Chrominfo: What is replacement titration in chemistry?

Replacement titration is a type of complexometric titration which is used when direct or back titrations fail to produce sharp endpoints. Metal-EDTA complex is introduced to this analyte (containing metal). The presence of a metal in the analyte displaces another metal from the metal-EDTA complex.

Titrimetry, or titration, is a volumetric analysis used to determine the amount of analyte in a sample solution. It consists of a titrant that is filled into a burette, an analyte into the conical flask where the reaction takes place, and an indicator is added to produce a color change.

A known concentration of titrant is added until the reaction is completed. The titration's endpoint or equivalence point is the point at which the reaction is complete. Acid-base titrations, redox titrations, complexometric titrations, and precipitation titrations are four types of titrations that use various chemical processes and principles.

What is complexometric titration?

Complexometric titration also known as chelatometry is volumetric analysis in which the endpoint is indicated by a colored complex. In this type of titration, an indicator is used that can provide a different color change in the titration, indicating the endpoint of the titration.

Metal ion concentrations in the solution are determined using complexometric titrations. Complexometric titrations are classified as back, direct, replacement, and indirect titration methods, etc.

What is replacement titration?

The replacement method can be used to determine metal when direct or back titrations do not provide sharp endpoints or when there is no suitable indicator for analysis. The metal to be analyzed is added to the metal-EDTA complex. The analyte ion displaces EDTA from the metal, which is then titrated with standard EDTA.

This technique of titration involves displacing magnesium or zinc ions from an EDTA complex with an equivalent quantity of metal ions and then titrating the Mg or Zn ions with a standard solution of EDTA. Mordant black (Eriochrome Black T) is used as an indicator. This titration can also detect cadmium, lead, and mercury.

Example of replacement titration:

The metal to be analyzed is added to the metal-EDTA complex. The analyte ion displaces EDTA from the metal, which is then titrated with standard EDTA.

For example, when determining Mn, an excess of Mg EDTA chelate is added to the solution of Mn. Because Mn forms a more stable complex with EDTA, the Mn ions quantitatively displace Mg from the Mg-EDTA solution. The liberated Mg metal is then titrated directly with a standard EDTA solution using the Eriochrome Black T indicator.

Frequently Asked Questions (FAQ):

What are the indicators used in complexometric titration?

Eriochrome Black T, Fast Sulphon Black, Eriochrome Red B, and Murexide are common indications that are used in the complexometric titration.

What are the types of conductometry titration?

Acid-base titration, precipitation titration, replacement titration, redox (oxidation-reduction) titration, and complexometric titration are the types of conductometric titrations.

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