An acid is a substance that increases the concentration of H₃O⁺ ions in solution. Look at the reaction below of phenol (C₆H₅OH) with water:
Which reactant acts as an acid by contributing a H⁺ ion to create H₃O⁺ in the chemical equation?
a. C₆H₅OH(aq)
b. H₂O(l)
c. C₆H₅O⁻(aq)
d. H₃O⁺(aq)

a. C₆H₅OH(aq)

Explanation:

The reaction of phenol with water is shown below as:-

According to Arrhenius, The specie which furnish protons in solution is known as acid. In the above reaction, phenol, acts as an acid by contributing a H⁺ ion to create H₃O⁺ in the chemical equation.

a. C₆H₅OH(aq) is the answer