45. Complexometry: determination of copper concentration Flashcards
What is COMPLEXOMETRY?
titrations that are suitable for quick and accurate volumetric determination of metal ions
What do titrating solutions for complexometry contain?
Titrating solutions contain chelate-forming compounds which react with the measured ions forming a stable, poorly ionizable complex with a well-defined stoichiometric proportion of the metal and the chelator.
What is te most widely used complexometric titrating agent
the solution of the sodium ethylene- diamino tetraacetate dihydrate (Komplexon III, EDTA, sodium versenate, Selecton B2, its structure forming a complex with a Ca2+ see in Fig. 1)
The titrating solution may be prepared directly by ___
the accurate measurement of EDTA (37.22 g for 1 liter 0.1 N solution)
What are complexometric indicators? Their features?
Complexometric indicators are also chelators which also form water-soluble complexes with the metal- ions at pH values suitable for the titration.
The role of EDTA in complexometry
It removes the metal ion from the metal- indicator complex and at the endpoint the original colour of the indicator can be observed.
What is The most frequently used complexometric indicator?
murexid
Materials for Determination of the concentration of copper sulfate solution (complexometry)
- 0.02 N EDTA titrating solution
- unknown CuSO4 solution
- 25 % NH3 solution
- solid murexide indicator
- glassware
Protocol of complexometry
10 ml unknown CuSO4 solution has to be measured into titrating flasks.
10 ml distilled water, 0.5 ml 25% NH3
and solid murexide are added to the solution and shake the flask to help the dissolution of the indicator.
Then titrate the copper sulfate solution with 0.02 N EDTA.
The endpoint is indicated by the occurrence of the original violet color of the indicator.
