Learning focus
Develop precise chemical language, connect equations and practical observations, interpret periodic trends and apply salt-preparation rules to unfamiliar examples.
Strong acid definition
A strong acid is completely dissociated in aqueous solution. Nearly every acid particle that can donate a proton has formed ions. Hydrochloric acid, nitric acid and sulfuric acid are required examples.
Weak acid definition
A weak acid is partially dissociated in aqueous solution. Most weak-acid particles remain as molecules and only a fraction produce H+ ions. Carboxylic acids such as ethanoic acid are required examples.
Equilibrium in a weak acid
Weak-acid dissociation is reversible and represented with the equilibrium symbol. Ions recombine while molecules dissociate, and the equilibrium lies mainly towards undissociated molecules under typical conditions.
Observable consequences
At the same concentration, a strong acid usually has lower pH, higher electrical conductivity and a faster initial reaction with a suitable metal or carbonate because it provides a greater H+ concentration. Comparisons must keep concentration and temperature constant.
Practical or data skill
Compare equal concentrations of hydrochloric acid and ethanoic acid using pH and electrical conductivity. Use equal volumes and the same apparatus.
Examination tip
Strong does not mean concentrated. Define strength by extent of dissociation.
Review questions and suggested answers
Question 1
Define a strong acid.
Suggested answer
An acid that is completely dissociated in aqueous solution.
Question 2
Give one weak acid example.
Suggested answer
Ethanoic acid or another carboxylic acid.
Question 3
Why does a strong acid usually conduct better at the same concentration?
Suggested answer
It produces a greater concentration of mobile ions.
