An equilibrium state means a state in which all significant factors and processes remain more or less constant over a period of time.

Cato Maximilian Guldberg (1836–1902) and Peter Waage (1833–1900) first proposed the equilibrium law in 1864.

Equilibrium law - the mathematical description of a chemical system at equilibrium

When a mixture of reactants and products of a reaction reaches equilibrium at a given temperature, its equilibrium constant always has the same value.

The equilibrium law is sometimes called the law of mass action.

Common Acids and Bases in the Home

Common Acids and Bases in the Home

Le Châtelier’s principle - a generalization that states that:

chemical systems at equilibrium shift to restore equilibrium when a change occurs that disturbs the equilibrium.

An adjustment by a system at equilibrium that results in a change in the concentrations of reactants and products is called an equilibrium shift.

Le Châtelier’s principle allows chemists to predict the qualitative effects of changes in concentration, pressure, and temperature on a chemical reaction system at equilibrium.

Strong Acid/Base Weak Acid/Base


Strong acid - ionise/dissociate completely producing H+ ion

Strong base - ionise/dissociate completely producing OH- ion

All are in ions state, No molecule left

Strong electrolyte with high conductivity  


Weak acid - ionise/dissociate partially producing H+ ion

Weak base - ionise/dissociate partially producing OH- ion

Most in undissociated molecule form

Poor electrolyte with low conductivity

HCl → H+ + Cl- CH3COOH ⇌ H+ + CH3COO-