Finals T1: COMPLEXATION Flashcards
is the
process based on the formation of a complex substance in
the course of analysis.
Complexometry (complex-formation method)
use to detect elements like?
Calcium, copper, mercury, magnesium, zinc,aluminum and bismuth
will react with metal ions to form a water-soluble
stable complex or a chelate compound
or the common titrant in Complexometry
EDTA
EDTA chemical name
Ethylene diamine tetra acetic Acid
When a metal ion combines with a molecule which donate
electrons, the resulting compound is termed a _______?
Complex
If the combining molecule contains two or more groups that
donate electrons, this complex is called a ______
chelate
The groups bound to the central ion are called _______?
Ligands
Reason why Complexometric method is use?
Due to the formation of insoluble compounds, the complexometry is use to increase the solubility of the insoluble compound.
it also use to detect elements that causes hardness to the water.
Types of Ligands/ Chelating agent:
Ammonia (NH3)
Ethane-1,2-diamine (Edamine)
EDTA
1,4,7-triazaheptane (TACN)
measure of the strength of the
interaction between the reagents that come together to form the complex.
Stability constant
Stability constants should be greater than 8 = to ______
Increase complex formation
Element that forms very weak complex
Li (Lithium)
Na (Sodium)
Stability constants of an element that is below 8
Ag (Silver)
Ba (Barium)
K (Potassium)
an element that forms a colored metals
Fe (Iron)
Cu(Copper)
Stability constants (as log K) of
metal-EDTA complexes:
Mg2+: Magnesium
8.7
Stability constants (as log K) of
metal-EDTA complexes:
Ca2+: Calcium
10.7
Stability constants (as log K) of
metal-EDTA complexes:
Sr2+: Strontium
8.6
Stability constants (as log K) of
metal-EDTA complexes:
Ba 2+: Barium
7.8
Stability constants (as log K) of
metal-EDTA complexes:
Mn 2+ : Manganese
13.8
Stability constants (as log K) of
metal-EDTA complexes:
Fe 2+ : Iron II (Ferrous)
14.3
Stability constants (as log K) of
metal-EDTA complexes:
Co 2+ : Cobalt
16.3
Stability constants (as log K) of
metal-EDTA complexes:
Ni 2+: Nickel
18.6
Stability constants (as log K) of
metal-EDTA complexes:
Cu 2+: Copper
18.8
Stability constants (as log K) of
metal-EDTA complexes:
Zn 2+: Zinc
16.7
Stability constants (as log K) of
metal-EDTA complexes:
Cd2+: Cadmium
16.6
Stability constants (as log K) of
metal-EDTA complexes:
Hg2+: Mercury
21.9
Stability constants (as log K) of
metal-EDTA complexes:
Pb2+: Lead
18.0
Stability constants (as log K) of
metal-EDTA complexes:
Al3+: aluminium
16.3
Stability constants (as log K) of
metal-EDTA complexes:
Fe 3+: Iron III (Ferric)
25.1
Stability constants (as log K) of
metal-EDTA complexes:
Y3+: Yttrium
18.2
Stability constants (as log K) of
metal-EDTA complexes:
Cr3+: Chromium
24.0
Stability constants (as log K) of
metal-EDTA complexes:
Na+: Sodium
1.7
Stability with respect to pH of
some metal-EDTA complexes:
Zr4+; Zirconium
Hf4+; Hafnium
Th4+; Thorium
Bi3+; Bismuth
Fe3+’; Ferric
pH 1-3
Stability with respect to pH of
some metal-EDTA complexes:
Pb2+; Lead
Cu2+; Copper
Zn2+; Zinc
Co2+; Cobalt
Ni2+; Nickel
Mn2+; Manganese
Fe2+; Ferrous
Al3+; Aluminium
Cd2+; Cadmium
Sn2+; Tin
pH 4-6
Stability with respect to pH of
some metal-EDTA complexes:
Ca2+; Calcium
Sr2+; Strontium
Ba2+; Barium
Mg2+; Magnesium
pH 8-10
Factors affecting EDTA
reaction?
❖ Stability constant
❖ pH ( NaOH or ammonia-ammonium chloride buffer TS)
Interfering ions (cyanide, citrate, tartrate, fluoride and other
complex-forming agents)
❖ Neutral salts - NaCl
Interfering ions
cyanide,
citrate,
tartrate,
fluoride
and other complex-forming agents
organic compounds which form colored complex ions
with metal ion in high dilutions.
Indicators
Qualities of a good indicator are:
❖ sharpness of color change at the endpoint
❖ specificity of the indicator for the metal ion under the
conditions of the analysis
❖ stability constant smaller than that of the metal-EDTA
complex –i.e. the indicator must give up the metal ion to
the titrant EDTA for complexing and not compete with it.
Indicators: Complexometry
Eriochrome black,
Dithiazone and
Hydroxynaphthol
blue.
The indicator used is hydroxynaphthol blue for ____
containing compounds. ( ______)
Calcium (1)
Deep blue (2)
Standard Solution of complexometry?
EDTA – disodium EDTA solution 0.05M
Primary Standard for complexometry ?
calcium carbonate
compounds and their preparations requires
Eriochrome black T.S. (_____)
Zinc (1)
red to blue (2)
Common Indicator in coplexometry? (endpoint - appearance
of a deep blue color)
Hexadentate ligand
hydroxynaphthol blue
Inc EDTA stability constant can cause?
decrease of Indicator stability constant
*this principle is the ideal proportion to have.
Used for assay Ca, Mg and Zn
❖ Calcium chloride
❖ Zinc sulfate
❖ Ca in water or water hardness
what kind of assay they use?
Direct titration
Used for assay of Al, Bi compounds
EDTA is determined using Metal-ion solution
(Zinc sulfate) and stable indicator (dithiazone)
Residual Titration
metal ions(minerals) that are dissolved in the ground water can cause?
Hardness of water
Temporary hardness is cause by ?
Ca2+, Mg+2 carbonate
Temporary hardness can be reverse by?
Filtration and boiling the water
simple process only
Permanent of water cause by the ?
sulfates and chlorides of calcium and magnesium in water.
Permanent of hardness can be reverse by?
the need of big machine and laboratory equipments
Concentration of Calcium
Carbonate (mg/L): 0 to <75
Hardness of Water rating: Soft
Concentration of Calcium
Carbonate (mg/L): 75 to <150
Hardness of Water rating: Medium hard
Concentration of Calcium
Carbonate (mg/L): 150 to <300
Hardness of Water rating: hard
Concentration of Calcium
Carbonate (mg/L): 300 and greater
Hardness of Water rating: Very hard
The term used to indicate the determination of a metal in the
presence of another metal
This may proceed by adjusting the pH or with the use of
auxilliary complexing agents like
Masking
Zn-EDTA inactivates Hg, Cu, Bi
Masking: Thioglycols
imparts alkalinity Mg-EDTA over
Al-EDTA
Fe, Al,
Masking: TEA (triethanolamine)
mask the Zn, Co, Ni, Cu
masking: Potassium cyanide
masking – Mg, Al, Ca?
masking: Ammonium fluoride
In a solution containing the following metals: Magnesium, Zinc, Mercury,
Aluminum and Copper:
Which of these metals may form complex with EDTA if the above solution
is treated with KCN (Potassium cyanide)?
II. Zn only
If the sample will be treated with triethanolamine, which of these metal/s
will be precipitated?
IV. Al
V. Mn
Which of these metals will form a stable complex with EDTA at pH of 4- 6?
V. Mn
II. Zn
IV. Al
Which of these metals will not form complex with thioglycol?
V. Mn
IV. Al
II. Zn
I. Mg
Sodium Tetraphenylboron
Titrations chemical name and concentration?
Na(C6H5)4B (freshly prepared,0.02M)
Sodium Tetraphenyl boron
Titrations : INDICATOR
BPB (Bromophenol blue)
Sodium Tetraphenyl boron
Titrations react on what compound?
Potassium dichromate by gravimetry
Sodium Tetraphenylboron
Titrations: Extraction Indicator
Chloroform
protecting agent to protect amino acids.
Organic nitrogen compounds
❖ Alkaloids, amines, quaternary amine salts, ammonium,
potassium and silver ions
Sodium Tetraphenylboron
thioglycol chemical name ?
Di mercapto propanol