Chemical equilibrium is the state of a system in which the reactant and product concentrations do not change over time and the system’s attributes do not change further.
Reactions take place in both forward and reverse directions. When the rates of the forward and reverse reactions are similar in such processes, the concentrations of the reactants and products stay constant.
The reaction is said to be in chemical equilibrium at this point. This equilibrium, on the other hand, is thought to be dynamic in nature.
This is due to the fact that it comprises a forward reaction in which the reactants react to produce products and a reverse reaction in which the products can react to produce the original reactants.
Why is Chemical Equilibrium called Dynamic Equilibrium?
An equilibrium stage is defined as the point at which the rate of forwarding reaction equals the rate of backward response. The number of reactant molecules changing into products and product molecules converting into reactants is the same at this moment. The same equilibrium can be achieved with the same reactants under comparable conditions anywhere in the world, implying that chemical equilibrium is dynamic.
Dynamic Nature of Chemical Processes in Equilibrium
Take a look at the following reversible reaction–
A + B ⇌ C + D
The products (C and D) build with time, whereas the reactants (A and B) diminish. As a result, the rate of forwarding reaction decreases while the rate of reverse reaction increases. Finally, both reactions take place at the same moment, resulting in a state of equilibrium. This balance can be attained from either direction.
Haber’s Process
Fritz Haber, a German chemist, invented a method for producing ammonia from dinitrogen and dihydrogen. This is known as the Haber process.
N2(g) + 3H2(g) ⇌ 2NH3(g)
Haber began with known proportions of dinitrogen and dihydrogen, kept the mixture at high temperature and pressure, and measured the amount of ammonia generated at regular intervals. As the reaction progressed, he saw that the composition of the mixture remained constant, despite the presence of some reactants. This indicates that the reaction has achieved equilibrium.
In addition, Haber’s method exemplifies the dynamic character of chemical equilibrium in the following way. Maintaining the same experimental settings as before, hydrogen was substituted with deuterium (D2).
As a result, instead of NH3, ND3 is produced. Both reactions, one using H2 and the other involving D2, were allowed to reach equilibrium. When these two mixtures were mixed and left for a while, the concentration of ammonia was found to be the same as previously.
Despite this, mass spectrometry confirmed that, in addition to ammonia, all types of deuterium and dihydrogen were present.
Because the forward and reverse processes continue, the scrambling of H and D atoms must be conceivable. If the reaction had ended when it reached equilibrium, there would have been no mixing of isotopes. As a result, chemical reactions attain a state of dynamic equilibrium in which the rates of forwarding and reverse reactions are equal and no net change in composition occurs.
Chemical Equilibrium is Bidirectional
Whether we begin a reaction with reactants or products, equilibrium can be reached on both sides. Take a look at the following reaction.
H2(g) + I2(g) ⇌ 2HI(g)
If we start the reaction with equal initial concentrations of H2 and I2, the reaction will go forward, with the concentrations of hydrogen and iodine decreasing and the concentration of hydrogen iodide increasing until it achieves equilibrium. If we reverse the above reaction, the concentration of hydrogen iodide falls while the concentrations of hydrogen and iodine grow until equilibrium is reached. As a result, if the total number of atoms of an element in a given volume is the same, we get the same equilibrium mixture whether we start with reactants or products.
Conditions for Equilibrium
The process of achieving chemical equilibrium is a dynamic one. Even after the equilibrium state is reached, the forward and reverse processes continue to occur. However, the speeds of the reactions are the same in this case, and there is no change in the relative concentrations of reactants and products for an equilibrium reaction. The following are the criteria and properties of an equilibrium system.
The system must be closed, which means that no substances may enter or exit it.
Equilibrium is a living, breathing thing. Even if we cannot see the reactions, both forward and reverse reactions are occurring.
The rates of forwarding and backward reactions must be equal.
The number of reactants and products does not have to be the same. However, once equilibrium is reached, the amounts of reactants and products remain constant.
Examples of Chemical Equilibrium
The forward reaction in chemical reactions converts reactants into products, whereas the backward reaction converts products back into reactants. There are two states, reactants and products, and they both exist in different compositions.
When the reaction begins, the rates of the forward and backward responses may become equal after some time.
Following this, the number of reactants converted will be created again by the reverse reaction, resulting in no change in the concentration of reactants and products. As a result, the reactants and products will be in a state of chemical equilibrium.
FAQs
Question 1: What Happens at Chemical Equilibrium?
Answer:
The pace of advance and backward reactions becomes equal at the chemical equilibrium state, and the concentrations of products and reactants remain constant. During a reversible chemical process, chemical equilibrium occurs when there is no net change in the proportions of reactants and products. Reversible chemical reactions occur when the products, after they have been generated, react with the initial reactants to make the products. In equilibrium, both opposing processes occur at the same rate or velocity, and the quantity of substances involved do not change. In equilibrium, both opposing processes occur at the same rate or velocity, and the quantity of substances involved do not change.
Question 2: What Happens after Equilibrium is Reached?
Answer:
When equilibrium is attained, solution particles will continue to travel over the membrane in both directions. Despite the fact that nearly an equal number of particles flow in each direction, there is no further change in concentration. Equilibrium is the state of a reversible reaction in which the forward reaction rate matches the backward reaction rate. The reaction does not thereafter come to a halt. Because dissolution is a reversible process, if we add sugar to water indefinitely, we will eventually be unable to add more, but this does not mean that the sugar being added is not being dissolved in water; it is simply the concept of Equilibrium at that time.
Question 3: What is Lechatelier’s principle?
Answer:
According to Lechatelier’s principle, any changes in the components impacting the equilibrium condition will offset or lessen the total transformation effect. This rule holds true for both chemical and physical equilibrium.
Question 4: What Happens to Equilibrium When the Product is Removed?
Answer:
If we remove a reactant or product from the equilibrium state, the equilibrium shifts to produce more reactant or product, respectively, to compensate for the loss. When a product is removed from a chemically balanced system, the equilibrium shifts to produce more products in order to compensate for the loss in product concentration. In contrast, removing a reactant causes the system’s equilibrium to shift, allowing more reactants to be created.
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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