1.

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

Answer»

`OH^(-)` concentration DECREASES
only group III radical get precipitated as HYDROXIDE but others with high solubility product do not
`K_(sp)` of group III hydroxide is high
Group III radicals get precipitated as chlorides

Solution :`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.


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