Complexometry Flashcards
The process based on the formation of a complex substance in the course of analysis.
Complexometry (complex-formation method)
Complexation Method uses:
Calcium (Ca)
Copper (Cu)
Mercury (Hg)
Magnesium (Mg)
Zinc (Zn)
Aluminum (Al)
Bismuth (Bi)
EDTA will react with metal ions to form a water-soluble stable complex or a ?
chelate compound
When a metal ion combines with a molecule which donate electrons, the resulting compound is termed a ?
complex
The complex is called a chelate if?
If the combining molecule contains two or more groups that donate electrons.
The groups bound to the central ion are called ?
Ligands
Types of Ligands
1,4,7-triazaheptane
Ethane-1,2-diamine
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 ?
greater than 8
These elements forms very weak complex.
Li, Na
Ks is below 8
Ag and Ba
Colored metals
Fe and Cu
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
Qualities of a good indicator are:
_________ of color change at the endpoint
sharpness
Qualities of a good indicator are:
___________ of the indicator for the metal ion under the conditions of the analysis
specificity
Qualities of a good indicator are:
____________ 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.
stability constant
Indicators
Eriochrome black
Dithiazone
Hydroxynaphthol blue
The indicator used is __________________ for Calcium containing compounds. (deep blue)
hydroxynaphthol blue
Zinc compounds and their preparations requires ?
Eriochrome black T.S. (red to blue)
Standard Solution
EDTA -
Primary Standard -
Indicator -
Ligand -
EDTA-disodium EDTA solution 0.05M
Primary Standard: calcium carbonate
Indicator: hydroxynaphthol blue (endpoint - appearance of a deep blue color)
Hexadentate ligand
Used for assay Ca, Mg and Zn
Calcium chloride
Zinc sulfate
Ca in water or water hardness
Used for assay of Al, Bi compounds
- Residual EDTA is determined using ?
Metal-ion solution (Zinc sulfate) and stable indicator (dithiazone)
Metal ions(minerals) that are dissolved in the ground water.
Hardness of Water
Hardness of Water
Temporary and Permanent (__________________________________)
Ca2+, Mg2, Fe3+ and SO₄
measure of the capacity of the water to precipitate soap
Soap scum, clog pipe
Hardness of Water, ppm
parts per million
Hardness of Water
0 to <75
Soft
Hardness of Water
75 to <150
Medium hard
Hardness of Water
150 to <300
Hard
Hardness of Water
300 and greater
Very hard
The term used to indicate the determination of a metal in the presence of another metal.
Complexometry - Masking
Complexometry - Masking may proceed by adjusting the the pH or with the use of ?
auxilliary complexing agents
Salts formed between calcium and magnesium are salts of bicarbonate.
CAN be removed by boiling.
E.g. Calcium carbonate, Magnesium carbonate
Temporary Water
Examples of Temporary Water
Calcium carbonate
Magnesium carbonate
Permanent - anions that forms salt with Ca and Mg are sulfates.
CANNOT be removed by boiling.
E.g. Calcium sulfate, Magnesium sulfate (Ca2+, Mg+2, Fe3+ and SO4-)
Permanent Water
Examples of Permanent Water
Calcium sulfate
Magnesium sulfate
(Ca2+, Mg+2, Fe3+ and SO4-)
2 types of hardness of water
Temporary
Permanent
