7(iv)
Acidulated water is electrolysed using platinum electrodes. Answer the following questions:
(a) Why is dilute sulphuric acid added to water?
(b) Write the reaction taking place at the cathode.
(c) What is the observation at the anode?
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(a) Water in pure state consists almost entirely of molecules. It is a polar covalent compound and can form ions when traces of dilute sulphuric acid is added.
(b) 4H+ + 4e- ⟶ 4H
2H + 2H ⟶ 2H2
(c) At the anode (positive electrode) hydroxide ions are preferentially discharged, producing oxygen gas:
4OH- - 4e- ⟶ 4OH
4OH ⟶ 2H2O + O2