Give reasons for the following changes —

(i) pure water a non-electrolyte — becomes an electrolyte on addition of dil. H₂SO₄

(ii) Blue colour of aq. CuSO₄ — turns almost colourless on it's electrolysis using Pt electrodes.

'Iron is electroplated with silver' —

(i) define the term in italics

(ii) state two reasons for electroplating

(ii) state why the iron is not placed at the anode and silver at the cathode during electroplating.

State the (i) electrolyte (ii) cathode used (iii) anode used (iv) electrode reaction at cathode (v) electrode reaction at anode (vi) product at cathode and anode

during

(a) electroplating an article with nickel (b) electroplating a spoon with silver (c) purification of impure copper.

Give a reason why the metals – copper, silver and lead are electrorefined but K, Na and Ca are not.