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The diagram given below shows the electrolysis of acidified water using platinum electrode. Study the diagram and answer the following.

The diagram shows the electrolysis of acidified water using platinum electrode. Why dil. H2SO4 is used to acidify water instead of HCl or HNO3? Write the reaction involved in the ionisation of water and sulphuric acid and name the ions that move towards the cathode and anode. Chemistry Sample Paper Solved ICSE Class 10.

(a) Why dil. H2SO4 is used to acidify water instead of HCl or HNO3?

(b) Write the reaction involved in the ionisation of water and sulphuric acid and name the ions that move towards the cathode and anode.

(c) Write the overall reaction for the electrolysis of acidified water and at what ratio hydrogen and oxygen are liberated at the cathode and anode.

Electrolysis

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Answer

(a) Dil. sulphuric acid is preferred to acidify water because it is a non-volatile acid, while dil. HCl or HNO3 are volatile acids and may decompose and interfere with the electrolytic reaction.

(b) H2O ⟶ H+ + OH-

H2SO4 ⟶ 2H+ + SO42-

H+ ions migrate to cathode, SO42- and OH- both ions migrate to anode.

(c) The ratio of hydrogen and oxygen liberated at cathode and anode is 2 : 1 by volume.
Overall reaction is:

2H2O →Electrical EnergyH2SO4\xrightarrow[\text{Electrical Energy}]{\text{H}2\text{SO}4} 2H2 + O2

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