Which pH range describes a strong acid?

• A. 0 to 2
• B. 3 to 6
• C. 7
• D. 8 to 14

Answer: (A)

The main idea here is how pH reflects hydrogen ion concentration and how strongly an acid dissociates in water. A strong acid fully dissociates, releasing a lot of H+ ions, which pushes the pH to very low values. That’s why ranges like 0 to 2 are the ones that describe a strong acid—these numbers correspond to a high H+ concentration.

The other ranges don’t describe a strong acid: pH 7 is neutral, pH 3 to 6 are acidic but not as extreme because the acid isn’t fully dissociated, and pH 8 to 14 are basic/alkaline with low H+ concentration.