Write down the change that will be seen in each instance and explain the reason behind it.
Answers
Answer:
If pure water is used in the electrolytic cell, current does not flow even on putting on the switch.
Pure water is a bad conductor of electricity. Dilute H2SO4 is acidulated water. The electrical conductivity of water increases on mixing with strong acid or base in it due to their dissociation and electrolysis of water takes place.
H2SO4 is fully dissociated in aqueous solution.
H2SO4 → (2H+) + (SO²4-)
H2O is a weak electrolyte and is only slightly dissociated.
H2O → (H+) + (OH-)
During electrolysis, the hydrogen ions migrate towards the cathode and are discharged there.
[ H+ ions gains electrons and are converted to hydrogen gas ]
(2H+) + (2e-) → H2
Cathode reaction:
2H2O (I) + 2e- → H2 (g) + 2OH+ (aq)
Anode reaction:
2H2O (I) → O2 (g) + (4H+) (aq) + 4e-
For every hydrogen ion discharged at the anode, another hydrogen ion is formed at the cathode. The net result is that the concentration of the sulphuric acid remains constant and electrolysis of water is overall reaction.
2H2O → 2H2 + O2
In this activity the volume of the hydrogen gas formed near the cathode is double that of the oxygen gas formed near the anode.
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