Which statement defines an Arrhenius acid?

Which statement defines an Arrhenius acid?

• A. Decreases H+ concentration in solution
• B. Increases OH- concentration
• C. Increases H+ concentration in solution
• D. Reacts with water to form salts

Answer: (C)

Arrhenius acids are substances that, when dissolved in water, increase the concentration of hydrogen ions. In water, free H+ doesn’t exist for long; it quickly bonds with H2O to form hydronium ions (H3O+). So adding an Arrhenius acid raises [H3O+] in the solution, which is what we recognize as acidity. That’s why the correct statement is that the acid increases H+ concentration in solution. The other ideas don’t define Arrhenius acids. Decreasing H+ concentration would make the solution less acidic, which describes a base or a neutral species. Increasing OH− concentration is characteristic of Arrhenius bases. And while acids can react with water or with other substances to form salts, the defining Arrhenius feature is the production of extra H+ (as H3O+) in aqueous solution. For example, HCl in water dissociates to H3O+ and Cl−, illustrating the increase in hydronium that marks an Arrhenius acid.

Arrhenius acids are substances that, when dissolved in water, increase the concentration of hydrogen ions. In water, free H+ doesn’t exist for long; it quickly bonds with H2O to form hydronium ions (H3O+). So adding an Arrhenius acid raises [H3O+] in the solution, which is what we recognize as acidity. That’s why the correct statement is that the acid increases H+ concentration in solution.

The other ideas don’t define Arrhenius acids. Decreasing H+ concentration would make the solution less acidic, which describes a base or a neutral species. Increasing OH− concentration is characteristic of Arrhenius bases. And while acids can react with water or with other substances to form salts, the defining Arrhenius feature is the production of extra H+ (as H3O+) in aqueous solution. For example, HCl in water dissociates to H3O+ and Cl−, illustrating the increase in hydronium that marks an Arrhenius acid.