Explain by giving suitable reason. (a). Yellow coloured aqueous solution of sodium chromate changes to orange-red when `CO_2` under pressure is passed. (b). Green solution of potassium manganate, `K_2MnO_4`, turns purple when `CO_2` is circulated. (c). `Hg^(2+)` and `Hg_2^(2+)` salts are colourless. (d). `Cu^(2+)` salts are paramagnetic while `Cu^(o+)` salts are diamagnetic in nature.

Explain by giving suitable reason. (a). Yellow coloured aqueous soluti

1.	Explain by giving suitable reason. (a). Yellow coloured aqueous solution of sodium chromate changes to orange-red when `CO_2` under pressure is passed. (b). Green solution of potassium manganate, `K_2MnO_4`, turns purple when `CO_2` is circulated. (c). `Hg^(2+)` and `Hg_2^(2+)` salts are colourless. (d). `Cu^(2+)` salts are paramagnetic while `Cu^(o+)` salts are diamagnetic in nature.
Answer» (a). `CO_2` gives `H^(o+)` ions which are responsible for the conversion of chromate into dichromate (orange- red). `CO_2+H_2Ounderset(larr)rarrHCO_3^(ɵ)+H^(o+)` `2CrO_4^(2-)+2H^(o+)toCr_2O_7^(2-)+H_2O` (b). `CO_2` gives `H^(o+)` ions which are responsible for conversion of `MnO_4^(2-)` into `MnO_4^(ɵ)` purple `CO_2+H_2Ounderset(larr)rarrH^(o+)+HCO_3^(ɵ)` `3MnO_4^(2-)+4H^(o+)tounderset(purpl e)(2MnO_4^(ɵ)+MnO_2+2H_2O` (c). `Hg^(2+)` and `Hg_2^(2+)` salts have `5d^(10)` configuration i.e., there is no d-d transition hence colourless. (d). `Cu^(2+)` configuration is `3d^(9)` (one orbital is singly occupied) - Paramagnetic, Cu configuration is `3d^(10)` (all orbitals are doubly occupied)- Diamagnetic.