The pH value for acetic acid depends on its molar concentration in an aqueous solution. Acetic acid with a molar concentration of 0.9 or approximately 1.0 M has a pH value of about 2.4, which is also the pH of vinegar that contains about 5 percent acetic acid. Acetic acid with a molar concentration of 0.1 M has a pH of 2.87, and 0.0001 M of acetic acid has a pH of 4.3.
As the molar concentration of acetic acid in a solution decreases, the pH increases, which indicates that it is a weaker acetic acid than those that have higher molar concentrations. Acetic acid is a chemical compound that has the formula C2H4O2. Its molecular weight is 60.05 grams per mole. Although acetic acid is soluble in water, chloroform and ethanol, it is insoluble in acetone.