Equilibrium Foundations

Learn the models, terms, and applications of equilibrium foundations.

Lesson 3 of 32 parts Practice Flashcards

1/2

Concepts and Models

Objective: Explain the concepts and assumptions used in equilibrium foundations.

At dynamic equilibrium, forward and reverse reaction rates are equal while microscopic reactions continue. Concentrations need not be equal. Equilibrium expressions reflect balanced coefficients and use activities; introductory dilute-solution problems approximate them with concentration ratios and omit pure solids and liquids. Compare Q with K at the same temperature: Q<K favors net forward change, Q>K favors reverse change. A catalyst does not change K. Numerical concentration ratios here use the classroom convention and should not be mistaken for a full thermodynamic treatment.

Formulas

Kc≈product concentration factors/reactant concentration factors
Q<K: net forward; Q>K: net reverse

Worked examples

Try itFor A ⇌ B in an ideal dilute model, equilibrium [A]=1 mol/L and [B]=2 mol/L. Find Kc=[B]/[A].Show answer

1. Substitute equilibrium concentrations. 2. Kc=2/1=2.

Swipe sideways to move between sections

Concepts and Models

Objective: Explain the concepts and assumptions used in equilibrium foundations.

Formulas

Kc≈product concentration factors/reactant concentration factors
Q<K: net forward; Q>K: net reverse

Worked examples

Try itFor A ⇌ B in an ideal dilute model, equilibrium [A]=1 mol/L and [B]=2 mol/L. Find Kc=[B]/[A].Show answer

1. Substitute equilibrium concentrations. 2. Kc=2/1=2.

Applications and Worked Problems

Objective: Apply equilibrium foundations to calculations, evidence, and specified situations.

For the application problems, define the system and list the quantities supplied before choosing a relation. Use Kc≈product concentration factors/reactant concentration factors; Q<K: net forward; Q>K: net reverse. The relation must match the stated conditions. Convert to compatible units before substitution, preserve intermediate precision, and report the requested quantity with its unit or sign. When comparing alternatives, check the defining condition rather than a superficial word match. The worked examples below show the setup and calculation separately.

Formulas

Kc≈product concentration factors/reactant concentration factors
Q<K: net forward; Q>K: net reverse

Worked examples

Try itFor A ⇌ B in an ideal dilute model, equilibrium [A]=1 mol/L and [B]=2 mol/L. Find Kc=[B]/[A].Show answer

1. Substitute equilibrium concentrations. 2. Kc=2/1=2.

Try itFor A ⇌ 2B, [A]=1 and [B]=2 mol/L. Find the classroom concentration ratio [B]²/[A].Show answer

1. Apply the exponent from the balanced coefficient. 2. 2²/1=4.

You finished the reading!

Lock it in with a few practice questions. This is the last lesson in the chapter.

Practice

Previous lessonReaction Rates

Last lesson