Two solutions have pH values of 3 and 11 respectively. Compare their H⁺(aq) ion concentrations and explain what each pH value indicates about the chemical nature of the solutions.
Generated by claude-sonnet-4-6 · 2026-06-26 01:04 · grounding rag
Model Answer
Comparison of H⁺(aq) ion concentrations:
On the pH scale, higher H⁺ ion concentration means lower pH. Since pH 3 < pH 11, the solution with pH 3 has a much higher concentration of H⁺(aq) ions than the solution with pH 11. In fact, the difference of 8 pH units means the H⁺ concentration of the pH 3 solution is 10⁸ times greater.
Nature of solutions:
- pH 3 → less than 7 → acidic solution (higher H⁺ ion concentration)
- pH 11 → greater than 7 → basic (alkaline) solution (lower H⁺ ion concentration, higher OH⁻ ion concentration)
A neutral solution has pH = 7.
Source: Chapter 2, Section 2.3 — How Strong Are Acid or Base Solutions?
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Explanation
- The key relationship to state: higher H⁺ concentration = lower pH value (directly from the passage: "Higher the hydronium ion concentration, lower is the pH value").
- Examiners expect you to explicitly compare the two concentrations AND identify each solution's nature (acidic/basic).
- For 3 marks: 1 mark for comparison, 1 mark for identifying pH 3 as acidic, 1 mark for identifying pH 11 as basic. Don't skip any part.
- Mentioning the neutral pH (7) as a reference point shows understanding of the scale and is good practice.