Answer: an increase in the concentration of in aqueous solutions and is capable of donating one or more
Explanation:
According to Arrhenius concept, a base is defined as a substance which donates hydroxide ions when dissolved in water and an acid is defined as a substance which donates hydrogen ions in water.
According to the Bronsted Lowry conjugate acid-base theory, an acid is defined as a substance which donates protons and a base is defined as a substance which accepts protons.
According to the Lewis concept, an acid is defined as a substance that accepts electron pairs and base is defined as a substance which donates electron pairs.
Thus According to the Arrhenius concept, an acid is a substance that causes an increase in the concentration of in aqueous solutions and is capable of donating one or more