`Zn^(2+)` salt are white while `Cu^(2+)` salts are blue. Assign reason.

Why Zn^(2+) salts are white while Ni^(2+) salts are blue

(a) Why are Zn^(2+) salts white while Cu^(2+) salts are blue ? (b) What is meant by 'disproportionation' ? Write the disproportionation reaction of Cu^+ in aqueous solution.

(a) What is Lanthanoid contration ? What are its important effects ? (b) Account for the following : (i) Zn^(2+) salts are white while Ni^(2+) salts are coloured. (ii) Ionisation enthalpies of 5d series elements are higher than the corresponding 3d series elements

Explain why Zn^(2+) salts are colourless while Ni^(2+) salts are coloured ?

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.