Chemistry
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.
Electrolysis
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Answer
(i) Pure water is almost a non-electrolyte and will not normally conduct electricity. It consists almost entirely of molecules. It can be electrolytically decomposed by addition of traces of dil. H2SO4 which dissociates as: H+1 and SO42- and help in dissociating water into H+1 and OH- ions, water being a polar solvent. Hence, pure water a non-electrolyte, becomes an electrolyte on addition of dil. H2SO4
(ii) The blue colour of CuSO4 solution is due to the Cu2+ ions. During it's electrolysis using Pt electrodes, at the cathode Cu2+ ions are discharged as neutral copper atoms by accepting electrons. These are not replaced by Cu2+ ions from the Anode because at the Anode, OH- ions are discharged. Hence, the blue colour of CuSO4 solution fades and it becomes almost colourless on it's electrolysis using Pt electrodes.
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