InterviewSolution
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InterviewSolution
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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?A. All three oxidants can act as self-indicatorsB. Volume of `I_(2)` used is miniumC. Volume of `K_(2)Cr_(2)O_(7)` used is maximumD. Wt. of `KMnO_(4)` used in the titration is max |
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Answer» Correct Answer - A::B::D All three are self indicators i.e, they do not need any indicator for titration. `K_(2)S_(2)O_(3) = (0.19)/(190) = 10^(-3)mol` = 1 mmol (i) mEq of `S_(2)O_(3)^(2-) (n = 8) = ` mEq of `Cr_(2)O_(7)^(2-) (n = 6), 1 xx 8 = 0.1 xx 6 xx V` `:. V_(Cr_(2)O_(7)^(2-)) = (80)/(6)mL` (ii) mEq of `S_(2)O_(3)^(2-) (n = 1)=` mEq of `I_(2) (n = 2)` `1 xx 1 = 0.1 xx 2 xx V :. V_(I_(2)) = 5 mL` (iii) mEq of `S_(2)O_(3)^(2-) (n = 8)` = mEq of `MnO_(4)^(-) (n = 3) , 1xx 8 = 0.1 xx 3 xx V` `:. V_(MnO_(4)^(-)) = (80)/(3)mL` Also, Weight of `K_(2)Cr_(2)O_(7) = 8 xx (294)/(6) xx 10^(-3) = 0.392g` Weight of `I_(2) = 1 xx (254)/(2) xx 10^(-3) = 0.127g` Weight of `KMnO_(4) = 8 xx (158)/(3) xx 10^(-3) = 1.264g` |
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