Solutions R and S have the same concentration and are at the same temperature. One solution is hydrochloric acid, a strong acid. The other is citric acid, a weak acid.
Solution R has the lower pH. Identical strips of magnesium fizz more vigorously in R than in S.
Which statement is correct?
R is hydrochloric acid because it is fully ionised and has the higher hydrogen ion concentration.
R is citric acid because partial ionisation gives a higher hydrogen ion concentration.
R is hydrochloric acid because strong means that more acid is dissolved per cubic decimetre.
R is citric acid because a lower pH means a lower hydrogen ion concentration.
112 exam-style questions on OCR GCSE Chemistry 3.3 Types of chemical reactions, covering 3.3.1 Oxidation and reduction in terms of oxygen, 3.3.2 Acids, alkalis and neutralisation, 3.3.3 The pH scale and measuring pH, 3.3.4 Oxidation and reduction in terms of electrons, 3.3.5 Dilute and concentrated, weak and strong acids, and 3.3.6 Hydrogen ion concentration and pH. Each one has a worked solution and a mark scheme showing where the marks go.