During a chemical process, chemical equilibrium refers to the state in which the concentrations of both reactants and products have no tendency to fluctuate over time.
When the forward and reverse reaction rates are equal, a chemical reaction is said to be in chemical equilibrium. The state is known as a dynamic equilibrium, and the rate constant is known as the equilibrium constant, because the rates are equal and there is no net change in the concentrations of the reactants and products. Let’s look into it more.
Consider the universal reversible reaction: A + B ⇌ C + D.
At the beginning (i.e., at time t = 0), the absorption of A and B are consummate and the absorption of C and D are minimal ( equal to zero because no C and D are ultimately formed). As the reaction proceeds, the attention of A and B are reduced with time whereas the attention of C and D are added. Thus, the rate of advancing reaction is dwindling while the rate of backward reaction goes on adding.
Eventually, a stage comes, when the rate of encouraging response becomes equal to the rate of backward reaction. The reaction is also said to be in a state of chemical equilibrium. The interpretation of the reaction rates with time and eventually the accomplishment of chemical equilibrium may be represented diagrammatically.
The succeeding exemplifications illustrate how the equilibrium is achieved:
Decomposition of Calcium carbonate in a closed vessel,
Decomposition of N2O4 in a closed vessel,
Combination of H2 and I2 to form HI, and
Reaction between ferric nitrate and potassium thiocyanate solution.
Table of Contents
Law of Chemical Equilibrium
The Law of Chemical Equilibrium is a result obtained by applying the Law of Mass Action to a reversible reaction in equilibrium. For example, consider the general reversible reaction,
A + B ⇌ C + D
At equilibrium, assume the active masses of A, B, C and D are represented as [A], [B], [C], and [D] respectively. Applying the Law of Mass Action,
The rate at which A and B react together, i.e.
Rate of the forward reaction ∝ [A] [B] = kf[A] [B]
where kf could be a constant of proportionality and is termed velocity constant for the forward reaction.
Similarly, the rate at which C and D react together, i.e.,
Rate of the backward reaction ∝ [C] [D]= kb[C] [D]
where kb represents the velocity constant for the backward reaction.
At equilibrium,
Rate of forward reaction = Rate of backward reaction
Hence,
kf[A][B] = kb[C][D] or ([C][D])/([A][B]) = kf/kb = K
At constant temperature, as kf and kb are constant, therefore, kf/ kb = K is also constant at constant temperature and is called Equilibrium constant.
Again, consider the furthermore universal reversible reaction.
productions are written in the numerator and those
aA + bB +…… ⇌ xX+yY + …
Applying the Law of Mass Action, as before, we get
[X]x [Y]y/[A]a[B]b = K or Kc
where K is the equilibrium constant. It’s constant at stationary temperature.
Equilibrium Constant
The aforementioned mathematical equation is called the Law of Chemical Equilibrium. stated in words, it may be outlined as follows-
The product of the molar concentrations of the products, each raised to the power adequate to its stoichiometric coefficient divided by the product of the molar concentrations of the reactants, each raised to the power adequate to its stoichiometric coefficient is constant at constant temperature and is termed as Equilibrium constant.
It’s conventional to use K. for equilibrium constant raised in terms of concentrations. Where there’s no distrustfulness that K is in terms of concentration, c is neglected.
For gas-phase reactions, (that is when the reactants and products are gaseous), the equilibrium constant can be expressed either as concentrations in moles per litre or in terms of the partial pressures of the reactants and products. if stated in terms of partial pressures. However, it is denoted by Kp so, if A, B, X, and Y are gaseous, it can be-
KP = (PXx. PYy)/(PAa. PBb)
Where PA PB, PX, and PY are the partial pressures of A, B, X, and Y independently in the reaction amalgam at equilibrium. It may be observed that the pressures in the aforementioned equation are grasped in atmospheres or bars or pascals (in SI units).
Characteristics of Equilibrium Constant
Some of the most consequential characteristics of the Equilibrium constant are as follows:
The value of the Equilibrium constant for an individual reaction is always constant hinging exclusively upon the temperature of the reaction and is self-subsistent of the concentrations of the reactions with which we start or the direction from the Equilibrium is came up.
If the value of the Equilibrium constant is inversed If the reaction is switched.
Nevertheless, the Equilibrium constant for the substitute equation is the quadrate root of K(that is √K), If the equation is divided by 2.
The Equilibrium constant for the new equation is the square of K(that is K2) If the equation is multiplied by 2.
If the equation is scratched in two steps also K1 × K2 = K.
The value of the Equilibrium constant isn’t affected by the extension of the catalyst to the reaction.
Effect of Temperature on Equilibrium Constant
The numerical value of the equilibrium constant for an individual reaction is stable as long as its temperature is commemorated stable. It’s a well-understood reality that the rate of a chemical reaction increases with an increase in temperature.
Still, the termination of this rate increase depends upon the energy of activation of the reaction. anymore, since the energy of activation for the forward and backward reactions are disparate, so a presented increment in temperature will increase the rate of the forward and backward reactions to different extents. Indistinguishable terms, the values of the velocity constants for forwarding and backward responses. i.e, kb and will change else with a given rise or fall in temperature.
Further, since K = kf/kb thus, the value of the equilibrium constant (K) will change, i.e. the state of equilibrium is altered. Therefore, we conclude that the equilibrium constant for individual reaction fluctuations with temperature. Further, it has been found that the value of the equilibrium constant of an endothermic reaction increases (kf increases more than kb) and that of an exothermic reaction diminishments (kb increases additional than kf) with elevation in temperature. For reactions having zero heat of reaction, the temperature has no aftereffect on the value of K.
Factors Affecting Equilibrium
Change of concentration of any product or reactant
Change of temperature of the system
Change the pressure of the system
Addition of catalyst
Addition of inert gas.
Splved Problems
Problem 1: At 773 K, the equilibrium constant Kc for the reaction, N₂ (g) + 3 H₂ (g) ⇌ 2 NH3 (g) is 6.02 x 10-2 L² mol–². Calculate the value of Kp at the same temperature.
Problem 2: For the equilibrium, 2 NOCI (g) ⇌ 2 NO(g) + Cl₂ (g), the value of the equilibrium constant, Kc is 3.75 x 10-6 at 1069 K. Calculate Kp for the reaction at this temperature.
Solution:
△n=(2+1)-2= 1
Kp= Kc(RT)△n = (3.75 × 10-6 )(0.0831 × 1069)
= 3.33 × 10-4
Problem 3: The following concentrations were obtained for the formation of NH3 from N2 and H2 at equilibrium at 500 K: [N2]=1.5× 10-2 M, [H2] = 3.0 x 10-2 × M and [NH3] = 1.2 × 10-2 M.
Solution:
The equilibrium reaction is :N2 (g)+3H2 (g) ⇌ 2NH3 (g)
Kc = [NH3]2/[N2][H2]3
= (1.2 × 10-2 )2 /(1.5 × 10-2 )(3.0 × 10-2 )3
= 3.55 × 102
Problem 4: For an equilibrium reaction, the rate constants for the forward and the backward reaction are 2.38 x10-4 and 8.15 x 10-5 respectively. Calculate the equilibrium constant for the reaction.
Solution:
Equilibrium Constant K= kf /kb = (2.38 x 10-4 )/(8.15×10-8)=2.92
Problem 5: The value of K, for the reaction, 2 AB + C is 2.0 × 10³ At a given time, the composition of the reaction mixture is [A] = [B] = [C] = 3 × 10.4 M In which direction, the reaction will proceed?
Solution:
For the given reaction. Qc = [B][C]/[A]2
= (3 x 10-4)(3 x 10-4)/ (3 x 10-4)2 =1
Thus, Qc> Kc Hence, the reaction will proceed in the backward direction.
Problem 6: In the equilibrium, CaCO3 (s) ⇌ CaO (s) + CO₂ (g), at 1073 K, the pressure of CO₂ is found to be 2.5 x 10 Pa. What is the equilibrium constant of this reaction at 1073 K?
Solution:
With reference to the standard state pressure of 1 bar, i.e., 105 Pa,
Kp = pCO₂ = 2.5 ×104 Pa/p0
= (2.5 × 104 Pa)/105 Pa
= 0.25
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.
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.
Evaluation Scheme
Marks
Volumetric Analysis
08
Salt Analysis
08
Content Based Experiment
06
Project Work
04
Class record and viva
04
Total
30
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‐ , S2‐, NO2‐ , SO32‐, SO2‐ , NO ‐ , Cl‐ , Br‐, I‐, PO43‐ , 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 theapproval 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.
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