Volumetric Analysis (Titration)
Introduction – this
analytical chemistry is branch of chemistry which deals with the analytical
substances.
Definition- It is quantitative analysis in which volume of known
concentration solution (standard solution) is required to react with
solution of unknown concentration.
Known concentration ➡➡➡ Unknown concentration =
Titration
It
is easy accurate and faster method in comparison with other quantitative
methods
It is divided into two part:
1. Qualitative analysis- Qualitative analysis
are determined the types of chemical substance
which are present in the given sample
2. Quantitative analysis- quantitative analysis are determine the amount of chemical substance which are present in the given sample.
There are various method of quantitative analysis, such as volumetric analysis, gravimetric analysis, spectrophotometry, polarimetry, polarography chromatography and biological methods, etc.
IMPORTANT TERMS USED IN TITRATION
Equivalence
point: The point where
exact enough amount of titrant are react with analyte solution to neutralize.
End
point: The point
in titration when completion of a reaction is practically observed.
The
endpoint and the equivalence point are not exactly the same. The difference
between the two is called the titration error
Titration: This method used to determine the
unknown concentration with the help of known reactant. Because volume
measurements are important role in titration, it is also known as
Titration
error- the
difference between volumes of titrant needed to reach the equivalence point and
the volume of titrant added to reach the end point in titration
OR
Difference
between the end point and the equivalence point.
Titrant:
The known
concentration of solution which is take in burette.
Analyte:
An unknown solution is determined which is take in conical flask.
Indicator: It is coloured compound reagent which
added to the analyte solution to produce physical change (change colour) OR Detection
of endpoint e.g: Phenolphthalein, Methyl Orange, Methyl red, etc.
Requirements of volumetric analysis
·
The
chemical reaction must be simple
·
The
reaction must form product
·
The reaction must show marked change at
equivalent
·
The
reaction must be stoichiometric
·
The reaction should not form any side reaction
·
The
reaction should be specific
·
The
end point of reaction should be well defined and shows visible change by using
indicator
·
The
reaction should be relatively fast
Merits of volumetric
analysis
·
It
required simple apparatus like- Burette, Burette Stand, Chronicle flask.
·
It is simple process of analysis
·
It gives quick and correct result
·
It is more precise and accurate method
Standard and
primary solution
Standard solution: A reagent of known concentration used to carry out a titrimetric
analysis (titration).
Primary standard: Is a pure
compound of standard solution which is accurately known concentration
can be prepared directly, without any need for standardization.
Requirement of primary standard solution-
·
It
should be highly pure.
·
Its
composition should not change in air or during storage
·
The
impurities present in it should not be exceed 0.01%- 0.02%
·
The
substance should be rapidly soluble in given solvent during experiment.
·
Pits
solution should be stable on keeping for long time
Uses of primary standard solution-
Acid base titration- Sodium carbonate, potassium
hydrogen, phthalate, succinic acid, Benzoic acid.
Redox titration- Potassium dichromate, potassium
iodate, oxalic acid, sodium oxalate, arsenic oxide.
Precipitation titration –Silver, silver nitrate, sodium
chloride, potassium chloride
Complex formation titration- Zinc magnesium, disodium salt, EDTA
Ethyl di-amine tetra acetic acid)
Secondary standard: Is a solution that its
concentration is not accurately known so it is to be standardized by “Primary
Standard” before use in titration.
Standardization: In this process finding the actual concentration of secondary standard
solution by titrating with suitable primary standard solution.
Percentage
of composition
Weight by weight (W/W) - the percent of
composition by weight, is the number of gram of solute present in 100 gram of
solution
Volume by volume (V/V) - The Percent composition by volume
is the volume of solute percent in 100 ml of solution.
Example- 20% of ethanol solution is prepared
by addition of 20 ml of ethanol in 80 ml of water.
Weight
By volume (W/V) -
the number of gram of solute present in 100 ml of solvent.
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