InterviewSolution
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InterviewSolution
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(a) Complete the following chemical equations : (i) `MnO_(4)^(-) (aq) + S_(2)O_(3)^(2-) (aq) + H_(2)O(l) to ` (ii) ` Cr_(2)O_(7)^(2-)(aq)+Fe^(2+) (aq) + H^(+) (aq) to ` (b) Explain the following observatons : (i) `La^(3+) (Z = 57) and Lu^(3+) (Z = 71)` do not show any colour in solutions. (ii) Among the divalent cations in the first series of transition elements, manganese exhibits the maximum paramagnetism. (iii) `Cu^(+)` ion is not known in aqueous solutions. |
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Answer» (a) (i) `8 MnO_(4)^(-)(aq)+ 3 S_(2)O_(3)^(2-) (aq) + H_(2)O(l) to 8 MnO_(2) (s) + 6 SO _(4)^(2-) (aq) + 2OH^(-) (aq)` (ii) `Cr_(2)O_(7)^(2-)(aq)+6 Fe^(2+) (aq) + 14 H^(+) (aq) to 2 Cr^(3+) (aq) + 6 Fe^(3+) (aq) + 7 H_(2) O (l) ` (b) (i) It is due to obsence of unpaired electrons, `(e^(-)s)` they cannot undergo f - f transion. (ii) ` Mn^(2+)` has maximum number of unpaired electrons (iii) Since` Cu^(+)` in aqueous solution undergoes disproportionation i.e. ` 2 Cu^(+) (aq ) to Cu^(2+) (aq ) + Cu(s)` ` Cu^(2+)`(aqu) has more negative hydration energy which can over come ` 2nd` I. E energy. |
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