i. In a homogeneous equilibrium, the reactants and products are in the same phase.
e.g. Dissociation of HI:
2HI(g) ⇌ H2(g) + I2(g)
ii. In a heterogeneous equilibrium, the reactants and products exist in different phases,
e.g. Formation of NH4Cl:
NH3(g) + HCl(g) ⇌ NH4Cl(s)