A solution has a pH of 3 and another has a pH of 11. Identify which solution is acidic and which is basic, an…

Question

A solution has a pH of 3 and another has a pH of 11. Identify which solution is acidic and which is basic, and state which one contains a higher concentration of H⁺(aq) ions. Give a reason for your answer.

Accepted Answer

## Model Answer The solution with pH 3 is **acidic** (pH < 7), and the solution with pH 11 is **basic** (pH > 7). The solution with **pH 3 contains a higher concentration of H⁺(aq) ions**. **Reason:** According to the pH scale, higher the hydronium ion (H⁺) concentration, lower is the pH value. Since pH 3 is lower than pH 11, it has a greater concentration of H⁺(aq) ions. The solution of pH 11 has a higher OH⁻ ion concentration, making it basic. *Source: Chapter 2, Section 2.3 – How Strong Are Acid or Base Solutions?* --- ## Explanation - **1 mark** for correctly identifying pH 3 as acidic and pH 11 as basic. - **1 mark** for stating pH 3 has higher H⁺ concentration. - **1 mark** for the reason: inverse relationship between pH value and H⁺ concentration (lower pH = higher H⁺). - Remember the key rule: *pH < 7 → acidic; pH = 7 → neutral; pH > 7 → basic*. Examiners expect you to quote this principle explicitly as your reason.

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