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Standardization of EDTA solution for use in complexometric titrations

Complexometric

EDTA

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Complexometric titration » EDTA - standardization

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0.01M EDTA standardization against metallic magnesium

EDTA can be standardized against many reagents, be it metallic magnesium, calcium carbonate, metallic bismuth and so on. For best results it is good to standardize EDTA solution against the same cation and using the same method as will be later used during sample analysis. Note, that EDTA solution can be prepared without a need for standardization, as EDTA itself can be obtained in form pure enough.

Reaction taking place during titration is

Mg2+ + EDTA4- → MgEDTA2-

Titration is done in pH 10 solution. At this pH about 25% if EDTA is in first protonated form (HEDTA3-), but magnesium complex stability constant is high enough so that we don't have to worry about.

Procedure to follow:

To calculate EDTA solution concentration use EBAS - stoichiometry calculator. Download EDTA standardization against metallic magnesium reaction file, open it with the free trial version of the stoichiometry calculator.

Enter Mg mass in the upper (input) frame in the mass edit field above magnesium formula (remember to multiply it by the volume fraction of the aliquot used against total volume of magnesium solution prepared). Click n=CV button below EDTA in the output frame, enter volume of the solution used, read solution concentration.

0.01M EDTA standardization against calcium carbonate

Reaction taking place during titration is

Ca2+ + EDTA4- → CaEDTA2-

Titration is done in about 0.1 sodium hydroxide solution (pH around 13). While this is not our intent when standardizing EDTA solution, at this high pH it is possible to titrate calcium in the presence of magnesium as the latter precipitates in the form of Mg(OH)2.

Procedure to follow:

To make end point detection easier it is worth to prepare a comparison solution, identical to the titrated one; this way first color change is easier to spot.

To calculate EDTA solution concentration use EBAS - stoichiometry calculator. Download EDTA standardization against calcium carbonate reaction file, open it with the free trial version of the stoichiometry calculator.

Note, that to be consistent with the use of calcium carbonate and its molar mass, reaction equation is not the one shown above, but

CaCO3 + EDTA4- -> CaEDTA2- + CO32-

These are equivalent. Enter CaCO3 mass in the upper (input) frame in the mass edit field above calcium carbonate formula (remember to multiply it by the volume fraction of the aliquot used against total volume of magnesium solution prepared). Click n=CV button below EDTA4- in the output frame, enter volume of the solution used, read solution concentration.


Page was last modified on September 06 2009, 00:14:18.

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