Ch.15 - Chemical Equilibrium

Brown - Chemistry: The Central Science 15th Edition

Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook

Brown 15th Edition

Ch.15 - Chemical Equilibrium

Problem 10a

Chapter 15, Problem 10a

The diagram shown here represents the equilibrium state for the reaction A2(𝑔) + 2B(𝑔) ⇌ 2AB(𝑔). (a) Assuming the volume is 2 L, calculate the equilibrium constant 𝐾𝑐 for the reaction.

Verified step by step guidance

Step 1: Identify the equilibrium concentrations of the reactants and products from the diagram. The number of molecules of each species in the diagram represents the number of moles of that species. Divide the number of moles by the volume (2 L) to get the molar concentration.

Step 2: Write the expression for the equilibrium constant, Kc, for the reaction. For the reaction A2(g) + 2B(g) ⇌ 2AB(g), the equilibrium constant expression is Kc = [AB]^2 / ([A2][B]^2).

Step 3: Substitute the equilibrium concentrations from Step 1 into the equilibrium constant expression from Step 2. Remember that the concentrations should be in moles per liter (M).

Step 4: Perform the calculations as indicated in the equilibrium constant expression. Remember to square the concentration of AB and B as indicated in the equilibrium constant expression.

Step 5: The result of these calculations is the equilibrium constant, Kc, for the reaction. This value indicates the extent to which the reaction proceeds to the right (towards the products) at equilibrium.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

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 reactants at equilibrium for a given reaction at a specific temperature. It is calculated using the formula Kc = [products]^[coefficients] / [reactants]^[coefficients]. A Kc value greater than 1 indicates that products are favored at equilibrium, while a value less than 1 suggests that reactants are favored.

Concentration

Concentration refers to the amount of a substance (solute) present in a given volume of solution. It is typically expressed in moles per liter (Molarity, M). In equilibrium calculations, the concentrations of the reactants and products at equilibrium are essential for determining the value of Kc, as they directly influence the ratio used in the equilibrium expression.

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It involves using the coefficients from the balanced chemical equation to relate the amounts of substances consumed and produced. In the context of equilibrium, stoichiometry is crucial for determining the concentrations of reactants and products based on their initial amounts and the changes that occur as the system reaches equilibrium.

Recommended video:

Guided course

01:16

Stoichiometry Concept

Related Practice

Textbook Question

The equilibrium constant for the dissociation of molecular iodine, I₂(g) ⇌ 2 I(g), at 800 K is K_c = 3.1 × 10^–5. (a) Which species predominates at equilibrium I₂ or I?

Textbook Question

The reaction A₂ + B₂ ⇌ 2 AB has an equilibrium constant K_c = 1.5. The following diagrams represent reaction mixtures containing A₂ molecules (red), B₂ molecules (blue), and AB molecules. (a) Which reaction mixture is at equilibrium?

views

Textbook Question

The equilibrium constant for the dissociation of molecular iodine, I₂(g) ⇌ 2 I(g), at 800 K is K_c= 3.1×10⁻⁵. (b) Assuming both forward and reverse reactions are elementary reactions, which reaction has the larger rate constant, the forward or the reverse reaction?

views

Textbook Question

When lead(IV) oxide is heated above 300°C, it decomposes according to the reaction, 2 PbO₂(𝑠)⇌2PbO(𝑠)+O2(𝑔). Consider the two sealed vessels of PbO₂ shown here. If both vessels are heated to 400°C and allowed to come to equilibrium, which of the following statements is or are true? c. The partial pressure of O2(𝑔) will be the same in vessels A and B. [Section 15.4]

Textbook Question

b. The solid left at the bottom of each vessel will be a mixture of PbO₂(𝑠) and PbO(𝑠).

Textbook Question

Suppose that the gas-phase reactions A → B and B → A are both elementary reactions with rate constants of 4.7×10⁻³ s⁻¹ and 5.8×10⁻¹ s⁻¹, respectively. (a) What is the value of the equilibrium constant for the equilibrium A(g) ⇌ B(g)? (b) Which is greater at equilibrium, the partial pressure of A or the partial pressure of B?