Chemical Equilibrium Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Chemical Equilibrium.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

A dynamic state in a reversible reaction where the forward and reverse reactions proceed at equal rates, so the macroscopic concentrations of reactants and products remain constant over time, even though molecular-level reactions continue.

The reaction is still happening both ways, but the amounts stay constant.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: At equilibrium, concentrations are stable but not necessarily equal.

Common stuck point: Equilibrium is dynamic—reactions continue, they just balance out.

Sense of Study hint: When analyzing an equilibrium problem, identify all species and write the equilibrium expression. First write the balanced reversible equation. Then set up K_{eq} as products over reactants, each raised to their coefficient power. Finally, use given concentrations or partial pressures to solve for unknowns.

Worked Examples

Example 1

easy
Explain what it means for a reaction to be at chemical equilibrium.

Solution

  1. 1
    At equilibrium, the forward reaction rate equals the reverse reaction rate.
  2. 2
    Concentrations of reactants and products remain constant (but not necessarily equal).
  3. 3
    Equilibrium is dynamic — both forward and reverse reactions continue to occur, but there is no net change.

Answer

\text{Rate}_{\text{forward}} = \text{Rate}_{\text{reverse}}
Chemical equilibrium does not mean the reaction has stopped. It means the rates of the forward and reverse reactions are balanced, so concentrations remain steady.

Example 2

medium
For the reaction \text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3, at equilibrium [\text{N}_2] = 0.50\,\text{M}, [\text{H}_2] = 1.50\,\text{M}, and [\text{NH}_3] = 0.60\,\text{M}. Calculate K_{eq}.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
For \text{N}_2\text{O}_4 \rightleftharpoons 2\text{NO}_2, if additional \text{N}_2\text{O}_4 is added, which direction does the equilibrium shift? Apply Le Chatelier's principle.

Example 2

medium
At equilibrium in a reversible reaction, have the reactions stopped? Explain what is equal at equilibrium.
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Background Knowledge

These ideas may be useful before you work through the harder examples.

chemical reactionreaction rate