An acid is a substance that increases the concentration of h3o+ ions in solution. look at the reaction below of phenol (c6h5oh) with water: mc023-1.jpg which reactant acts as an acid by contributing a h+ ion to create h3o+ in the chemical equation? c6h5oh(aq) h2o(l) c6h5o–(aq) h3o+(aq)

Answer is: phenol (C₆H₅OH).
Chemical reaction: C₆H₅OH(aq) + H₂O(l) → C₆H₅O⁻(aq) + H₃O⁺(aq).
As reactant phenol (C₆H₅OH) has neutral charge and as product of reaction has negative charge (1-), So in this chemical reaction phenol gives one proton (H⁺) to the water and water became hydronium ion (H₃O⁺).

Ithink is d. physical property