Chemistry
Give reason for the following:
The blue colour of aqueous copper sulphate fades when it is electrolysed using platinum electrodes.
Answer
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. As Cu2+ ions decrease, the blue colour of CuSO4 solution fades and it becomes almost colourless as soon as Cu2+ ions are finished.
Related Questions
To carry out the so-called 'electrolysis of water', sulphuric acid is added to water. How does the addition of sulphuric acid produce a conducting solution?
AB2 is a hard crystalline solid having high melting and boiling points. It conducts electricity in aqueous and molten states.
(i) AB2 conducts electricity due to the presence of free …………… (ions/molecules/electrons).
(ii) During electrolysis of AB2 in aqueous state, it is observed that cathode becomes thick and anode thin. The anode material will be …………… (graphite/metal A).
Give reason for the following:
Lead bromide undergoes electrolytic dissociation in the molten state but is a non-electrolyte in the solid state.
Give reasons for the following:
Aluminium is extracted from it's oxide by electrolytic reduction and not by conventional reducing agents.