1.

A blue solution of copper sulphate becomes darker when treated with excess of ammonia. This is because

Answer»

ammonia molecules REPLACE WATER molecules in the solution
ammonia is stronger ligand than water
ammonia froms a stable comlex ion `[Cu(NH_(3)_(4)]^(2+)`with Cu^(2+)` ions
All of above

Solution :`underset("BLUE")([Cu(H_(2)O)_(4)]^(2+))+SO_(4)^(2-)+4NH_(3)rarr[Cu(NH_(3))_(4)]^(2+)+4H_(2)O`
`NH_(3)` being a stronger ligand than `H_(2)O`, replaces `H_(2)O` and forms stable deep-blue coloured complex with `Cu^(2+)`.


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