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

(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

(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.

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

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

Why are Cd^(2+) salts white ?

(a) Account for the following : (i) Mn shows the highest oxidation state of +7 with oxygen but with fluorine it shows the highest oxidation state of +4. (ii) Cr^(2+) is a strong reducing agent. (iii) Cu^(2+) salts are coloured while Zn^(2+) salts are white. (b) Complete the following equations : (i) 2MnO_(2) + 4KOH + O_(2) overset(Delta)(to) (ii) Cr_(2)O_(7)^(2-) + 14H^(+)6I^(-) to