Direct titration of `I_(2)` with a reducing agent is called iodimetry. If `I_(2)` is leberated by the oxidation of `I_(ɵ)` ion by a strong oxidising agent in neutral or acidic medium, the liberated `I_(2)` is then titrated with reducing agent. Iodometry is used to estimate the strngth of the oxidising agent. For example, in the estimation of `Cu^(2+)` with `S_(2)O_(3)^(2-)`
`Cu^(2+)+I^(ɵ)toCuI_(2)+I_(2)` (iodometry)
`I_(2)+S_(2)O_(3)^(2-)toS_(4)O_(6)^(2-)+I^(ɵ)` (iodimetry)
Strach is used as an indicator at the end point, which forms bluecoloured complex with `I_(3)^(ɵ)` Disappearance of blue colourindicates the end point whe free `I_(2)` in not present.
Q. The volume of KI solution used for `CuSO_(4)` is:

Options

A. 1L
B. 2L
C. 4L
D. 5L

Answer

C

Explanation

`1 mol CuSO_(4)-=1 mol S_(2)O_(3)^(2-)`
`-=(1)/(2)mol I_(2)-=2 mol KI`
`-=0.4xx2=0.8mol`
`therefore0.2MxxV=0.8`
`V=4L`