Which of the following compounds is known as corrosive sublimate ?

Options

A. `ZnCI_(2)`
B. `CdCI_(2)`
C. `HgCI_(2)`
D. `CuCI_(2)`

Answer

C

Explanation

The commonest among mercuty (II) halide is mercury (II) chloride, which is known as corrosive sublimate. It may be prepared by heating mercuric sulphate with common salt in the presence of little manganese dioxide:
`HgSO_(4) + 2NaCI` `overset (MnO_(2)) underset (Delta) rarr` `HgCI_(2) + Na_(2)SO_(4)`
The function of `MnO_(2)` as a reducing is to prevent the formation of any mercurous chloride. Merciric chloride sublimes off and condenses of the coolar parts of the vessel. It can be prepared by dissolving mercuric oxide in hydrochloric acid or by dissolving Hg (or `Hg_(2) CI_(2)`) in aquaregia.
(i) `HgO + 2HCI rarr HgCI_(2) + H_(2)O`
(ii) `3HCI + HNO_(3) rarr NOCI + 2H_(2)O + CI_(2)`
`Hg + 2CI rarr HgCI_(2)`
`Hg_(2)CI_(2) + 2CI rarr 2HgCI_(2)`
Mercuric chloride is commercially made by heating the metal mercury is a currenrt of chlorine:
`Hg + CI_(2) rarr HgCI_(2)`
Mercuric chloride forms white crystalline mass but form aqueous solution it crystallises into colorless needles. It is a covalent compound, readily soluble in water can be increased by the addition of chlotid ions, when a soluble tetrachlormercurate (II) complex ion is formed:
`HgCI_(2) + 2CI^(-) rarr [Hg CI_(4)]^(2-)`
It has corrosive action and is very poisonous (Its antidote is the white of an egg which eliminates it from the system in the form of a coagulated mass). On heating it sublimes. Therefore, it is known as corrosive sublimate. It has been used as an antiseptic since the middle ages.