Titration for Purity

 

Titration can be used as a method for determining the purity of a substance by measuring the concentration of a known solution of a reactant that reacts with the substance being tested. The titration method is based on the principle of chemical equivalence, where the moles of one reactant are equal to the moles of another reactant.

For example, if you want to determine the purity of a sample of hydrochloric acid, you could perform a titration with a standardized solution of sodium hydroxide. The reaction between hydrochloric acid and sodium hydroxide is:

HCl + NaOH -> NaCl + H2O

To perform the titration, you would add a known volume of the sodium hydroxide solution to a measured volume of the hydrochloric acid sample. The reaction will continue until all of the hydrochloric acid has reacted with the sodium hydroxide, which is called the equivalence point.

At the equivalence point, the moles of hydrochloric acid and sodium hydroxide are equal, so you can calculate the concentration of the hydrochloric acid sample. If the hydrochloric acid is pure, the concentration should be equal to the theoretical concentration of hydrochloric acid.

If the concentration of the hydrochloric acid sample is lower than the theoretical concentration, then it contains impurities that react with the sodium hydroxide and consume some of the sodium hydroxide. The amount of sodium hydroxide consumed can be used to calculate the percentage purity of the hydrochloric acid sample.