Which statement best describes the Arrhenius definition of acids and bases?

• A. Acids produce H+ in solution; bases produce OH-; e.g., HCl → H+ + Cl-, NaOH → Na+ + OH-.
• B. Acids donate protons; bases donate electrons.
• C. Acids produce OH-; bases produce H+.
• D. Acids accept protons; bases donate protons.

Answer: (A)

Arrhenius acids are defined as substances that increase the concentration of hydrogen ions (H+) in aqueous solution, while Arrhenius bases increase the concentration of hydroxide ions (OH−). This is exactly what the statement describes: acids dissociate to give H+ (often represented as H3O+ in water) and bases dissociate to give OH−, as shown by HCl forming H+ (and Cl−) and NaOH forming Na+ and OH−. The other descriptions align with different acid–base theories or mix up the roles: one option swaps protons and electrons or protons with general proton transfer, and another mirrors Bronsted–Lowry ideas where acids are proton donors and bases are proton acceptors. In water, remember that H+ is actually tied up as H3O+, but representing it as H+ effectively captures the Arrhenius behavior.