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GCSE Combined Science · key term
An acid that is only partially ionised in aqueous solution.
Used by AQA and Edexcel
Specification 5.4.2.5 · Paper 3
Revise: Strong and Weak AcidsA weak acid is only partially ionised in aqueous solution. Some acid molecules form ions, while others remain un-ionised. Ethanoic acid, citric acid and carbonic acid are the weak acids to remember.
Specification Acids · Paper 3, Paper 4
An acid that only partially dissociates into ions in aqueous solution.
Use ‘completely ionised’ for a strong acid and ‘partially ionised’ for a weak acid.
When comparing the pH of strong and weak acids, state that their acid concentrations are equal.
Compare strong and weak acids at the same concentration when explaining their different pH values.
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At the same concentration, a strong acid produces a higher concentration of hydrogen ions than a weak acid and therefore has a lower pH. A weak acid is still acidic: it produces hydrogen ions, but only some of its molecules dissociate.