Reversible Reactions

Reversible reaction definition

A reaction that can go forwards and backwards

Symbol for reversible reaction

⇌

Forward reaction

Reactants → products

Backward reaction

Products → reactants

Dynamic equilibrium definition

When forward and backward reactions occur at the same rate

Condition for equilibrium

Closed system (no substances can enter or leave)

Concentrations at equilibrium

Remain constant but not necessarily equal

Rate at equilibrium

Forward rate = backward rate

Effect of temperature on equilibrium

Favors endothermic direction when temperature increases

Effect of temperature decrease

Favors exothermic direction

Effect of pressure increase (gases)

Favors side with fewer gas molecules

Effect of pressure decrease

Favors side with more gas molecules

Effect of concentration increase

Equilibrium shifts to oppose the change

Catalyst effect on equilibrium

Speeds up both directions equally; no change in position

Example reversible reaction

Hydrated copper sulfate ⇌ anhydrous copper sulfate + water

Colour change example

Blue hydrated crystals become white when heated

Industrial importance

Allows optimisation of yield by adjusting conditions

Key idea

Equilibrium shifts to oppose changes (Le Chatelier’s Principle)