Study Set Content:
Based in the formation of complex between the analyte and the titrant.
Complexation – Precipitation
The chelating agent is very commonly used to titrate metal ions in solutions.
EDTA
Before complexation what is used to determine inorganic ions and polyvalent ions such as, Al, Zn, Ca, Cu, Bi and Hg.
Gravimetric method
EDTA
disodium ethylenediamine tetraacetate
will react with metal ions to form water soluble, stable complex or chelate compounds.
EDTA
It is when a metal ion combines with a molecule which can donate electrons.
Complex
It is when the combining molecule contains two or more groups of that donates electron.
Chelate
A chelating agent. It has six bonds or points of attachment between the metal
EDTA
HOW MANY OXYGEN IN EDTA
4
HOW MANY NITROGEN IN EDTA
2
The four oxygen and two nitrogen of EDTA is capable of entering a complexation process forming a
hexadentate molecule.
The molecule of EDTA, which provides a group of attachment to metal ions, is called a
Ligand
A complex ion forms from a metal ion and a ligand because of a
Lewis acid-base interaction.
The positively charged metal ions acts as a
Lewis Acid
and the ligand, with one or more lone pairs of electrons, acts as a
Lewis base
A term used to indicate the determination of a metal in the presence of another metal.
Masking
An effective masking agent is the
cyanide ion
Formation of insoluble substances to be used for assay.
Precipitimetric Method
Precipitimetric Method Formation of insoluble substances to be used for assay.
Example methods:
● Fajan
● Mohr
● Volhard
● Liebig
● Gay-lussac
Assays are based on formation of insoluble substances or precipitates to cause the reaction to go into sufficient completion to be quantitative in nature.
Determination of end point may be determined by the following:
Cessation of precipitation or appearance of turbidity. Use of internal indicator instrumental methods. Ex. Potentiometry or amperometry.
