In third group of qualitive analysis, `NH_(4)Cl` is added before `NH_(4)OH` so that

Options

A. `OH^(-)` concentration decreases
B. only group III radical get precipitated as hydroxide but others with high solubility product do not
C. `K_(sp)` of group III hydroxide is high
D. Group III radicals get precipitated as chlorides

Answer

A, B

Explanation

`NH_(4)OH` is a weak electrolyte and dissociates partially as `NH_(4)OHhArrNH_(4)^(+)+OH^(-).`
On adding `NH_(4)Cl,` the dissociation of `NH_(4)OH` is suppressed such that `[OH^(-)]` is very less and only less soluble hydroxides are precipitated.
Hence choices (a) and (b) are correct while (c) and (d) are incorrect.