Bleaching powder and bleach solution are produced on a large scale and used in several hous-hold products. The effectiveness of bleach solution id often measured by iodometry.
`25 mL` of household bleach solution was mixed with `30 mL` of `0.50 M KI` and `10 mL` of `4N` acetic acid. In the titration of the liberated iodine, `48 mL` of `0.25 N Na_(2)S_(2)O_(3)` was used to reach the end point. The molarity of the household bleach solution is :

Options

A. `0.48`M
B. `0.96`M
C. `0.24`M
D. `0.02`M

Answer

C

Explanation

Iodiometry is the estimation of reducing substantce by the use of standard `I_(2)`.
`I_(2)+S_(2)O_(3)^(2-)rarr S_(4)O_(6)^(2-)+2I^(Theta)`
`I_(2)=2I^(Theta)=2S_(2)O_(3)^(2-)`
`Ew(S_(2)O_(3)^(2-))= (Mw)/('n'"factor") ( .:' n "factor" = (2)/(2)=1)`
`Ew(I_(2))=(Mw)/('n' "factor") ( :' n "factor" =2)`
Iodometry is the estimation of oxidising substance involving the liberation of `I_(2)` and subsequent volumetric estimation of `I_(2)`.
`2Cu^(2+) + 4I^(Theta)rarr CuI_(2)+I_(2)`
`CuI_(2)rarr Cu_(2)I_(2)+I_(2)`
`(Cu^(2+)` changes to `Cu^(Theta)`, so `Ew(Cu^(2+))=(Mw)/(1))`
`2S_(2)O_(3)^(2-)+I_(2)rarr 2I^(Theta)+S_(4)O_(6)^(2-)`
`:.` mEq of `S_(2)O_(3)^(2-) = 0.25 Nxx48(mL)=12`
mEq of `S_(2)O_(3)^(2-)-=mEq of I_(2)-=mEq of CI_(2)=12`
'n' factor for `CI_(2) = 2`
`:.` m mol of `CI_(2)=(12)/(2)=6=m` mol of `CaCOI_(2)`
`underset(('n' "factor"=2))underset("Containing" CI_(2))("Bleach") +KI+CH_(3)COOH rarr underset(('n' "factor"=2)) (I_(2))-= underset(('n' "factor"=1))(S_(2)O_(3)^(2-))`
So, molarity of `CaOCI_(2)=(m "moles")/(mL)=(6)/(25)=0.24`