Question

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?

Answer 1

When sulphuric acid is added to water, it becomes a good conductor, as the addition of sulphuric acid causes the dissociation of water molecules into H⁺ and OH⁻ ions, which are responsible for the conduction of electricity by pure water. The water thus obtained is called acidified water.

Answer 2

Pure water is non-electrolyte. All of it is made up of molecules. An electrolyte is added with a small quantity of sulphuric acid, causing the solution to ionise, giving the ions $$\mathrm{SO}{\phantom{A}}_4^{2-}$$ and H⁺. Thus, water was added with a small quantity of sulphuric acid containing the positive H⁺ ions and the negative $$\mathrm{SO}{\phantom{A}}_4^{2-}$$ and OH⁻ ions as follows:

$$\mathrm{H}{\phantom{A}}_2\mathrm{O}\stackrel{-\rightharpoonup }{\leftharpoondown -}\mathrm{H}{\phantom{A}}^{+}+\mathrm{OH}{\phantom{A}}^{-}$$

$$\mathrm{H}{\phantom{A}}_2\mathrm{SO}{\phantom{A}}_4⟶2\mathrm{H}{\phantom{A}}^{+}+\mathrm{SO}{\phantom{A}}_4^{2-}$$

Thus, the addition of H₂SO₄ helps in the ionisation of water.