Three different solution of oxidising agents. `K_(2)Cr_(2)O_(7),I_(2), and KMnO_(4)` is titrated separately with `0.19g of K_(2)S_(2)O_(3)`. The molarity of each oxidising agent is 0.1 M and the reaction are:
(i). `Cr_(2)O_(7)^(2-)+S_(2)O_(3)^(2-)toCr^(3+)+SO_(4)^(2-)`
(ii). `I_(2)+S_(2)O_(3)^(2-)toI^(ɵ)+S_(4)O_(6)^(2-)`
(iii). `MnO_(4)^(ɵ)+S_(2)O_(3)^(2-)toMnO_(2)+SO_(4)^(2-)`
(Molecular weight of `K_(2)S_(2)O_(3)=190,K_(2)Cr_(2)O_(7)=294,KMnO_(4)=158, and I_(2)=254 mol^(-1))` Which of the following statements is/are correct?

Options

A. All three oxidising agents can act as self-indicators
B. Volume of `I_(2)` used in minimum.
C. Volume of `K_(2)Cr_(2)O_(7)` used in maximum.
D. weight of `KMnO_(4)` used in the titration is maximum.

Answer

A, B, D

Explanation

All three are self indicato rs i.e., they do not need any indicator for titration.
`K_(2)S_(2)O_(3)=(0.19)/(190)=10^(-3)mol=1mmol`
(i). `m" Eq of "S_(2)O_(3)^(2-)(n=-8)=m" Eq of "Cr_(2)O_(7)^(2-)(n=6)`
`1xx8=0.1xx6xxV`
`V_(Cr_(2)O_(7)^(2-))=(80)/(6)mL`
(ii). `m" Eq of "S_(2)O_(3)^(2-)(n=1)=m" Eq of "I_(2)(n=2)`
`1xx1=0.1xx2xxV`
`V_(I_(2))=5mL`
(iii). `m" Eq of "S_(2)O_(3)^(2-)(n=8)=m" Eq of "MnO_(4)^(ɵ)(n=3)`
`1xx8=0.1xx3xxV`
`thereforeV_(MnO_(4)^(ɵ))=(80)/(3)mL`
Also,
Weight of `K_(2)Cr_(2)O^(7)=8xx(294)/(6)xx10^(-3)=0.392g`
Weight of `I_(2)=1xx(254)/(2)xx10^(-3)=0.127g`
Weight of `KMnO_(4)=8xx(158)/(3)xx10^(-3)=1.274g`