Complexometric titration is a volumetric analysis in which the endpoint of the analysis or titration is identified by the formation of a colored complex. It is classified as direct titration, back titration, replacement titration, and alkalimetric titration of metals.
A back titration is a titration method, also called an indirect titration, that uses an excess amount of a known concentration of a substance to determine the concentration of an unknown. A chemical reaction occurs between these compounds. Since the quantity of compound with known concentration is already known, a back titration can be used to quantify the amount of the compound that has reacted with the unknown compound.
Purpose of back titration:
Back titration is intended to resolve some of the problems that can arise when using direct or forward titration. The following are some of the possible reasons for developing a back titration technique:
- Impurities in the analyte may cause problems with direct titration.
- In a direct or forward titration, the analyte reacts slowly with the titrant.
- When the acid or base is an insoluble salt, such as calcium carbonate, it is used.
- When one of the reactants, such as ammonia, is volatile.
- Back titration can be used to analyze a solution with an unknown concentration using weak acid-weak base reactions.
- When the molar concentration of an excess reactant is known, however, the strength or concentration of an analyte must be determined, and a back titration is used. In acid-base titrations, back titration is also commonly used: When the acid or base is an insoluble salt (e.g., calcium carbonate).
What is the significance of back titration in chemistry?
When the endpoint of the reverse titration is easier to identify compared to the endpoint of the regular titration, such as in precipitation reactions, back titration is useful. Back titrations are also effective when the interaction between the solute and the titrant is very slow, or when the analyte is in an insoluble solid.
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