The equilibrium equation for the distribution of benzoic acid between water and ether can be expressed as follows:
Benzoic acid (aq) ⇌ Benzoic acid (org)
The distribution coefficient (Kd) is defined as the ratio of the concentration of benzoic acid in the organic phase (ether) to its concentration in the aqueous phase (water) at equilibrium. Mathematically, it can be represented as:
Kd = [Benzoic acid (org)] / [Benzoic acid (aq)]
The equilibrium expression can be written using concentrations as:
Kd = ([C6H5COOH]org) / ([C6H5COOH]aq)
Where:
- [C6H5COOH]org represents the concentration of benzoic acid in the organic phase (ether)
- [C6H5COOH]aq represents the concentration of benzoic acid in the aqueous phase (water)
This equation indicates how the distribution of benzoic acid is influenced by the relative concentrations in the organic and aqueous phases. A higher distribution coefficient (Kd) signifies a greater affinity of benzoic acid for the organic phase (ether), while a lower Kd indicates a preference for the aqueous phase (water).