Chemistry
Give reasons for the following:
The ratio of hydrogen and oxygen formed at the cathode and anode is 2:1 by volume.
Answer
In the electrolysis of acidified water:
At anode OH- loses one electron and becomes neutral OH.
OH- ⟶ OH + e-
The combination of OH forms water with the liberation of oxygen.
2OH + 2OH ⟶ 2H2O + O2
Since, 4 OH neutral particles are involved in the equation so 4 electrons are lost in order to get 4 OH neutral particles.
4OH- ⟶ 4OH + 4e-
Thus, the formation of 1 molecule of oxygen at the anode releases 4 electrons and to ensure that there is no build-up of electrons in any part of the circuit, the reaction of the cathode must take up 4 electrons,
i.e., 4H+ + 4e- ⟶ 2H2
This shows that the number of molecules of hydrogen is twice that of oxygen.
According to Avogadro's Law, molecules can be substituted by volumes. Hence, electrolysis of water gives 2 volumes of H2 and 1 volume of O2.
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