Strong and Weak Acids

[Gillian Ward 1F]

Why do solutions of weak acids have higher pH values than solutions of strong acids at the
same concentration?

[Kessandra Ng 1K]

Weak acids don't fully dissociate in solution, so there is a lower concentration of H+ ion in solution. However for strong acids that fully dissociate, there are more H+ ions in solution which makes the solution more acidic and hence, have a lower pH value as compared to weak acids.

[Anita Wong 1H]

At equal concentrations, a strong acid will typically have a lower pH than a weak acid, since the strong one will donate more protons to the solution.

[Luc Lorain 1L]

Remember that the pH scale is logarithmic and starts at 0, with the pH getting more acidic the closer to 0 one gets from 7 and more basic the farther from 7 one goes in the opposite direction. A weak acid will not dissociate as willingly as a strong acid (which are often very ionic in composition, such as HCl or HI), meaning that there will simply be fewer reactions resulting in [H₃O⁺ formation when compared to a strong acid.