Acids and bases are popular chemicals which interact with each other resulting in the formation of salt and water. The word acid comes from a Latin word ‘acere’ which means ‘sour’.
Table of Contents
In our everyday lives, we use many compounds which scientists call acids. The orange or grapefruit juice you drink for breakfast contains citric acid (also known as Vitamin C). When milk turns sour, it contains lactic acid. The vinegar used in salad dressing contains acetic acid. According to this, a chemical bond is considered as being made up of an acid-base combination. The properties of a molecule, therefore, can be understood by dividing it into acid and base fragments.
Acids and Bases Definition
An acid is any hydrogen-containing substance that is capable of donating a proton (hydrogen ion) to another substance. A base is a molecule or ion able to accept a hydrogen ion from an acid.
Acidic substances are usually identified by their sour taste. An acid is basically a molecule which can donate an H+ ion and can remain energetically favourable after a loss of H+. Acids are known to turn blue litmus red.
Bases, on the other hand, are characterized by a bitter taste and a slippery texture. A base that can be dissolved in water is referred to as an alkali. When these substances chemically react with acids, they yield salts. Bases are known to turn red litmus blue.
Acid Definition Chemistry
The terms acid and base have been defined in different ways, depending on the particular way of looking at the properties of acidity and basicity. Arrhenius first defined acids as compounds which ionize to produce hydrogen ions, and bases as compounds which ionize to produce hydroxide ions. According to the Lowry-Bronsted definition, an acid is a proton donor and a base is a proton acceptor.
According to the Lewis definition, acids are molecules or ions capable of coordinating with unshared electron pairs, and bases are molecules or ions having unshared electron pairs available for sharing with acids. To be acidic in the Lewis sense, a molecule must be electron deficient. This is the most general acid base concept. All Lowery Bronstead acids are Lewis acids but, in addition, the Lewis definition includes many other reagents such as boron trifluoride, aluminium chloride, etc.
Theories of Acids and Bases
Three different theories have been put forth in order to define acids and bases. These theories include the Arrhenius theory, the Bronsted-Lowry theory, and the Lewis theory of acids and bases. A brief description of each of these theories is provided in this subsection. Acids and bases can be defined via three different theories.
The Arrhenius theory of acids and bases states that “an acid generates H+ ions in a solution whereas a base produces an OH– ion in its solution”.
The Bronsted-Lowry theory defines “an acid as a proton donor and a base as a proton acceptor”.
Finally, the Lewis definition of acids and bases describes “acids as electron-pair acceptors and bases as electron-pair donors”.
pH of Acids and Bases
In order to find the numeric value of the level of acidity or basicity of a substance, the pH scale (wherein pH stands for ‘potential of hydrogen’) can be used. The pH scale is the most common and trusted way to measure how acidic or basic a substance is. A pH scale measure can vary from 0 to 14, where 0 is the most acidic and 14 is the most basic a substance can be.
Another way to check if a substance is acidic or basic is to use litmus paper. There are two types of litmus paper available that can be used to identify acids and bases – red litmus paper and blue litmus paper. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions.
Litmus Test of Acids and Bases
Properties of Acids and Bases
1. Properties of Acids
Acids are corrosive in nature.
They are good conductors of electricity.
Their pH values are always less than 7.
When reacted with metals, these substances produce hydrogen gas.
Some properties, like a bitter taste, are owned by all bases. The bases feel slippery, too. Dream on what slippery soap looks like. And this is a foundation. Furthermore, when immersed in water, bases conduct electricity because they consist of charged particles in the solution.
They are found to have a soapy texture when touched.
These substances release hydroxide ions (OH– ions) when dissolved in water.
In their aqueous solutions, bases act as good conductors of electricity.
The pH values corresponding to bases are always greater than 7.
Bases are bitter-tasting substances which have the ability to turn red litmus paper blue.
The neutral substance is a substance which is not acidic or basic, has the same amount of hydrogen and hydroxyl ions, and does not alter the colour of the litmus surface.
These substances do not display any acidic or basic characteristics.
Their pH values approximate to 7.
Neutral substances have no effect on red or blue litmus paper.
The pH of pure water is exactly 7.
Examples: Water, Common salt (NaCl)
Difference between Acids and Bases
Acids
Bases
Acid gives off hydrogen ions when dissolved in water.
Bases give off hydroxyl ion when dissolved in water.
It turns blue colour litmus paper into red.
It turns red colour litmus paper into blue.
It has a sour taste.
It has bitter taste and soapy to touch.
Its pH value ranges from 1 to 7.
Its pH value ranges from 7 to 14.
Example: HCl, H2SO4 etc.
Example: NaOH, KOH etc.
Arrhenius Concept of Acids and Bases
The Swedish scientist Svante August Arrhenius defined acids as substances that increase the H+ ion concentration of water when dissolved in it.
These protons go on to form hydronium ions (H3O+) by combining with water molecules.
Similarly, the Arrhenius definition of a base states that bases are the substances that, when dissolved in water, increase the concentration of OH– ions in it.
One of the merits of this theory is that it successfully explains the reaction between acids and bases that yield salts and water.
An important limitation of the Arrhenius definitions of acids and bases is that it fails to explain how substances lacking hydroxide ions form basic solutions when dissolved in water, such as NO2– and F–.
Bronsted Lowry Theory of Acids and Bases
The Bronsted-Lowry theory defines an acid as a donor of protons.
A base is defined as a proton acceptor (or H+ ion acceptor) by this theory.
Bronsted acids undergo dissociation to yield protons and therefore increase the concentration of H+ ions in the solution.
On the other hand, Bronsted bases accept protons from water (the solvent) to yield hydroxide ions.
An advantage of the Bronsted-Lowry definition of acids and bases is its ability to explain the acidic or basic nature of ionic species.
An important limitation of this theory is that it fails to explain how compounds lacking hydrogen exhibit acidic properties, such as BF3 and AlCl3.
Conjugate Acids and Bases
According to Bronsted-Lowry concept, an acid is a substance that can donate H+ and base is a substance that can accept H+.
The acid and base which differ by proton , are said to form conjugate acid and base pair.
A conjugate acid is formed when a proton is added to a base, and a conjugate base is formed when a proton is removed from an acid.
Examples: Consider the following reaction,
CH3COOH + H2O ⇋ CH3COO– + H3O+
In this above equation Acid: CH3COOH , Conjugate Base : CH3COO–
Base: H2O , Conjugate Acid: H3O+
Note: Conjugate Acid form by adding H+ ion on base, Conjugate base form by removing H+ ion from acid. (a) The conjugate base of H2PO4– is H2PO4– – H+ ⇋ HPO42- The conjugate base of H2PO4– is HPO42-
Lewis Concept of Acids and Bases
The Lewis definition of an acid states that it is a species that has a vacant orbital and therefore, has the ability to accept an electron pair.
A Lewis base is a species that holds a lone pair of electrons and can, therefore, act as an electron-pair donor.
This theory does not involve the hydrogen atom in its definition of acids and bases.
Lewis acids are electrophilic in nature whereas Lewis Bases possess nucleophilic qualities.
Examples of Lewis acids: Cu2+, BF3, and Fe3+. Examples of Lewis bases: F–, NH3, and C2H4 (ethylene).
A Lewis acid accepts an electron pair from a Lewis base, forming a coordinate covalent bond in the process. The resulting compound is referred to as a Lewis adduct.
A notable advantage of this concept is that many compounds can be defined as acids or bases by it. However, it offers little insight into the strength of these acids and bases.
One of the disadvantages of this theory is that it fails to explain the acid-base reactions that do not involve the formation of a coordinate covalent bond.
Uses of Acids and Bases
The various uses of acids and bases are listed in this subsection.
1. Uses of Acids
Vinegar, a diluted solution of acetic acid, has various household applications. It is primarily used as a food preservative.
Citric acid is an integral part of lemon juice and orange juice. It can also be used in the preservation of food.
Sulphuric acid acid is widely used in batteries. The batteries used to start the engines of automobiles commonly contain this acid.
The industrial production of explosives, dyes, paints, and fertilizers involves the use of sulphuric acid acid and nitric acid.
Phosphoric acid is a key ingredient in many soft drinks.
2. Uses of Bases
The manufacturing of soap and paper involves the use of sodium hydroxide. NaOH is also used in the manufacture of rayon.
Ca(OH)2, also known as slaked lime or calcium hydroxide, is used to manufacture bleaching powder.
Dry mixes used in painting or decoration are made with the help of calcium hydroxide.
Magnesium hydroxide, also known as milk of magnesia, is commonly used as a laxative. It also reduces any excess acidity in the human stomach and is, therefore, used as an antacid.
Ammonium hydroxide is a very important reagent used in laboratories.
Any excess acidity in soils can be neutralized by employing slaked lime.
Frequently Asked Questions – FAQs
Q1
How do you identify acids and bases?
To decide whether a substance is an acid or base, count the hydrogens on each substance before and after the reaction. If the number has decreased that substance is the acid (which donates hydrogen ions) . If the number of hydrogens has increased that substance is the base (accepts hydrogen ions)
Q2
What makes something an acid or a base?
An acid is a contributing product containing hydrogen ions. If the solution contains more hydronium ions (H3O+) than hydroxyl ions (OH-) , then the given solution is a acid. Similarly, if the solution contains more hydroxyl ions (OH-) than hydrogen ions (H+) , then the given solution is a base.
Q3
What is base and example?
The sodium hydroxide, calcium carbonate and potassium oxide are examples of bases. A base is a material that interacts with hydrogen ions and can neutralize the acid. Bases are classified as acceptors of a proton (H+), and ammonium hydroxide are typical examples of the bases.
Q4
What is an acid and its properties?
Acids are ionic compounds that, when dissolved in water, produce positive hydrogen ions ( H+) When dissolved in water, acids are sour in taste, conduct electricity and react with metals to produce hydrogen gas. Certain indicator compounds may be used to detect acids, such as litmus. Acids turn blue litmus red.
Q5
What is the main difference between an acid and a base?
Two types of corrosive compounds are the acids and bases. Any material with a pH value between 0 and 7 is known to be acidic while a pH value between 7 and 14 is a base. whereas, bases are ionic compounds that produce hydroxide ions(OH-) when dissolved in water.
Q6
What is the importance of acid?
Acids play significant roles within the human body. The presence of hydrochloric acid in the stomach helps digestion by breaking down large and complex food molecules. Amino acids are required for protein synthesis which helps to grow and repair body tissues.
Q7
What is base and example?
The sodium hydroxide, calcium carbonate and potassium oxide are examples of bases. A base is a substance that reacts with hydrogen ions and can neutralize the acid. Most bases are minerals which form water and salts by reacting with acids. Bases include the metal oxides, hydroxides, and carbonates.
Q8
How do you identify a base?
To decide whether a substance is an acid or base, count the hydrogens on each substance before and after the reaction. If the number has decreased that substance is the acid (which donates hydrogen ions) . If the number of hydrogens has increased that substance is the base (accepts hydrogen ions).
Q9
What are the physical properties of the base?
Base taste bitter has a soapy texture and releases hydroxide ions when dissolved in water. They are good conductors of electricity and have a pH value of more than seven. Sodium hydroxide, potassium hydroxide and magnesium hydroxide are some examples of bases.
Q10
Can acid react with metals?
Yes, acids do react with the metal to form the corresponding salt and liberate hydrogen gas. 2 M + 2 HX → 2 MX + H2
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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