How does titration determine the concentration of an unknown solution?

Titration determines the concentration of an unknown solution by reacting it with a solution of known concentration.

In a titration process, a solution of known concentration, called the titrant, is carefully added to a solution of unknown concentration, known as the analyte. The titrant is added until the reaction between the two solutions is complete. This point is called the equivalence point or end point, and it is usually indicated by a colour change due to the presence of an indicator.

The volume of the titrant required to reach the equivalence point is carefully measured. The stoichiometry of the reaction, which is the ratio in which the reactants combine, is known from the balanced chemical equation. Using this information, the concentration of the unknown solution can be calculated.

For example, if you are titrating hydrochloric acid (HCl) with sodium hydroxide (NaOH), the balanced equation is HCl + NaOH → NaCl + H2O. This tells us that one mole of HCl reacts with one mole of NaOH. If you know the volume and concentration of the NaOH used, you can calculate the number of moles of NaOH, which is equal to the number of moles of HCl in the solution. From this, the concentration of the HCl can be determined.

In essence, titration is a practical application of the concept of moles and stoichiometry. It is a precise and accurate method for determining the concentration of an unknown solution, provided the reaction between the titrant and the analyte is well-defined and the end point can be accurately determined.