14-08-2012, 12:46 PM
TITRATIONS
[attachment=31442]
Introduction
Titration comes from Titulus (latin) meaning inscription
Titration is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of a known reactant.
Terminology:
Since volume measurements play a key role in titrations, it is known as volumetric titrations.
Titrant- reagent of known concentration.
Titrand or analyte- reagent of unknown concentration.
Equivalence point- the point where the number of moles of titrant is equal to the number of moles of the analyte.
Indicator-reagent that changes colour around equivalence point
Method of Preparation:
Both the titrant and analyte are to be in aqueous form. If they are not they need to be diluted.
If the solution is very concentrated, it would be useful to dilute the sample.
Some titrations may require to maintain the pH. For such titrations, a buffer solution is used.
Some redox reactions may require heating the solution with the sample and titration while the solution is still hot, in order to increase the reaction rate
Procedure:
A typical titration begins with addition of the analyte into the Erlenmeyer flask with help of a pipette.
Then, some reagants are added (if necessary). E.g.- addition of MnSO4 in water while finding out the dissolved O2 content in the sample.
Next, internal indicator(if necessary) of suitable pH is added into the mixture.
Lastly, the analyte is titrated against the standard solution in the burette.
REDOX TITRATIONS:
Redox titration (also called oxidation-reduction titration) is a type of titration based on a redox reaction between the analyte and titrant.
Most commonly, a potentiometer or a redox indicator is used to determine the end-point of the titration. (e.g.-starch)
On the other hand, some redox titrations do not require an indicator, due to the intense colour of some of the constituents (e.g.-potassium permanganate)
[attachment=31442]
Introduction
Titration comes from Titulus (latin) meaning inscription
Titration is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of a known reactant.
Terminology:
Since volume measurements play a key role in titrations, it is known as volumetric titrations.
Titrant- reagent of known concentration.
Titrand or analyte- reagent of unknown concentration.
Equivalence point- the point where the number of moles of titrant is equal to the number of moles of the analyte.
Indicator-reagent that changes colour around equivalence point
Method of Preparation:
Both the titrant and analyte are to be in aqueous form. If they are not they need to be diluted.
If the solution is very concentrated, it would be useful to dilute the sample.
Some titrations may require to maintain the pH. For such titrations, a buffer solution is used.
Some redox reactions may require heating the solution with the sample and titration while the solution is still hot, in order to increase the reaction rate
Procedure:
A typical titration begins with addition of the analyte into the Erlenmeyer flask with help of a pipette.
Then, some reagants are added (if necessary). E.g.- addition of MnSO4 in water while finding out the dissolved O2 content in the sample.
Next, internal indicator(if necessary) of suitable pH is added into the mixture.
Lastly, the analyte is titrated against the standard solution in the burette.
REDOX TITRATIONS:
Redox titration (also called oxidation-reduction titration) is a type of titration based on a redox reaction between the analyte and titrant.
Most commonly, a potentiometer or a redox indicator is used to determine the end-point of the titration. (e.g.-starch)
On the other hand, some redox titrations do not require an indicator, due to the intense colour of some of the constituents (e.g.-potassium permanganate)