilibrium?