Chemical Equilibrium
Many chemical reactions are reversible. At equilibrium, the forward and reverse reactions occur at equal rates, so concentrations remain constant. Le Chatelier's principle predicts how equilibrium shifts when conditions change.
What You Need to Know
Key Concept Diagram
Reversible reactions use a double arrow; at equilibrium both forward and reverse reactions occur simultaneously
The equilibrium constant K expresses the ratio of product to reactant concentrations
Le Chatelier's principle: if a system at equilibrium is disturbed, it shifts to minimise the disturbance
Increasing temperature favours the endothermic direction; increasing pressure favours fewer moles of gas
Key Vocabulary
Reversible reaction
A reaction that can proceed in both forward and reverse directions
Equilibrium
A state where the rate of the forward reaction equals the rate of the reverse reaction
Le Chatelier's principle
A principle stating that a system at equilibrium shifts to oppose any imposed change
Equilibrium constant (K)
A ratio of product to reactant concentrations at equilibrium
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
At chemical equilibrium, which statement is correct?
Question 2
According to Le Chatelier's principle, increasing the pressure in a gaseous equilibrium will:
Question 3
If the forward reaction in an equilibrium is exothermic, increasing temperature will:
Key Concepts Summary
- ●Reversible reactions use a double arrow; at equilibrium both forward and reverse reactions occur simultaneously
- ●The equilibrium constant K expresses the ratio of product to reactant concentrations
- ●Le Chatelier's principle: if a system at equilibrium is disturbed, it shifts to minimise the disturbance
- ●Increasing temperature favours the endothermic direction; increasing pressure favours fewer moles of gas