(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.

(a) Complete the following chemical equations : (i) MnO_(4)^(-) (aq)

1.	(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.
Answer» SOLUTION :Configurationof `La^(3+) is 4F^(0)` and that of `Lu^(3+) is 4f^(14)` . Due to the absence of partially FILLED f-orbitals, `La^(3+)` and `Lu^(3+)` do not SHOW any colour in solution.