Explain the Mechanism or working of a basic buffer.

Explanation

Consider a basic buffer solution,
`NH_(4)OHhArrNH_(4)^(+)+OH^(-),NH_(4)Cl toNH_(4)^(+)+Cl^(-)`
Here, ammonium hydroxide is a weak electrolyte, in solution there exist equilibrium between it is ions and molecules, whereas ammonium chloride completely dissociates into its ions.
Therefore, this basic buffer solution contains a large number of `NH_(4)^(+)` ions followed by `Cl^(-),OH^(-)andNH_(4)OH`.
Case (i) When a base is added to this solution:
`OH^(-)` ion of the base combines with the `NH_(4)^(+)` ion of the buffer solution and maintains equilibrium forming ammonium hydroxide.
`NH_(4)^(+)+OH^(-)hArrNH_(4)OH`, As a result pOH remains constant
Case (ii) When an acid is added to this solution :
`H^(+)` ion of the acid combines with the `OH^(-)` ion of the buffer solution and forms a water molecule.
`H^(+)+OH^(-)toH_(2)O`
As a result pOH remains constant.