Many chemical reactions are known in which two substances react in precise mole ratios to form a known product in virtually 100% yield with no side-reactions or unexpected by-products. Such reactions

may be studied conveniently by titration, the carefully-measured addition of a solution of one reactant to a known amount of the second reactant until that point at which the precisely correct mole ratio of the two reactants is reached. This point, called the end-point, may be determined with the use of an indicator. In this experiment we will study three acid-base reactions which fall into the category described above. In the first part, weighed samples of oxalic acid will be titrated with a solution of NaOH of unknown concentration. The end-point will be determined with an indicator which remains colorless so long as excess acid is present, but which turns pink when the first drop of excess NaOH is added. The molarity of NaOH can then be calculated. In the second part, a measured volume of vinegar (a solution of acetic acid) will be titrated with the same NaOH solution. Since the molarity of the NaOH solution is now known, the molarity of acetic acid in the vinegar can be calculated. Given the density of vinegar, the percent composition can also be determined. In the third part, weighed samples of an unknown monoprotic acid will be titrated with the standard NaOH solution. From the data gathered, the molar mass of the unknown acid will be determined.