Why does an aqueous solution of acid conduct electricity?

What happens when an acid reacts with a metal carbonate? Explain with the help of an example.

Write the chemical equation of the reaction involved.

What happens when carbon dioxide gas is passed through lime water for a short time and for a considerable time?

Write the equations of the reactions involved.

If we take $20 \mathrm{m}\mathrm{L}$ of the same solution of $\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}$, the amount of $\mathrm{H}\mathrm{C}\mathrm{l}$ solution (the same solution as before) required to neutralize it will be?