Question

Buffering action of a mixture of ch3cooh and ch3coona is maximum when the ratio of salt to acid is equal to

Answer 1

The ratio of salt to acid is equal to 1 due to following reasons:-

- Buffer solution is the mixture of weak base with its conjugate acid or the weak acid with conjugate base.

- Change in pH is resisted by buffer solution on the addition of strong base or acid present in small amount.

- Buffering action is maximum when,

pH = pKa + 1 or pKa - 1

- As , In CH3COOH the acidity of (H) hydrogen is 1 and in CH3COONa the basicity of sodium (Na) is 1.

- So, Applying Henderson's equation,

pH = log [salt]/ [acid] - log Ka

- pH = log 1/1 - log Ka

i.e the buffering action is maximum

- Hence, The ratio of salt to acid is equal to 1.