Under Arrhenius theory, which statement best defines an Arrhenius acid?

Under Arrhenius theory, which statement best defines an Arrhenius acid?

• A. a substance that donates H+ ions in aqueous solution
• B. a substance that accepts H+ ions
• C. a substance that donates OH- ions
• D. a substance that accepts OH- ions

Answer: (A)

The key idea is that Arrhenius acids increase the hydrogen ion concentration in water by releasing protons. When an acid dissociates in aqueous solution, it donates H+ (which in water is effectively a hydronium ion, H3O+). That’s exactly what the statement describes: a substance donates H+ ions in aqueous solution. The other options describe donating OH− (which would be an Arrhenius base) or accepting H+ or OH− (characteristics of other acid–base concepts), so they don’t match the Arrhenius definition.

The key idea is that Arrhenius acids increase the hydrogen ion concentration in water by releasing protons. When an acid dissociates in aqueous solution, it donates H+ (which in water is effectively a hydronium ion, H3O+). That’s exactly what the statement describes: a substance donates H+ ions in aqueous solution. The other options describe donating OH− (which would be an Arrhenius base) or accepting H+ or OH− (characteristics of other acid–base concepts), so they don’t match the Arrhenius definition.