`Zn(OH)_(2)` is not precipitated when `NH_(4)OH` is added to a zinc salt solution containing some ammonium chloride. Explain.

Explanation

`Zn(OH)_(2)` can precipitated if the product of the ionic concentration of the ions furnished by the salt in aqueous solution exceeds the `K_(sp)` value of the hydroxide. Addition of `NH_(4)CI` to the aqueous solution of the zinc salt in which `NH_(4)OH` has been added as the precipitating reagent will suppress the `OH^(-)` ions concentration in solution due to common ion effect `(NH_(4)^(+)` ions being the common ions.) This means that the concentration of the `OH^(-)` ions in solution will be sufficiently suppressed or decreased and the product of ionic concentration will be less than the `K_(sp)` value of `Zn(OH)_(2)` and it will not be, therefore, precipitated.
`NH_(4)OH overset((aq))(hArr) NH_(4)^(+) (aq) + OH^(-) (aq)`
(Weak base)
`NH_(4)CI overset((aq))(to) NH_(4)^(+) (aq) +CI^(-) (aq)`