Question

`HgCl_(2)` and `I_(2)` both when dissolved in water containing `I^(-)` ions the pair of species formed is:
A. `HgI_(2)mI_(3)^(-)`
B. `HgI_(2),I^(-)`
C. `Hgl_(4)^(2-), I_(3)^(-)`
D. `Hg_(2)I_(2),I^(-)`

Answer 1

Correct Answer - C
`HgCl_(2)` and `I_(2)` both when dissolved in water containing `I^(-)` ions, the pair of species formed is `HgI_(4)^(2-)` and `I_(3)^(-)`.
In aqueous solution, `I_(2)` reacts with `I^(-)` and maintains the following equilibrium
`I_(2)+I^(-) ltimplies I_(3)^(-)`
`Hg^(2+)` gives ppt. of `HgI_(2)` on reaction with `I^(-)`.
But `HgI_(2) +2I^(-) to underset("Red ppt")(HgI_(2))darr+2Cl^(-)`
`HgI_(2) + 2I^(-) ltimplies [HgI_(4)]^(2-)`
`HgI_(2) + 2I^(-) ltimplies [HgI_(4)]^(2) + 2I^(-) ltimplies [HgI_(4)]^(2-)`