A student says:
"A solution of a strong acid always has a lower pH than a solution of a weak acid."
Which response to the student is correct?
The student is correct, because strong acids are always more concentrated than weak acids.
The student is correct, because a strong acid is fully ionised, so it always has a higher concentration of H+\mathrm{H^{+}}H+ ions.
The student is wrong, because a very dilute strong acid can have a lower concentration of H+\mathrm{H^{+}}H+ ions than a concentrated weak acid.
The student is wrong, because weak acids are fully ionised and strong acids are only partially ionised.
53 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.