GCSE Chemistry revision

Equilibrium

Reversible reactions and dynamic equilibrium

AQA 4.6.2.3 Foundation & Higher

Your specification

AQA student objectives

Learning pathway

ALL 🎯

MOST 🎯🎯

SOME 🎯🎯🎯

Revision summary

Read on screen, then print for Cornell-style active revision.

Equilibrium can only be reached in a closed system — a sealed environment from which no reactants or products can escape.
If products were able to escape the system, the backward reaction could never match the forward reaction, so equilibrium would never be reached.

Hydrated means that water molecules are chemically bonded within the crystal structure of the compound, as in blue hydrated copper sulphate.
Anhydrous means that no water is present in the compound, as in white anhydrous copper sulphate powder.

Reversible reactions are represented by a double arrow (⇌) and can proceed in both the forward and backward directions.
One direction of a reversible reaction is always exothermic and the other is always endothermic.
At equilibrium, the rates of the forward and backward reactions are equal and the concentrations of reactants and products remain constant.
The position of equilibrium can shift left or right depending on conditions such as temperature, and can only be established in a closed system.

3. Summary / Key Terms AQA

Reversible reactions are represented by a double arrow (⇌) and can proceed in both the forward and backward directions.
One direction of a reversible reaction is always exothermic and the other is always endothermic.
At equilibrium, the rates of the forward and backward reactions are equal and the concentrations of reactants and products remain constant.
The position of equilibrium can shift left or right depending on conditions such as temperature, and can only be established in a closed system.