BASIC TERMS GENERAL PROCESS TYPES 1.VOLUMETRIC 2.COLUMETRY 3.GRAVIMETRY DRAWBACKS ADVANTAGES

1. TITRAMETRIC
ANALYSIS
1

2. PRESENTED TO
PROF. BISMA TARIQ
BS CHEMISTRY 42

3. Presentation
Main Points
 BASIC TERMS
 GENERAL PROCESS
 TYPES
 VOLUMETRIC
 COLUMETRY
 GRAVIMETRY
DRAWBACKS
ADVANTAGES 3

4. INTRODUCTION
“A technique for determining the
concentration of a solution by measuring the
volume of one solution needed to completely
react with another solution. Titration process
involves addition of solution of known conc.
from burette to the measured volume of
analyte.”
4

5. Principle Of Titration
It is based on the complete chemical
reaction between the analyte and the
reagent (titrant) of known concentration.
titrant dripping out of the burette
GENERAL REACTION:
Analyte + Titrant → Product
→

6. Terms Used In Titration
• Analyte
The solution of unknown
concentration but known
volume.
• Titrant
The solution of known
concentration.
Act as determiner of conc. of
second chemical solution
6

7. STANDARD SOLUTION
A solution of known concentration is called the
standard solution
7

8. TYPES OF STANDARD SOLUTION
• Primary standard:-
It has certain properties:
(a)Extremely pure.
(b)Highly stable.
(c) Can be weighed easily.
For e.g. Na2CO3, KHP
• Secondary standard:-
It has certain properties:
(a) Less pure than primary
standard.
(b) Less stable than primary
standard.
(c) Can not be weighed easily.
For e.g. NaOH, HCl
8

9. • Equivalence Point:
Point where the amount of two
reactants are just equivalent .
• End point:
Point at which the reaction is
observed to be complete, this point is
usually observe with the help of
indicator.
• Indicator:
An auxiliary substance which helps in
the usual detection of the completion
of the titration process at the end
point.
For examples: Methyl orange,
Phenolphthalein, Cresol red, Thymol
blue
• Concentration Terms:
The concentration of standard solutions
(titrants) are generally expressed in units
of either molarity (CM, or M) or
normality (CN, or N).
• Molarity (M):
It is the number of moles of a solute per
liter of solution.
9

10. TYPES OF TITRATIONS
1) VOLUMETRIC TITRATIONS
2) COULOMETRIC TITRATIONS
3) GRAVIMETRIC TITRATIONS
10

11. VOLUMETRIC TITRATION
11

12. Volumetric titration:
• The method in which the concentration of a substance in a
solution is estimated by adding exactly the same no of
equivalants of another substance present in a solution of known
concentration.
IDEAL CONDITION:
• Reaction complete and reaction raid
12

13. 13

14. Types of volumetric titrations:
1. Simple
• Acid-base titrations
• Redox titrations
• Precipitation titrations
• Complexometric titrations
2. Back titration
3. Double titration
14

15. SIMPLE TITRATIONS:
15

16. 1-ACID-BASE TITRATION
• The type of titration which is used to find the concentration of an
acid or base in a solution by neutralizing reaction
• The estimated volume of acid in a solution can be determined
by standard solution of known concentration of base (or vise-
versa)
• The indicator is choosen based on the specific pH range of the
indicator.
16

17. • At the equivalence point in a neutralization,
moles acid=moles base
EXAMPLE:
H2SO4(aq)+2NaOH(aq)→Na2SO4(aq)+2H2O(l)
17

18. 18

19. 19

20. 20

21. 2-REDOX TITRATION:
• An oxidant can be estimated by adding known concentration of
reductant or vise versa
• EXAMPLE:
Fe+2 ion can be calculated by titration against acidified KMnO4
solution. Fe+2 is oxidized to Fe+3 ions while KMnO4 is reduced
to Mn+2 in an acidic medium
• KMnO4 is a self indicator
21

22. OVER-ALL EQUATION:
• MnO4
- + 8H+ + 5Fe2+→Mn2+ + 4H2O + 5Fe3+
22

23. •IODOMETRY &
IODIMETRY
23

24. 24

25. 3-COMPLEXOMETRIC TITRATION
• This involves the formation of complexes between the
analyte and titrant.
• These complexes may be soluble or insoluble.
Complex = metal ion + ligand
• Metal ion accepts electron (LEWIS ACID) and the
species donates electrons which are called as
ligand(LEWIS BASE)
• Commonly used ligand in complexometric titration is
EDTA – ethylene diamine tetra acetic acid or Na EDTA
– disodium salt of EDTA.
25

26. INDICATORS:
Indicator used in complexometric titration is called as “metal
indicator.” They give one color in presence of metal ions and
gives different color in absence of metal ions.
Example:
1-Solochorme black T (or EBT)
2-Modrant balck T
3-Variamine blue
4-Muxeride
26

27. EDTA-TITRATIONS:
EDTA (or
ethylenediaminetra
aceticacid) is the
most common
chelating agent or
titrant for metal ions
27

28. 28

29. PRECIPITATION REACTION:
29

30. PRECIPITATION REACTION:
(Mohar’s Method)
• It involes the formation of precipitates during titration.
• The titrant reacts with analyte forming insoluble precipitates and
it continues till the very last amount of analyte.
• When titrant is in excess, it will react with indicator resulting in
color change.
EXAMPLE:
• AgNO3+ NaCl AgCl+ NaNO3
30

31. 31

32. BACK TITRATION
• Back titration is
also titration. It is
called back
titration because it is not
carried out with the
solution whose
concentration is required
to be known (analyte) as
in the case of normal or
forward titration, but
with the excess volume
of reactant which has
been left over after
completing reaction with
the analyte. 32

33. EXPLANATION…
• In back titration you find the concentration of a species
by reacting it with an excess of another reactant of
known concentration. Then you titrate the excess
reactant.
• For example, you may want to determine the
concentration of a base, but the endpoint is not sharp
enough for a precise titration.
• You could then add excess HCl and titrate the excess
with NaOH, because this titration will give you a sharp
endpoint.
33

34. Purpose of back titration
• Back titration is designed to resolve some of the problems
encountered with forward or direct titration. Possible
reasons for devising back titration technique are :
• 1: The analyte may be in solid form like chalk in the
example given above.
• 2: The analyte may contain impurities which may interfere
with direct titration. Consider the case of contaminated
chalk. We can filter out the impurities before the excess
reactant is titrated and thus avoid this situation.
34

35. CONT…
• The analyte reacts slowly with titrant in direct or forward
titration. The reaction with the intermediate reactant can
be speeded up and reaction can be completed say by
heating.
• 4: Weak acid – weak base reactions can be subjected to
back titration for analysis of solution of unknown
concentration. Recall that weak acid-weak weak titration
does not yield a well defined change in pH, which can
be detected using an indicator.
35

36. DOUBLE TITRATION
• Double titration is a method of determining the
amount of substance present in the form of a
solution along with another solution. It can be used
in the case of a mixture of bases involving NaOH,
Na2CO3 or NaHCO3, Na2CO3. These bases are
titrated against strong acids with proper indicators.
36

37. GRAVIMETRIC ANALYSIS
37

38. GRAVIMETRIC TITRATION:
• Gravimetric analysis is the quantitative
Determination of analyte Concentration through a
Process of precipitation of the analyte, isolation of
the precipitate, and weighing the isolated product.
• Uses of gravimetric analysis:
1. Chemical analysis of ores and
industrial material.
1. Calibration of instrumentation
2. Elemental analysis of organic compounds
38

39. Gravimetric analysis
1. A weighed sample is dissolved
2. An excess of a precipitating agent Is addedto this solution
3. The resulting precipitate is filtered, dried (or ignited) and
weighed
4. From the mass and known composition Of the precipitate,
the amount of the original ion can be determined
5. Stoichiometry is important ( Write down the chemical
equation)
39

40. CRITERIA FOR GRAVIMETRIC ANALYSIS
• The desired substance must completely precipitate from
solution.
1. In most determination the precipitate Is of such low
solubility That dissolution of analyte is negligible.
2. An additional factor is the “Common ion” effect, further
reducing the solubility of the precipitate.
40

41. CRITERIA FOR GRAVIMETRIC ANALYSIS
• When Ag+ is precipitated from solution through the
addition of Cl-
Ag+ + Cl- AgCl (s)
The low solubility of AgCl is further reduced by the
Excess of Cl- that is added, Pushing the equilibrium to
the right ( Le- Chatelier’s principle
41

42. CRITERIA FOR GRAVIMETRIC ANALYSIS
• The weighed form of the product should be of known
composition.
• The product should be "pure" and easily filtered.
• It is usually difficult to obtain a product that is "pure“
(i.e., one that is free from impurities)
• Careful precipitation and sufficient washing may
reduce the level of impurities.
42

43. STEPS IN A GRAVIMETRIC ANALYSIS
1. Preparation of the solution
2. Precipitation
3. Digestion
4. Filtration
5. Washing
6. Drying or ignition
7. Weighing
8. Calculation
43

44. TYPES OF GRAVIMETRIC ANALYSIS:
• There are two main types of gravimetric analyses:
• A) Precipitation
– analyte must first be converted to a solid (precipitate) by.
precipitation with an appropriate reagent. The precipitates from
solution is filtered, washed, purified (if necessary) and weighed.
• B) Volatilization
– In this method the analyte or its decomposition products are
volatilised (dried) and then collected and weighed, or alternatively,
the mass of the volatilised product is determined indirectly by the
loss of mass of the sample.
44

45. EXAMPLE FOR PRECIPITATION
• Calcium can be determined gravimetrically by precipitation of
calcium oxalate and ignition of the oxalate ion to calcium
oxide.
• The precipitate thus obtained are weighed and the mass of
calcium oxide is determined.
45

46. EXAMPLE FOR VOLATILISATION
• The analyte or its decomposition products are volatilised at a
suitable temperature.
• The volatile product is then collected and weighed, i.e. the mass
of the product is indirectly determined from the loss in mass of
the sample.
• Example:
• Water can be separated from most inorganic compounds by
ignition, the evolved water can then be absorbed on any one of
several solid desiccants.
• The weight of water evolved may be calculated from the gain in
weight of the absorbent.
• Not all insoluble precipitates are well suited for gravimetric
analysis.
46

47. PROCESS OF PRECIPITATION
• It is a most important step in gravimetric analysis
• Involves both physical and chemical process
• The physical process consists of three steps
1. Super saturation: the solution phase contains more dissolved salt
than at equilibrium. The driving force will be for the system to
approach equilibrium (saturation).
2. Nucleation : initial phase of precipitation. A min number of particle
will gather together to form a nucleus of particle or precipitate
(solid phase). Higher degree of super saturation, the greater rate
of nucleation. It involves the formation of ion pairs and finally a
group of ions formed.
• It is of two types 1. Spontaneous 2. Induced
47

48. CONT…
• 3) Crystal growth : particle enlargement process. Nucleus
will grow by deposition of particles precipitate onto the
nucleus and forming a crystal of a specific geometric
shape. Involving two steps diffusion of ion to surface of
nucleus and Deposition on surface.
48

49. PRECIPITATION PROCESS (VON WEIMARN EQ)
Von weimarn discover – the particle size of precipitates is inversely
proportional to the relative supersaturation of the sol. during the
precipitation process.
– The von Weimarn Ratio (The lower the better)
– von Weimarn ratio = (Q – S)/S
• A measure of relative supersaturation or supersaturation ratio
• If high, get excessive nucleation, lots of small crystals, large surface
area
• If low, get larger, fewer crystals, small surface area
• S = solubility of precipitate at equilibrium, ( Keep it high with high
temperatures, adjusting pH)
• Q = concentration of reagents before precipitation (Keep it low by using
dilute solutions, stir mixture well, add reactants slowly)
• Can lower S later by cooling mixture after crystals have formed
49

50. 50

51. ADVANTAGES OF GRAVIMETRIC
ANALYSIS
• Accurate and precise: Gravimetric analysis is potentially
more accurate and more precise than volumetric analysis.
• Possible sources of errors can be checked: Gravimetric
analysis avoids problems with temperature fluctuations,
calibration errors, and other problems associated with
volumetric analysis.
• It is an ABSOLUTE method.
• Relatively inexpensive
51

52. DISADVANTAGES
• But there are potential problems with gravimetric analysis
that must be avoided to get good results.
• Proper lab technique is critical.
• Careful and time consuming.
• Scrupulously clean glassware.
• Very accurate weighing.
• Coprecipitation.
52

53. Coulometry
53

54. COULOMETRY
•Coulometry determines the amount of matter
transformed during an electrolysis reaction by
measuring the amount of electricity (in
coulombs) consumed or produced. It can be
used for precision measurements of charge, and
the Ampere even used to have a coulometric
definition.
54

55. EXAMPLE
•The sample solutions containing the ferrous ions
are added to the excess amount of the Ce (III)
ion solution.
Fe+2 →Fe+3 + e−
Ce+4 + Fe+2 → Ce+3 + Fe+3
55

56. PRINCIPLE OF COULOMETRY
• The main principle involved in the coulometry is the
measurement of the quantity of the electricity which
is directly proportional to the chemical reaction at the
electrode. This is given by the Faraday's first law:
56

57. CONTINUE……
•where Q is the consumed current; Mr is the
relative molecular weight.
57

58. THEORY
• The coulometric methods are mainly based on the
measurement of the quantity of the electricity. The sample
which is to be determined undergoes the reaction at the
electrode which is measured at the electrode. The completion of
the reaction is indicated by the decrease in the current to zero.
This can be measured by the coulometer. The substance which is
to be determined is first electrolyzed by the constant current.
Then the total current is determined by the following equation:
Total Current = Product Current × Time
58

59. ADVANTAGES OF COULOMETRY
•The following are the advantages of the
coulometric titrations:
•Standard solutions are not required.
•Reagent is generated.
•No need of the dilution of the sample solution.
•The method is readily adopted than other
methods.
59

60. Applications
• Used in the determination of the picric acid.
• Used in the separation of the nickel and cobalt.
• Used in the analysis of the radioactive materials.
• Used in the determination n-values of the
organic compounds.
• Used in the determination of the environment
pollutants.
60

61. ERRORS IN COULOMETRIC TITRATIONS
• Variation in the current during electrolysis,
• Departure of the process from 100% current
efficiency,
• Error in the current measurement,
• Error in the measurement of time, and
• Titration error due to the difference between the
equivalence point and the end point.
61

62. Types of Coulometric Methods
 Controlled potential coulometry
 Controlled current coulometry
62

63. Controlled potential Coulometry
 The working electrode will be kept at constant potential that
analyte’s quantitative reduction or oxidation occurs without
simultaneously reducing or oxidizing other species in the
solution
 The current flowing through the cell is proportional to the
analyte’s concentration. As the reactants are consumed, the
current decreases. When the reaction is complete, the
current is negligible.
The quantity of electricity is usually measured with an
electronic integrator. 63

64. 64

65. Continue….
• An analysis of this kind has all the advantages of an electro gravimetric
method, but it is not necessary to weigh a product. The technique can
therefore be applied to systems that yield deposits with poor physical
properties as well as to reactions that yield no solid product at all. For
example, arsenic may be determined coulometrically by the electrolytic
oxidation of arsenous acid (H3AsO3,) to arsenic acid (H3As04) at a platinum
anode. Similarly, the analytical conversion of iron(lI) to iron(lII) can be
accomplished with suitable control of the anode potential.
Controlled-potential coulometry is carried out in
small-volume electrochemical cells,
using electrodes with large surface areas
with high stirring rates.
65

66. The instrumentation for
potentiostatic coulometry
consists of an:
 electrolysis cell,
 a potentiostat and
 an electronic integrator
for determining the charge
consumed.
Instrumentation:
66

67. CONTROLLED CURRENT COULOMETRY
• The current is kept constant until an indicator signals
completion of the analytical reaction.
• The quantity of charge required to attain the end point is
calculated from the magnitude of the current and the time of its
passage.
Q=i x t
• Controlled-current coulometry, also known as amperostatic
coulometry or coulometric titrimetry
67

68. Continue….
• When called coulometric titration, electrons serve as
the titrant.
• An example is the titration of halides by silver ions
produced at a silver anode.
• The current in a coulometric titration is carefully
maintained at a constant and accurately known level
by means of an amperostatic.
68

69. ADVANTAGES
• First, using a constant current leads to more rapid analysis since
the current does not decrease over time. Thus, a typical analysis
time for controlled current coulometry is less than 10 min, as
opposed to approximately 30-60 min for controlled-potential
coulometry.
• Second, with a constant current the total charge is simply the
product of current and time. A method for integrating the
current-time curve, therefore, is not necessary.
69

70. Instrumentation
• Controlled-current coulometry normally is
carried out using a amperostat and an
electrochemical cell consisting of a working
electrode and a counter electrode.
• The working electrode is constructed from
Pt, is also called the generator electrode
since it is where the mediator reacts to
generate the species reacting with the
analyte. Should have a large surface area
• The counter electrode is isolated from the
analytical solution by a salt bridge or
porous frit to prevent its electrolysis
products from reacting with the analyte.
70

71. Advantages
And
Disadvantages
of Titration
71

72. ADVANTAGES
72

73. ADVANTAGES
It is generally cheap, requiring
little in the way of equipment.
It does not require a high level of
skill.
It can often be done rapidly.
Results are immediately available.
73

74. ADVANTAGES
 It is a very established, reliable, and
accurate method.
 A wide variety of reagents can be used,
making it very versatile; a lot of
different substances can be analyzed.
 Capable of higher degree of precision
and accuracy.
 Analysis can be automated.
 This method is generally robust.
74

75. DISADVANTAGES
75

76. Disadvantages
76
It is a destructive method often using up
relatively large quantities of the substance
being analyzed.
It requires reactions to occur in a liquid phase,
often the chemistry of interest will make this
inappropriate.

77. Conti…
It can produce significant amounts
of chemical waste which has to be
disposed of.
It has limited accuracy.
77

78. Uses
Medical uses
• A desired mix of compound drugs.
• Proportion of different medicines in an intravenous drip
• Monitor blood glucose levels in patients with diabetes, in pregnancy tests
and other applications of urinalysis.
Food industry uses
• Define oils, fats and similar substance
• To test free fatty acid content, unsaturated fatty acids and trace amounts of
water
• Tests for the amount of salt or sugar, and the concentration of
vitamin C or E, in a product.
• Wine and cheese production to test the product's readiness for
consumption.
78

79. Uses
Science and Education
• Titration can be employed in biology labs, where it is used to determine the proper
concentration of chemicals to anesthetize test animals. Anesthetic agents are mixed
and tested until the desired compound appropriate to a given animal is achieved.
Biodiesel Production
• Titration is used in the production of biodiesel to determine the acidity of waste
vegetable oil, one of the primary ingredients in biodiesel production. By testing a
small sample with pH paper, the pH of the entire batch can be measured and the
amount of base needed to achieve the desired pH can be determine
Aquarium Water Testing
• Titration is used to test the underwater environment in fresh water and marine
aquariums. Properties such as water pH and concentration of ammonia, nitrates and
nitrites are measured and then corrected to ensure the survival of marine life being
kept in the aquarium. 79

80. Any
Question
????
80

81. This Presentation was made with the help of
My Free Slides.com
Get More Presentations
Please Give your feedback to our Hard work Here
81