On gradual addition of `KI` solution to `Bi(NO_3)_3` solution initially produces a dark brown precipitate which dissolves in excess of `KI` to give a clear yellow solution. Given an explanation for above observations.

Explanation

The gradual addition of K! solution of` Bi(NO_(3))_(2)` solution initialy produces dark brown precipitate which dissolve in excess of Ki to give a yellow solution Iodide is oxidesed to iodine which dissolve in KI to give a yellow solution of `KI_(3)`
`Bi^(3+) +H_(2)O hArr Bi(OH)^(2+) +H^(o+)`
`[NO_(3)^(Theta) + 4H^(o+) + 3e^(Theta) NO + 2H_(2)O] xx2`
`[21^(Theta) rarr I_(2) + 2e^(Theta)] xx 3 `
`ulbar (2NO_(3)^(Theta) + 8H^(o+) + 61^(Theta) rarr 2NO + 4H_(2)O + 31_(2))`
`KI +I_(2) rarr KI_(3)`