Answer: Option (3) is the correct answer.
Explanation:
In an aqueous solution, a compound exists in the form of ions that is in the form of protons and electrons.
Protons are positively charged and electrons are negatively charged. A proton (usually hydrogen ion, \(H^{+}\)) in water (solvent) also exists as \(H_{3}O^{+}\).
For example, \(H_{2}O + HCl \rightleftharpoons H_{3}O^{+} + Cl^{-}\)
This shows that the conjugate acid of \(H_{2}O\) is \(H_{3}O^{+}\).
Thus, we can conclude that a hydrogen ion, H+, in aqueous solution may also be written as \(H_{3}O^{+}\).
