Quantitative analysis is one of the important processes in chemistry. It is used to determine mass percent i.e. to determine the mass of every element present. It can also be defined as a method used to determine the number of chemicals in a sample. The mass per cent is important to find the molecular and emphatical formula.

The percentage of elements present in an organic compound can be determined by the following methods.

Table of Contents

Carbon and Hydrogen (Liebig’s method)

If we burn an organic compound in presence of excess oxygen and copper oxide, the carbon and hydrogen in the compound are oxidized to carbon dioxide and water respectively.

C_xH_y + (x + y)/4 O₂ → x CO₂ + (y/2) H₂O

In the above process, the water and carbon dioxide formed on oxidation are absorbed by anhydrous calcium chloride and potassium hydroxide solutions present in both of the U-shaped tubes. This process gives the amounts of water and carbon dioxide from which the percentage of carbon and hydrogen are calculated.

Let us consider the mass of organic compound be mg, the mass of water and carbon dioxide produced be m₁g and m₂g respectively.

So, Percentage of carbon = (12 × m₂ × 100) / (44 × m)

and Percentage of hydrogen = (2 × m₁ × 100) / (18 × m) 

Nitrogen (Dumas Method and Kjeldahl’s method)

The percentage of nitrogen can be obtained through two methods namely

1. Dumas Method
2. Kjeldahl’s method

Dumas method: The organic compound containing nitrogen when heated with copper oxide in carbon dioxide, gives free nitrogen with carbon and water.

C_xH_yN_z + (2x + y/2) CuO → xCO₂ + y/2 H₂O +z/2 N₂ + (2x + y/2)Cu

If any oxides of nitrogen are formed, they are reduced to nitrogen by passing the gaseous mixture over a heated copper gauze and is collected at the upper part of the tube. All such gases (Oxides of nitrogen) produced is brought to a solution of KOH which absorbs them.

Similar to the previous method,

Let, mg = mass of the organic compound,

V₁ mL = Volume of nitrogen collect,

T1K = Room temperature.

So, Volume of Nitrogen at STP (standard temperature and pressure) =  (p₁V₁ × 273) / (760 × T₁)

where,

• p₁ = pressure of nitrogen,
• V₁ = Volume of nitrogen.

Here, pressure is different from the atmospheric pressure at the place where nitrogen was collected. So the value of p₁ is obtained by relation,

p₁ = Atmospheric pressure – Aqueous tension

V mL N₂ at STP = (28 ×  V/ 22400) × g

So, Percentage of Nitrogen = (28 × V × 100) / (22400 × m)

Kjeldahl’s method: The compound containing nitrogen is heated with concentrated H₂SO₄ (Sulphuric acid) which results in conversion of nitrogen compound to ammonium sulphate. The resulting acid mixture after the heating is then again heated with sodium hydroxide and ammonia gas is liberated. This liberated ammonia gas is absorbed in an excess of standard solution of Sulphuric acid. The amount of ammonia produced is determined by estimating the amount of sulphuric acid consumed in the reaction and the amount of sulphuric acid consumed is determined by the amount of sulphuric acid left unreacted (by titration with standard alkali solution).

Compound + H₂SO₄ → (NH₄)₂SO₄ → (in presence of 2NaOH) 

2NH₃ + H₂SO₄ → (NH₄)₂SO₄

Let,

• mg = mass of the organic compound
• V mL = Volume of H2SO4 of molarity M
• V1 mL = Volume of NaOH of Molarity M (for titration)

V₁ mL of NaOH of molarity M = V₁/2 mL of H₂SO₄ = V₁ mL  

Volume of H₂SO₄ of molarity M unused = (V – V₁/2) mL

(V – V1/2) mL  of H₂SO₄ of molarity M = 2(V -V₁/2) mL of NH₃ solution of molarity M.

1000 mL of 1M NH₃ solution contains 17g NH3 or 14 g of N

2(V-V₁/2) mL of NH₃ solution of molarity M = [(14 × M × 2(V – V₁/2)/1000)] g N

So, Percentage of N = [(14 × M × (V – V1/2))/1000] × (100/m)

N = 1.4 × M × 2 (V – V1/2) / m

Disadvantages of Kjeldahl’s Method

1. Not applicable to compounds containing nitrogen in nitro and azo groups,
2. Not applicable for nitrogen present in Pyridine form (Ring).

Halogens

Carius Method: A certain mass of an organic compound is heated with fuming nitric acid in presence of  silver nitrate contained in hard glass tube known as Carius tube and carbon and hydrogen present in compound are oxidized in carbon dioxide and water. The halogen present mix with the corresponding silver to form its halide (AgX) which is then filtered, dried and measured.

Let,

• mg = mass of the organic compound
• m₁g = mass of AgX  (silver halide) formed

Here, 1 mol of AgX formed contains 1 mol of X.

Mass of halogen in m₁g of AgX = (atomic mass of X × m₁g) / molecular mass of AgX

Percentage of halogen = (atomic mass of X × m₁ × 100) / molecular mass of AgX × m

Sulphur

We again use the Carius tube in which we take a certain mass of an organic compound and heat it with sodium peroxide of fuming nitric acid. Sulphur present in the compound is oxidized to sulphuric acid. Then we need to add excess of barium chloride solution in water to precipitate the product as barium sulphate. The precipitate is filtered, dried, cleaned and measured.

Let,

• mg = mass of the organic compound,
• m₁g = mass of barium sulphate formed

1 mol of BaSO₄ = 233 g of BaSO₄ = 32 g Sulphur

m₁ g BaSO₄ contains 32 × m₁ g / 233 Sulphur

Percentage of sulphur = 32 × m₁ × 100 / 233 × m

Phosphorus

A certain mass of an organic compound is heated with fuming nitric acid where phosphorous present in the compound is oxidized into phosphoric acid. By adding ammonia and ammonia molybdate, it is precipitated as ammonium phosphomolybdate (NH₄)₃PO₄.12MoO₃ or alternatively, phosphoric acid may be precipitated as MgNH₄PO₄ by adding magnesia mixture which on ignition yields Mg₂P₂O₇. 

Let,

• mg = mass of the organic compound,
• m₁g = mass of ammonium phosphate molybdate

Molar mass of (NH₄)₃PO₄.12MoO₃ = 1877g

Percentage of phosphorus = (31×m₁×100/1877×m) %

If instead of phosphorus, Mg₂P₂O₇ was taken then, 

Percentage of phosphorus = (62×m₁×100/222×m) % 

where,

• 222 u =  molar mass of Mg₂P₂O₇
• m = mass of organic compound taken
• m₁ = the mass of Mg₂P₂O₇
• 62 = mass of two phosphorus atoms present in the compound Mg₂P₂O₇.

Oxygen

Every organic compound contains some percentage of oxygen in it. The percentage of oxygen can be calculated by the difference or total percentage of elements including Oxygen (100%) and the sum of all other elements present in the compound.

Alternatively, Oxygen can be emitted by chemical reaction as follows,

A certain mass of the organic compound is decomposed by heating in a stream of nitrogen gas. The mixture of gaseous products containing oxygen is passed over red hot coke when all the oxygen results in carbon monoxide. This mixture is passed through warm iodine pentoxide (I₂O₅) when carbon monoxide is oxidised to carbon dioxide which results in the production of iodine.

Organic compound → (In presence of heat) O₂ + Other gases

2C + O₂ → 2CO₂ 

I₂O₅ + 5CO → I2 + 5CO₂ 

Here we understand that each mole of oxygen released will give 2 moles of Carbon dioxide.

Thus if 32 g oxygen is released then 88 g carbon dioxide is obtained.

Let,

• mg = mass of organic compound
• m₁g = mass of carbon dioxide released

m₁g carbon dioxide is obtained from (30×m/88×m)%

The percentage of oxygen can be derived from the amount of Iodine produced.

Sample Problems

Problem 1: On Complete combustion, 0.456 g of an organic compound gave 0.254 of carbon dioxide and 0.1658 of water. Determine the percentage composition of carbon and hydrogen in the compound.

Solution:

Percentage of carbon = (12×0.254×100)/(44×0.456) 

∴ Percentage of  carbon = 15.1914 %

and Percentage of Hydrogen = (2×0.1658×100)/(18×0.456)

∴Percentage of Hydrogen = 4.03 %

Problem 2: In the dumas method for estimation of nitrogen, 0.3 g of an organic compound gave 50 mL of nitrogen collected at 300 K temperature and 715 mm pressure. Calculate the percentage composition of nitrogen in the compound. (Tension of the aqueous medium is = 15 mm)

Solution: 

Given :

• Volume of nitrogen = 50mL
• Temperature = 300 K
• Pressure = 715 mm
• Actual pressure = 715 – 15 = 700 mm

Volume of Nitrogen at STP = (273×700×50)/(300×760) = 41.9 mL,

22,400 mL of N₂ at STP weighs 28 g 

41.9 mL of Nitrogen weighs = (28×41.9)/22400 g 

∴Percentage of Nitrogen = 17.46 %.

Problem 3: In the Carius method of estimation of halogen, 0.20 g of an organic compound gave 0.16 g of AgBr (silver bromide). Find out the percentage of bromine in the compound.

Solution:

Molar mass of AgBr = 108 + 80 =188 g mol^-1

188 g AgBr contains 80 g bromine,

0.16 g AgBr contains (80×0.16)/ 188 g bromine,

Percentage of bromine = (80×0.16×100)/( 188×0.20)

∴ Percentage of bromine = 34.04 % 

Problem 5: In sulphur estimation, 0.210 g of an organic compound gave 0.5101 g of barium sulphate. What is the percentage of sulphur in the compound?

Solution:

Molecular mass of BaSO₄ = 137+32+64 = 233 g,

233 g BaSO₄ contains 32 g sulphur,

0.5010 g BaSO₄ contains (32×0.5010)/233 g sulphur,

Percentage of sulphur = (32×0.5010×100)/(233×0.210) 

∴Percentage of sulphur = 32.76 %

Problem 5: During the estimation of nitrogen present in an organic compound by Kjeldahl’s method, the ammonia evolved from 0.8 g of the compound in Kjeldahl’s estimation of nitrogen, neutralized 20 mL of 1M H₂SO₄. Find out the percentage of nitrogen in the compound. 

Solution:

1M of 20 mL H₂SO₄ = 1M of 40 mL,

NH₃ 1000 mL of 1M ammonia contains 14 g of nitrogen,

40 mL of 1M ammonia contains (14×40)/1000,

Percentage of nitrogen = (14×40×100)/(1000×0.8),

∴Percentage of Nitrogen = 70.0%  

Conceptual Questions

Question 1: Explain what happens in Liebig’s method.

Answer:

The water and carbon dioxide formed on oxidation are absorbed by anhydrous calcium chloride and potassium hydroxide solutions present in both of the U-shaped tubes. This process gives the amounts of water and carbon dioxide from which the percentage of carbon and hydrogen are calculated.

Question 2: State and define the Quantitative analysis methods of Nitrogen.

Answer:

There are 2 methods to do the quantitative analysis of Nitrogen and they are :

1. Dumas Method : The organic compound containing nitrogen when heated with copper oxide in carbon dioxide, gives free nitrogen with carbon and water.
2. Kjeldahl’s method : The compound containing nitrogen is heated with conc. H₂SO₄ which results in conversion of nitrogen to ammonium sulphate. The mixture is then again heated with sodium hydroxide and ammonia gas is liberated. This gas is absorbed in an standard solution of Sulphuric acid.

Neeraj Anand, Param Anand

Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations. In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS". He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.

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CBSE Class 11 Chemistry Syllabus

CBSE Class 11 Chemistry Syllabus is a vast which needs a clear understanding of the concepts and topics. Knowing CBSE Class 11 Chemistry syllabus helps students to understand the course structure of Chemistry.

Unit-wise CBSE Class 11 Syllabus for Chemistry

Below is a list of detailed information on each unit for Class 11 Students.

UNIT I – Some Basic Concepts of Chemistry

General Introduction: Importance and scope of Chemistry.

Nature of matter, laws of chemical combination, Dalton’s atomic theory: concept of elements,
atoms and molecules.

Atomic and molecular masses, mole concept and molar mass, percentage composition, empirical and molecular formula, chemical reactions, stoichiometry and calculations based on stoichiometry.

UNIT II – Structure of Atom

Discovery of Electron, Proton and Neutron, atomic number, isotopes and isobars. Thomson’s model and its limitations. Rutherford’s model and its limitations, Bohr’s model and its limitations, concept of shells and subshells, dual nature of matter and light, de Broglie’s relationship, Heisenberg uncertainty principle, concept of orbitals, quantum numbers, shapes of s, p and d orbitals, rules for filling electrons in orbitals – Aufbau principle, Pauli’s exclusion principle and Hund’s rule, electronic configuration of atoms, stability of half-filled and completely filled orbitals.

UNIT III – Classification of Elements and Periodicity in Properties

Significance of classification, brief history of the development of periodic table, modern periodic law and the present form of periodic table, periodic trends in properties of elements -atomic radii, ionic radii, inert gas radii, Ionization enthalpy, electron gain enthalpy, electronegativity, valency. Nomenclature of elements with atomic number greater than 100.

UNIT IV – Chemical Bonding and Molecular Structure

Valence electrons, ionic bond, covalent bond, bond parameters, Lewis structure, polar character of covalent bond, covalent character of ionic bond, valence bond theory, resonance, geometry of covalent molecules, VSEPR theory, concept of hybridization, involving s, p and d orbitals and shapes of some simple molecules, molecular orbital theory of homonuclear diatomic molecules(qualitative idea only), Hydrogen bond.

UNIT V – Chemical Thermodynamics

Concepts of System and types of systems, surroundings, work, heat, energy, extensive and intensive properties, state functions. First law of thermodynamics – internal energy and enthalpy, measurement of U and H, Hess’s law of constant heat summation, enthalpy of bond dissociation, combustion, formation, atomization, sublimation, phase transition, ionization, solution and dilution. Second law of Thermodynamics (brief introduction)
Introduction of entropy as a state function, Gibb’s energy change for spontaneous and nonspontaneous processes.
Third law of thermodynamics (brief introduction).

UNIT VI – Equilibrium

Equilibrium in physical and chemical processes, dynamic nature of equilibrium, law of mass action, equilibrium constant, factors affecting equilibrium – Le Chatelier’s principle, ionic equilibrium- ionization of acids and bases, strong and weak electrolytes, degree of ionization,
ionization of poly basic acids, acid strength, concept of pH, hydrolysis of salts (elementary idea), buffer solution, Henderson Equation, solubility product, common ion effect (with illustrative examples).

UNIT VII – Redox Reactions

Concept of oxidation and reduction, redox reactions, oxidation number, balancing redox reactions, in terms of loss and gain of electrons and change in oxidation number, applications of redox reactions.

UNIT VIII – Organic Chemistry: Some basic Principles and Techniques

General introduction, classification and IUPAC nomenclature of organic compounds. Electronic displacements in a covalent bond: inductive effect, electromeric effect, resonance and hyper conjugation. Homolytic and heterolytic fission of a covalent bond: free radicals, carbocations, carbanions, electrophiles and nucleophiles, types of organic reactions.

UNIT IX – Hydrocarbons

Classification of Hydrocarbons
Aliphatic Hydrocarbons:
Alkanes – Nomenclature, isomerism, conformation (ethane only), physical properties, chemical reactions.
Alkenes – Nomenclature, structure of double bond (ethene), geometrical isomerism, physical properties, methods of preparation, chemical reactions: addition of hydrogen, halogen, water, hydrogen halides (Markovnikov’s addition and peroxide effect), ozonolysis, oxidation, mechanism of electrophilic addition.
Alkynes – Nomenclature, structure of triple bond (ethyne), physical properties, methods of preparation, chemical reactions: acidic character of alkynes, addition reaction of – hydrogen, halogens, hydrogen halides and water.

Aromatic Hydrocarbons:

Introduction, IUPAC nomenclature, benzene: resonance, aromaticity, chemical properties: mechanism of electrophilic substitution. Nitration, sulphonation, halogenation, Friedel Craft’s alkylation and acylation, directive influence of functional group in monosubstituted benzene. Carcinogenicity and toxicity.

To know the CBSE Syllabus for all the classes from 1 to 12, visit the Syllabus page of CBSE. Meanwhile, to get the Practical Syllabus of Class 11 Chemistry, read on to find out more about the syllabus and related information in this page.

CBSE Class 11 Chemistry Practical Syllabus with Marking Scheme

In Chemistry subject, practical also plays a vital role in improving their academic scores in the subject. The overall weightage of Chemistry practical mentioned in the CBSE Class 11 Chemistry syllabus is 30 marks. So, students must try their best to score well in practicals along with theory. It will help in increasing their overall academic score.

CBSE Class 11 Chemistry Practical Syllabus

The experiments will be conducted under the supervision of subject teacher. CBSE Chemistry Practicals is for 30 marks. This contribute to the overall practical marks for the subject.

The table below consists of evaluation scheme of practical exams.

CBSE Syllabus for Class 11 Chemistry Practical

Micro-chemical methods are available for several of the practical experiments. Wherever possible such techniques should be used.

A. Basic Laboratory Techniques
1. Cutting glass tube and glass rod
2. Bending a glass tube
3. Drawing out a glass jet
4. Boring a cork

B. Characterization and Purification of Chemical Substances
1. Determination of melting point of an organic compound.
2. Determination of boiling point of an organic compound.
3. Crystallization of impure sample of any one of the following: Alum, Copper Sulphate, Benzoic Acid.

C. Experiments based on pH

1. Any one of the following experiments:

• Determination of pH of some solutions obtained from fruit juices, solution of known and varied concentrations of acids, bases and salts using pH paper or universal indicator.
• Comparing the pH of solutions of strong and weak acids of same concentration.
• Study the pH change in the titration of a strong base using universal indicator.

2. Study the pH change by common-ion in case of weak acids and weak bases.

D. Chemical Equilibrium
One of the following experiments:

1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing the concentration of either of the ions.
2. Study the shift in equilibrium between [Co(H₂O)₆] ²⁺ and chloride ions by changing the concentration of either of the ions.

E. Quantitative Estimation
i. Using a mechanical balance/electronic balance.
ii. Preparation of standard solution of Oxalic acid.
iii. Determination of strength of a given solution of Sodium hydroxide by titrating it against standard solution of Oxalic acid.
iv. Preparation of standard solution of Sodium carbonate.
v. Determination of strength of a given solution of hydrochloric acid by titrating it against standard Sodium Carbonatesolution.

F. Qualitative Analysis
1) Determination of one anion and one cation in a given salt
Cations‐ Pb²⁺, Cu²⁺, As³⁺, Al³⁺, Fe³⁺, Mn²⁺, Ni²⁺, Zn²⁺, Co²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mg²⁺, NH₄ ⁺
Anions – (CO₃)^2‐ , S^2‐, NO₂^‐ , SO₃^2‐, SO^2‐ , NO ^‐ , Cl^‐ , Br^‐, I‐, PO₄^3‐ , C₂O²‐ ,CH₃COO^‐
(Note: Insoluble salts excluded)

2) Detection of ‐ Nitrogen, Sulphur, Chlorine in organic compounds.

G) PROJECTS
Scientific investigations involving laboratory testing and collecting information from other sources.

A few suggested projects are as follows:

• Checking the bacterial contamination in drinking water by testing sulphide ion
• Study of the methods of purification of water.
• Testing the hardness, presence of Iron, Fluoride, Chloride, etc., depending upon the regional
  variation in drinking water and study of causes of presence of these ions above permissible
  limit (if any).
• Investigation of the foaming capacity of different washing soaps and the effect of addition of
  Sodium carbonate on it.
• Study the acidity of different samples of tea leaves.
• Determination of the rate of evaporation of different liquids Study the effect of acids and
  bases on the tensile strength of fibres.
• Study of acidity of fruit and vegetable juices.

Note: Any other investigatory project, which involves about 10 periods of work, can be chosen with the approval of the teacher.

Practical Examination for Visually Impaired Students of Class 11

Below is a list of practicals for the visually impaired students.

A. List of apparatus for identification for assessment in practicals (All experiments)
Beaker, tripod stand, wire gauze, glass rod, funnel, filter paper, Bunsen burner, test tube, test tube stand,
dropper, test tube holder, ignition tube, china dish, tongs, standard flask, pipette, burette, conical flask, clamp
stand, dropper, wash bottle
• Odour detection in qualitative analysis
• Procedure/Setup of the apparatus

B. List of Experiments A. Characterization and Purification of Chemical Substances
1. Crystallization of an impure sample of any one of the following: copper sulphate, benzoic acid
B. Experiments based on pH
1. Determination of pH of some solutions obtained from fruit juices, solutions of known and varied
concentrations of acids, bases and salts using pH paper
2. Comparing the pH of solutions of strong and weak acids of same concentration.

C. Chemical Equilibrium
1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing
the concentration of eitherions.
2. Study the shift in equilibrium between [Co(H2O)6]2+ and chloride ions by changing the
concentration of either of the ions.

D. Quantitative estimation
1. Preparation of standard solution of oxalic acid.
2. Determination of molarity of a given solution of sodium hydroxide by titrating it against standard
solution of oxalic acid.

E. Qualitative Analysis
1. Determination of one anion and one cation in a given salt
2. Cations – NH+4
Anions – (CO3)2-, S2-, (SO3)2-, Cl-, CH3COO-
(Note: insoluble salts excluded)
3. Detection of Nitrogen in the given organic compound.
4. Detection of Halogen in the given organic compound.

Note: The above practicals may be carried out in an experiential manner rather than recording observations.

We hope students must have found this information on CBSE Syllabus useful for their studying Chemistry. Learn Maths & Science in interactive and fun loving ways with ANAND CLASSES (A School Of Competitions) App/Tablet.

Frequently Asked Questions on CBSE Class 11 Chemistry Syllabus

Q1

How many units are in the CBSE Class 11 Chemistry Syllabus?

There are 9 units in the CBSE Class 11 Chemistry Syllabus. Students can access various study materials for the chapters mentioned in this article for free at ANAND CLASSES (A School Of Competitions).

Q2

What is the total marks for practicals examination as per the CBSE Class 11 Chemistry Syllabus?

The total marks for the practicals as per the CBSE Class 11 Chemistry Syllabus is 30. It includes volumetric analysis, content-based experiment, salt analysis, class record, project work and viva.

Q3

Which chapter carries more weightage as per the CBSE Syllabus for Class 11 Chemistry?

The organic chemistry chapter carries more weightage as per the CBSE Syllabus for Class 11 Chemistry.