Titration

Titration is the slow addition of one solution of a known concentration (called a titrant) to a known volume of another solution of unknown concentration until the reaction reaches neutralization, which is often indicated by a color change. The solution called the titrant must satisfy the necessary requirements to be a primary or secondary standard. In a broad sense, titration is a technique to determine the concentration of an unknown solution.

For acid-base titrations, a pH indicator or pH meter is used in order to determine whether neutralization has been reached and titration is complete. The information obtained from the process of titration can then be inserted into the equation, M_iV_i=M_fV_f, to determine the concentration of the unknown solution. M_i and M_f are the initial and final molarities, and V_i and V_f are the initial and final volumes.

Elements of Titration

1. The standard solution is the solution of known concentration. An accurately measured amount of standard solution is added during titration to the solution of unknown concentration until the equivalence or endpoint is reached. The equivalence point is when the reactants are done reacting.

2. The solution of unknown concentration is otherwise known as the analyte. During titration the titrant is added to the analyte in order to achieve the equivalence point and determine the concentration of the analyte.

3. The equivalence point is the ideal point for the completion of titration. In order to obtain accurate results the equivalence point must be attained precisely and accurately. The solution of known concentration, or titrant, must be added to the solution of unknown concentration, or analyte, very slowly in order to obtain a good result. At the equivalence point the correct amount of standard solution must be added to fully react with the unknown concentration.

4. The end pointof a titration indicates once the equivalence point has been reached. It is indicated by some form of indicator which varies depending on what type of titration being done. For example, if a color indicator is used, the solution will change color when the titration is at its end point.

For example, when a color indicator is being used:

To clear confusion, the endpoint and equivalence point are not necessarily equal, but they do represent the same idea. An endpoint is indicated by some form of indicator at the end of a titration. An equivalence point is when the moles of a standard solution (titrant) equal the moles of a solution of unknown concentration (analyte).

The use of an indicator is a key in performing a successful titration reaction. The purpose of the indicator is to show when enough standard solution has been added to fully react with the unknown concentration. However, an indicator should only be added when necessary and is dependent upon the solution that is being titrated. Therefore, indicators must only be added to the solution of unknown concentration when no visible reaction will occur. Depending on the solution being titrated, the choice of indicator can become a key for the success of the titration.

TASKS

1. Match the following terms with their definitions: