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. In the reaction
`2CuSO_(4)+4KItoCu_(2)I_(2)+2K_(2)SO_(4)+I_(2)`
The equivalent weight of `CuSO_(4)` is
`(Mw=159.5g mol^(-1))`

Options

A. `10%`
B. `20%`
C. `5%`
D. `30%`

Answer

A

Explanation

eqt. of `CuSO_(4) -=` eqt. of Hypo
`(w)/(159.5) = (100xx 1)/(1000), w = 15.95g`
`:. %` purity `=(15.95)/(159.5) xx 100 = 10%`