Compare the hydrogen ion concentrations of two solutions: one with pH 2.0 and the other with pH 4.0. How many times greater is the [H+] in the first solution than in the second?

The calculated answer is 2.

This uses Relative Formula Mass because the objective is about (HT only) Use powers of ten to compare hydrogen ion concentrations from pH values. (MS 1b, MS 2h). This reaction focus variant asks students to separate HT only from similar Unit 4.4 chemical-change ideas. The reasoning belongs to Strong and weak acids (HT only) within Reactions of acids, so it should not be confused with nearby ideas about acids, alkalis, bases, oxidation, reduction, displacement, reactivity, electrolysis, electrodes, ions, pH, or salt preparation unless those are named in the objective. Use the focus term HT only to keep the answer aligned with AQA GCSE Chemistry 8462 Unit 4.4 Chemical changes. Keep acid, alkali and base distinct; keep oxidation and reduction distinct; do not mix reduction with displacement; keep electrolysis separate from electroplating; distinguish anode from cathode, positive ions from negative ions, oxidation state from ionic charge, and strong acid from concentrated acid.