Final answer:
According to Arrhenius's theory, all acids increase the concentration of H+ ions in water.
Step-by-step explanation:
According to Arrhenius's theory, all acids increase the concentration of H+ ions in water. When an acid is added to water, it dissociates to release H+ ions. This process is represented in a chemical equation by adding H2O to the reactants side. For example, hydrochloric acid (HCl) dissociates to form H+ and Cl- ions when it is dissolved in water
Therefore, the statement 'According to Arrhenius's theory, all acids increase the hydrogen ion concentration in water' is True.