`HgCl_(2)` and `I_(2)` both when dissolved in water containing `I^(-)` ions the pair of species formed is:

Options

A. `HgI_(2), I^(-)`
B. `HgI_(4)^(2-), I_(3)^(-)`
C. `HgI_(2),I_(2), I^(-)`
D. `HgI_(2),I_(2), I_(3)^(-)`

Answer

B

Explanation

`Hf Cl_(2) + 2 I^(-) rarr 2 Cl^(-) + HgI_(2)`
`Hg I_(2) + 2 I^(-) rarr Hg I_(4)^(2-)`
Iodide forms a scarlet ppt. of mercuric iodile when added to `HgCl_(2)` solution. The ppt. of mercuric iodide dissolves in excess of iodile forming a complex ion, `Hg I_(4)^(2-)`
`I_(2) + I^(-) rarr I_(3)^(-)`
Iodine is only slightly soluble is water. Its solubility is greatly increased if some iodile ions are present in solution. The increase in solubility is due to shift of equilibrium due to formation of a polyhalide ion, `I_(3)^(-)`