Analytical Chemistry

1. Quantitative method of
analysis and instrumentation

2. Analytical Chemistry:
Analytical chemistry is the branch of chemistry focused on identifying, quantifying, and
characterizing substances and their properties, enabling precise analysis and measurement in
various scientific and industrial applications.
 is mainly divided into two main classes: Qualitative Analysis & Quantitative Analysis.
 Quantitative Analysis: The basic principle of quantitative analysis is to determine the
amount or a concentration of a given sample.
There are many methods of Quantitative Analysis such as:
 Volumetric Analysis
 Gravimetric Analysis
 Photoelectric flame photometer.
 Spectroscopy
 Chromatography(not in syllabus)

3. Volumetric Analysis:
Volumetric analysis, also known as titration, is a widely used technique in analytical
chemistry. It involves the determination of the concentration of a substance (the analyte) in a
solution by reacting it with a solution of known concentration (the titrant).
The principle of volumetric analysis, also
known as titration, is based on the
concept of stoichiometry in chemical
reactions. It involves the careful
measurement of the volume of a solution
of known concentration (the titrant)
required to react completely with a
precisely measured volume of a solution
containing the analyte (the substance of
interest with an unknown concentration)
to determine its concentration or content.

4. Important Terms:
Titration:
Titration is the process of determining the volume of a known-strength (concentration) solution required to react with a known
volume of an unknown-strength solution.
Titrant and Titrate:
The solution placed in a burette during titration is called the titrant, and the solution placed in a conical flask is called the titrate.
Equivalence Point:
The volume at which the reaction actually completes, by adding a stoichiometric amount of titrant, is known as the equivalence
point or theoretical endpoint.
Indicator:
A substance used for visually detecting the completion of a particular reaction to determine the endpoint of a titration is called
an indicator.
Endpoint:
The volume at which the completion of the reaction is observed using an indicator is called the endpoint. Visual observations
may include color changes, fluorescence, or turbidity formation.
Titration Error:
In practice, there is a difference between the equivalence point and the endpoint. This difference is known as the titration error.
Standard Solution:
Volumetric Analysis depends on the use of at least one standard solution. Standard solution is the solution of known strength. A
standard solution is prepared by dissolving an accurate weighted quantity of a highly pure substance.

5. Primary Standard Solution:
A highly pure substance which is used to which is used to prepare standard solution by direct weighting it, is known as
primary standard substance. Standard solution is prepared by dissolving an accurate weighted quantity of a Primary standard
substance. Those substances whose solution can not be prepared by direct weighting are not used as a Primary standard
solution. These types of substances are called as Secondary standard substances. To qualify as a primary standard, a
substance must meet several stringent requirements:
High Purity: A primary standard must be of extremely high purity. Even small impurities can introduce errors in the
analysis, so the substance should be at least 99.9% pure.
Stability: It should be chemically stable, meaning that it doesn't react with the surrounding environment, such as air or
moisture. This stability ensures that the primary standard's composition remains constant over time.
Known Composition: The chemical composition of the substance should be well-defined and known with a high degree of
accuracy. This is essential for accurately calculating the molar mass and stoichiometry of the substance in reactions.
High Molar Mass: Ideally, the substance should have a relatively high molar mass. This makes it easier to weigh out a
precise amount of the substance during preparation.
Solubility: The primary standard should be reasonably soluble in the solvent used for the titration. This property ensures
that the substance can be accurately weighed and dissolved to prepare a standard solution of known concentration.
Non-hygroscopic: It should not be hygroscopic, meaning it should not readily absorb moisture from the atmosphere.
Hygroscopic substances can change in weight due to moisture absorption, leading to errors in concentration calculations.

6. Examples:
Acid Base titration, oxidation Reduction Titration, Precipitation Titration, Complex formation titration:
Terms used to express concentration: Normality ,Molarity, Molality, Mole fraction etc.
Application of Volumetric Analysis:
1. Determining Chemical Concentrations: Volumetric analysis is commonly used to determine the concentration
of acids, bases, salts, and other chemical species in a wide range of samples, including environmental,
pharmaceutical, and industrial solutions.
2. Quality Control in Industry: It plays a crucial role in quality control processes in industries such as food and
beverage, pharmaceuticals, and petrochemicals, where accurate determination of chemical concentrations is
essential to ensure product quality and compliance with standards.
Environmental Monitoring: Volumetric analysis is employed to assess the levels of pollutants in water and air
samples, helping to monitor and manage environmental pollution and ensure compliance with regulatory limits.
Research and Education: Volumetric analysis is a fundamental technique taught in chemistry education and is
extensively used in research laboratories for a wide range of chemical investigations, from studying reaction
kinetics to exploring complex chemical equilibria.

7. Gravimetric Analysis:
The principle of gravimetric analysis is based on the estimation of the mass percent of an ion in an impure
compound of known quantity by determining the mass of the same ion in a pure compound. In order to
determine the mass, the ion of interest needs to be completely isolated.
There are three important types of gravimetric analysis based on the
method of separation employed in the process. They are:
1. Precipitation Method: An analytical method called precipitation
gravimetry uses a precipitation reaction to separate ions from a solution.
2. Volatilization Method: In volatilization gravimetry, the sample is heated
or chemically broken down to separate the components of our mixture.
Any volatile compounds are separated out by the heating or chemical
decomposition, which causes a change in mass that can be measured.
3. Electrogravimetry Method: The principle of electrogravimetry is similar
to electroplating; here, the metal ions are isolated from the solution by
depositing on the surface of the electrode.

8. General procedure for Precipitation method:
• The first step is to selectively precipitate the analyte as a solid compound from the solution by adding a
suitable reagent. This ensures that only the analyte of interest is isolated.
• Filtration: The precipitate is separated from the solution by filtration. The precipitate is collected on a filter
paper, and the filtrate (the liquid portion) is discarded.
• Washing: The collected precipitate is washed with a suitable solvent to remove impurities or any
remaining traces of the solution.
• Drying/Ignition: The wet precipitate is dried to remove any remaining moisture.
• Weighing: The dried precipitate is carefully weighed using an analytical balance to determine its mass.
• Calculation: The mass of the precipitate is used to calculate the concentration or mass percent of the
analyte in the original sample, typically through stoichiometric calculations.

9. You are given a 50g mixture of Barium chloride and inert solid. After being
dissolved in water, an excess of silver nitrate (molar mass=169.875) is added. A
white precipitate is collected and after drying, found to have a mass of 17.48g.
Determine the purity of sample in terms of Chloride.
Given that;
molar mass of Silver (Ag)=107.87 g/mol
Molar mass of Cl=35.45 g/mol
Molar mass of Ba=137.33 g/mol

10. Solution:
Equation : BaCl2(aq) +2AgNO3 →Ba(NO3)2(aq) + 2AgCl(s)
Moles of AgCl = Mass of AgCl /Molar mass of AgCl
= 17.48 g / 143.32 g/mol=0.122 moles.
Since each mole of AgCl contains one mole of chloride ions (Cl-), the moles of Cl ions are the same as the moles of
AgCl:
Moles of Cl ions = Moles of AgCl = 0.122 moles
Molar mass of BaCl2 = 208.23 g/mol
Moles of BaCl2 = Mass of mixture / Molar mass of BaCl2
= 50 g / 208.23 g/mol = 0.240 moles
Since each mole of BaCl2 contains two moles of chloride ions (Cl-), you need to multiply the moles of BaCl2 by 2 to
get the moles of Cl ions.
=2 × Moles of BaCl2 = 2 × 0.240 moles = 0.480 moles.
Purity (%) = (Moles of Cl ions in the precipitate / Moles of Cl ions in the mixture) × 100
= (0.122 / 0.480) × 100 ≈ 25.42%

11. Spectroscopy:
Every compound present in nature possesses the property of absorbing, transmitting, or
reflecting light, which is a form of electromagnetic radiation, at specific wavelengths. This
property can be quantitatively measured using spectrophotometric techniques.
Spectrophotometry is a technique that involves measuring how light interacts with materials.
When light interacts with a material, it can be reflected, transmitted, scattered, or absorbed.
Simultaneously, the material may emit absorbed light with a different frequency due to the
energy it gains from the incident light (e.g., electroluminescence) or its temperature
(incandescence).
Several types of spectroscopic and spectrophotometric methods are applied to analyze
samples. Among them, two primary methods are highly utilized: UV-visible
spectrophotometry, which concerns itself with the reflectance of specific spectra of a given
material within the UV and visible range of the electromagnetic radiation spectrum and
absorption spectrophotometry, which is based on the absorption of radiation at specific
wavelengths of light to obtain an absorption spectrum.

12. Instrumentation
200-800nm

13. Exponential
decrease
Log10(1/T)
Transmittance to Absorbance
Absorbance(A)=Log10(1/T)
The Beer-Lambert Law describes the relationship between the absorption
of light by a substance and its concentration in a solution.
A ∝ c.l (Beer Lambert Law)
A=εcl
Where A=Absorbance, dimensionless, ε(epsilon) = molar absorptivity, also
known as the molar absorption coefficient. It has units of L/(mol·cm) or
L/(mol·dm) , C=Concentration expressed in moles per liter (M),L= the path
length(cm)
Transmittance=I/I0(where I=intensity of light that passes through the
sample and I0= intensity of light before it passes through the sample)
Absorbance(A)=Log10(1/T)
Transmittance(T)= 10-εcl
Log
10
T= Log
10 10-εCL
Log
10
T= -εCL (Log
10 10=1
-Log
10
T= εcl
Log
10(1/T) =εcl (Absorbance)

14. Question
A 0.25M solution in a test tube with path-length of 1cm has an
absorbance of 0.075 at 560nm.
1. What is the molar absorptivity of the solution?
2. What will be the absorbance if the concentration of solution is
0.65M?
3.What is the concentration of the solution if absorbance is 0.450?

15. Answers:
Question 1.
A= εcl
Ε=A/cl
=0.075/0.25M ×1cm
=0.3Lmol-1cm-1
Question 2
A= εcl
0.3Lmol-1cm-1×0.65mol/L ×1cm
=0.195
Question 3
A= εcl
C=A/εl
=0.450/0.3Lmol-1cm-1×1cm
=1.5M

16. Question:
The intensity of the incident light on a sample is
0.50w/m2 and the intensity of light entering the
detector is 0.36w/m2.Calculate the transmission and
absorbance.

17. Answer:
Transmittance=I/I0
=0.36/0.50
=0.72
Absorbance(A) = Log10(1/T)
=Log10(1/0.72)
=Log10(1.388)
=0.1427

18. Question:
A solution of thickness 3cm transmits 30%
incident light. Calculate the concentration of
the solution given that the molar absorptivity
is 4000 dm3mol-1cm-1.

19. Answer
Transmittance (T) is 30%, which means =0.30.
l=3cm
A= Log10(1/T)
=Log10(3.33)
=0.523
A=ε.c.l
c=A/ε.l
=0.523/4000dm3mol-1cm-1 ×3cm
=4.35×10-5moles dm-3

20. Homework:
Instrumentation, principle and application of flame photometer: