Figuring out the ratios in which different substances or elements react to one another. The laws of conservation of mass, energy, and weights or volumes serve as the foundation for the rules used to determine stoichiometric relationships.
Chemical Stoichiometry refers to the quantitative study of the reactants and products involved in a chemical reaction. The word “stoichiometry” is derived from the Greek word “stoikhein” meaning element, and “metron” meaning measure.
The term Stoichiometry was first coined or discovered by a German chemist named Jeremias Richter. Even though this tongue-twisting word can sound complicated and big, it is a simple idea. In this lesson, we will learn about what it means and discuss the different aspects of this concept.
Table of Contents
What Is Stoichiometry?
In simple words, we can define,
Stoichiometry as the calculation of products and reactants in a chemical reaction. It is basically concerned with numbers.
Stoichiometry is an important concept in Chemistry that helps us use balanced chemical equations to calculate amounts of reactants and products. Here, we make use of ratios from the balanced equation. In general, all the reactions that take place are dependent on one main factor, that is, how much substance is present.
Stoichiometry helps us determine how much substance is needed or is present. Things that can be measured are,
Reactants and products mass
Molecular weight
Chemical equations
Formulas
Stoichiometric Coefficient
The stoichiometric coefficient or stoichiometric number is the number of molecules that participate in the reaction. If you look at any balanced reaction, you can notice that there are an equal number of elements on both sides of the equation. The stoichiometric coefficient is basically the number present in front of atoms, molecules or ions.
Stoichiometric coefficients can be fractions as well as whole numbers. In essence, the coefficients help us to establish the mole ratio between reactants and products.
Balanced Reactions and Mole Ratios
Atoms and molecules are extremely small in size, and their numbers in a very small amount of a substance are very large. Therefore, to represent atoms and molecules in bulk, a mole concept was introduced. One mole of any substance contains 6.022 x 1023 numbers of that substance. This number is also known as Avogadro’s number.
The mass of one mole of a substance in grams is called molar mass.The molar mass of one mole of a substance is numerically equal to the atomic/molecular formula mass.
Let us take one example of a balanced chemical equation,
3Fe(s) + 4H2O(l) ⇾ Fe3O4 (s)+ 4H2 (g)
The quantitative information drawn from this balanced chemical equation is
3 mole of Fe reacts with 4 moles of H2O to yield one mole of Fe3O4 and 4 moles of H2.
168g ( 56×3) of Fe reacts with 72g( 18×4) of H20 to yield 231g of Fe3O4 and 8g of H2 gas.
If the reactants and products are in gaseous form, then the molar volume is taken into consideration. One mole of any gas occupies 22.4 litres.
CH4(g) + 2O2(g)⇾ CO2(g)+ 2H20 (g)
In the above reaction, 22.4 litres of CH4 reacts with 44.8 (2 x 22.4) litres of 02 to yield 22.4 litres of CO2 and 44.8 litres of H2O.
Limiting Reagent
In a chemical reaction, it is possible that one of the reactants is present in excess amount. Some of these excess reactants will, therefore, be left over when the reaction is complete; the reaction stops immediately as soon as one of the reactants is totally consumed.
The substance that is totally consumed in a reaction is called the limiting reagent.
Let us take one example of a chemical reaction to understand the limiting reagent concept.
N2 + 3H2 ➝ 2NH3
Suppose we have one mole of N2 reacting with one mole of H2. But from the balanced chemical equation, one mole of N2 requires three moles of H2. So, the limiting reagent in this reaction is H2.
Stoichiometry in Chemical Analysis
Stoichiometric calculations, which follow a quantitative analysis methodology, are often used by chemists to determine the concentrations of substances present in a sample. There are basically two main types of analysis, and we will discuss them below.
1. Gravimetric Analysis
In Analytical Chemistry, gravimetric analysis describes the quantitative determination of an analyte based on the mass of the solid. The gravimetric analysis gives the most accurate results out of all other analytical analyses, as the weight of a substance can be measured with great accuracy compared to other fundamental quantities.
Gravimetric analysis can be classified into the following types:
Precipitation gravimetry – It involves the isolation of ions in solution by a precipitation reaction, filtering, washing the precipitate free of contaminants, and finally weighing the precipitate and determining its mass by difference.
Volatilization gravimetry – Volatilization gravimetry involves separating components of a mixture by heating or chemically decomposing the sample.
Electrogravimetry – It involves the electrochemical reduction of metal ions at the cathode and the simultaneous deposition of ions on the cathode. The cathode is weighed before and after electrolysis, and the weight difference corresponds to the mass of the analyte initially present in the sample.
2. Volumetric Analysis
The volumetric analysis involves the quantitative measurement of substance in terms of volume.
Principle: In volumetric analysis, a known volume (V1) of the substance, whose concentration (N1) is known, is reacted with the unknown volume (V2) of the solution of the substance, whose concentration (N2) is to be calculated. The volume V1 is noted at the endpoint of the reaction. The concentration N2 is calculated using the following equation.
N1x V1 = N2 x V2
The endpoint of such a reaction is indicated by a change in colour or precipitation etc.
Terms involved in volumetric analysis are as follows:
Titration – The process of finding out the volume of solution required to react completely with the volume of another solution is called titration.
Titrant – The solution of known strength is called titrant.
Titrate – The solution whose concentration is to be estimated is called titrate.
Indicator – Indicators are reagents which change their colour when the reaction is complete.
Stoichiometry Problems with Solutions
1. Calculate the mass of sodium hydroxide required to make 500 ml of 0.10 M solution.
Solution:
The molar mass of NaOH = 40g
Volume of NaOH = 500ml = 0.5 L
Molarity = 0.10M
Molarity = moles/volume in litres
⇒ weight of NaOH = molarity x molar mass of NaOH x volume
= 0.10 x 40 x 0.5
= 2 g
2. How much volume of 11 M HCl has to be diluted with water to prepare 3 M 400 ml HCl?
Solution:
M1 = 11M
M2 = 3M
V1 = ?
V2= 400ml
Now, M1 x V1= M2 x V2
⇒V1= (3×400)/ 11
= 109 ml
3. How many carbon atoms are present in 0.5 moles of oxalic acid (C2H2O4)?
Solution :
1 mole of oxalic acid = 6.022 x 10 23 number of oxalic acid
0.5 mole of oxalic acid = 6.022 x 10 23 x 0.5 number of oxalic acid
Since there are 2 carbon per oxalic acid,
The number of carbon atoms in 0.5 moles of oxalic acid = 6.022 x 10 23 x 0.5 x 2
= 6.022 x 10 23
4. 0.5216g of a solid mixture containing Na2SO4 is dissolved in water and treated with an excess of BaCl2, resulting in the precipitation of 0.6168g of BaSO4. What percentage of the mixture was BaS04?
Solution:
Na2SO4 + BaCl2 → BaSO4 + 2NaCl
233g of BaSO4 is obtained from 142g of Na2SO4
So, 0.6168g of BaSO4 is obtained from = (142×0.6168) / 233
= 0.37g
Since the mass of the solid mixture is 0.5216 g,
The percentage of BaSO4 is solid mixture = (0.37/0.5216) x 100
= 70.34%
5. A solution containing 5 g of KOH and Ca(OH)2 is neutralised by an acid. If it consumes 0.3 g equivalents of the acid, calculate the composition of the solution.
Solution:
Let the mass of KOH present in mixture = x
Mass of Ca(OH)2 = (5-x)g
Equivalent mass of KOH = 56; Equivalent mass of Ca(OH)2 = 74/2
Gram equivalent of KOH + Gram equivalent of Ca(OH)2 = Gram equivalent of acid
+ = 0.1
⇒ x = 3.83g
Mass of KOH in the sample = 3.83g
Percentage of KOH = (3.83/5) x 100
= 76.6%
Percentage of Ca(OH)2 = x100
= 23.4%
Frequently Asked Questions – FAQs
Q1
What is the role of stoichiometry?
We can predict the amount of products from a chemical reaction according to stoichiometry. Stoichiometric calculations allow us to forecast the quantity of compounds formed in a chemical reaction given the amounts of the reactants.
Q2
What is a balanced chemical equation?
A balanced chemical equation is an equation where the number of atoms of each type in the reaction is the same on both reactants and product sides
Q3
What is stoichiometry with example?
Stoichiometry is often used to balance chemical equations.
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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