A .2M aqueous solution of formic acid is prepared.
(1) If the acid is 3% ionized, what is the concentration of the hydronium ions?
If the solution is 3% ionized, 3% of the molecules of acid have dissociated to form ions in solution.
For each mole of acid that dissociates, one mole of hydronium ions is formed. Of the .2 moles per liter, 3% of them exist as ions. The concentration of the hydronium ions is therefore given by:
Some autoionization of the water occurs as well. However, water is an extremely weak acid, and any contribution to the concentration of hydronium ions is insignificant.