Equilbrium in Chemical Process
Chemical equilibrium involves different chemical species in equilibrium with each other. The chemical equilibrium may be classified as homogeneous and heterogeneous depending upon whether the reaction involves only one phase or more than one phase, respectively. A few examples are listed below.
Homogenous Chemical Equilibria
H2(g) + I2(g) 2HI(g)
N2(g) + 3H2(g) 2NH3(g)
H2(g) + CO2(g) H2O(g) + CO(g)
Fe3+(aq) + SCN-(aq) FeSCN2+(aq)
CH3COOH(aq) + H2O(1) CH3COO-(aq) + H3O+(aq)
Heterogeneous Chemical Equilibira
CaCO3(s) CaO(s) + CO2(g)
Essential Characteristics of Equilibrium
- Equilibrium is possible only in a closed system at a given temperature.
- Both the opposing processes occur at the same rate and there is a dynamic but stable condition.
- All measurable properties of the system remain constant.
- When equilibrium is attained for a physical process, it is characterised by constant value of one of its parameters at a given temperature.
- The magnitude of such quantities at any stage indicates the extent to which the reaction has proceeded before reaching equilibrium.