In the third group of qualitive analysis, the precipitating reagent is `NH_(4)CI//NH_(4)OH`. The function of `NH_(4)CI` is to

Options

A. increases the ionisation of `NH_(4)OH`.
B. Supress the ionisation of `NH_(4)OH`.
C. Convert the ions of group theird into their respective chlorides.
D. Stabilise the hydroxides of group `III` cations.

Answer

B

Explanation

Due to common ion `(NH_(4)^(o+))`, from `NH_(4)CI`, it supresses the ionisation of `NH_(4)OH`, so as to give less concentration, of `overset(Theta)OH` ions, so that only the hydroxides of `III` group can precipitate, not the hydroxdes of higher group, since `K_(sp)` of the hydroxides of `III` group is lower than the `K_(sp)` of the hydroxides of higher group.