Explain Mechanism or working of an acid buffer:

Explanation

Consider the acidic buffer mixture,
`CH_(3)COOHhArrCH_(3)COO^(-)+H^(+),CH_(3)COONatoCH_(3)COO^(-)+Na^(+)`
Here, acetic acid is a weak electrolyte and its solution there exists equilibrium between its ions and molecules, whereas sodium acetate completely dissociates into its ions.
Therefore, the buffer mixture contains large number of `CH_(3)COO^(-)` ions followed by
`Na^(+),H^(+),CH_(3)COOH`.
Case (i) When an acid is added to this solution:
`H^(+)` ion of the acid combines with `CH_(3)COO^(-)` ion in the buffer solution and makes equilibrium forming acetic acid.
`CH_(3)COO^(-)+H^(+)hArrCH_(3)COOH`
As a result pH remains constant
Case (ii) When a base is added to this solution:
`OH^(-)` ion of the base combines with `H^(+)` ion in the buffer solution to form a water molecule
`H^(+)+OH^(-)toH_(2)O`
As a result pH remains constant.