THE HYDROGEN ION CONCENTRATION AND BUFFERS

It is important to make the distinction between the concentration of H+ and the concentration of an acid. To show this difference, compare 1 m solutions of acetic acid and hydrochloric acid. The concentration of H+ in a 1 m solution of CHjCOjH is only 0.0042 mol/L. The concentration of H+ in a 1 m solution of HCl is 1 moVL. A liter of a 1 m solution of HCl contains 240 times as many H+ ions as a liter of a 1 M solution of acetic acid. 

Consider, however, the amount of NaOH that will react with 1.00 L of 1.00 m acetic acid. The reaction is 

CH3CO2H + Na+ + OH- Na+ + CH3CO2- + H2O acetic acid sodium hydroxide sodium acetate 

Exactly 1.00 mol of NaOH reacts with the 1.00 mol of acetic acid contained in 1.00 L of a 1.00 M solution of this acid. Exactly the same amount of NaOH reacts with the HCl in 1.00 L of 1.00 m HCl  

Therefore, even diough acetic acid is a weaker acid than hydrochloric acid, equal volumes of each, with the same molar concentration, will react with the same number of moles of base. 

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