Titration is a laboratory technique used to determine the concentration of a solution (the analyte) by reacting it with a standardized solution (the titrant) of known concentration. The process involves adding the titrant gradually to the analyte until the reaction between the two is complete, which is indicated by a measurable change in the system, often signaled by a color change.
Here's an example of a titration using the reaction between a strong acid (hydrochloric acid, HCl) and a strong base (sodium hydroxide, NaOH):
Setup: A known volume of the acid solution (analyte) is placed in a flask, and a few drops of an indicator (such as phenolphthalein) are added to the flask. The indicator is a substance that changes color when the reaction between the acid and base is complete. A burette is filled with the standardized sodium hydroxide solution (titrant).
Titration process: The sodium hydroxide solution is slowly added to the acid solution in the flask while swirling the flask gently. The titrant is added drop by drop near the end point of the reaction, which is the point where the acid has been completely neutralized by the base. The indicator changes color to indicate the end point.
Endpoint determination: The color change of the indicator signals that the reaction is complete. In the case of phenolphthalein, it changes from colorless to pink when the acid is neutralized. At this point, the volume of the titrant solution required to reach the end point is recorded.
Calculation of concentration: Using the volume of the titrant required and its known concentration, the concentration of the analyte can be calculated. The balanced chemical equation for the reaction between HCl and NaOH is:
HCl + NaOH → NaCl + H₂O
By knowing the stoichiometry of the reaction, the number of moles of the analyte (HCl) can be determined from the volume and concentration of the titrant (NaOH). Finally, the concentration of the analyte can be calculated by dividing the moles of the analyte by its volume.
Note: The actual calculations depend on the specific concentrations and volumes used in the experiment.
It's important to perform titrations carefully, following proper laboratory techniques and safety precautions. Accurate measurements, precise addition of the titrant, and proper recording of data are crucial for obtaining reliable results.