Some basic concepts of chemistry

50 Pages·2016·0.79 MB·English

For all Agricultural, Medical, Pharmacy and Engineering Entrance Examinations held across India.

JEE – Main & AIPMT
Chemistry

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• Exhaustive coverage of MCQs subtopic wise.

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  • Additional information relevant to the concepts.
  • Neat, labelled and authentic diagrams.
  • In all ‘3897’ MCQs including questions from various competitive exams.

• Hints provided wherever relevant.

• Simple and lucid language.

• Self evaluative in nature.

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TEID : 751
PREFACE 
Chemistry is one of the oldest academic discipline and its roots lie in man’s fascination towards study of structure,
composition and properties of matter and the reactions by which matter converts from one form to the other.

NEET: Chemistry (Vol. I) not only adds great value towards a progressive society but also contributes greatly to other
branches of science like biology, physics, geology, astronomy, biotechnology etc. Thus chemistry serves to be the backbone
of all lifesciences.

Target’s “NEET: Chemistry (Vol. I)” has been compiled according to the notified syllabus for NEET-UG & ISEET, which
in turn has been framed after reviewing various state syllabi as well as the ones prepared by CBSE, NCERT and COBSE.
In the National-Eligibility-cum-Entrance Test (NEET), 25% weightage is given to Chemistry, as there are 45 questions
based on Chemistry, out of the total 180 questions.

Target’s “NEET: Chemistry (Vol. I)” comprises of a comprehensive coverage of theoretical concepts & Multiple Choice
Questions. In the development of each chapter we have ensured the inclusion of shortcuts & unique points represented as a
‘note’ for the benefit of students.
The flow of content & MCQs have been planned keeping in mind the weightage given to a topic as per the NEET-UG &
ISEET exam.

MCQs in each chapter comprise of mixture of questions based on theory & numericals and their level of difficulty is at par with
that of various competitive examinations like CBSE, AIIMS, CPMT, PMT, JIPMER, IIT, AIEEE, & the likes.
This edition of “NEET: Chemistry (Vol. I)” has been conceptualized with a complete focus on the kind of assistance
students would require to answer tricky questions, which would give them an edge required to score in this highly
competitive exam.
Lastly, we are grateful to the publishers of this book for their persistent efforts, commitment to quality & their unending
support to bring out this book, without which it would have been difficult for us to partner with students in this journey
towards their success.
All the best to all Aspirants!
Yours faithfully
Authors

No. Topic Name Page No.
1 Some Basic Concepts of Chemistry 1
2 Structure of Atom 48
3 Classification of Elements and Periodicity in Properties 100
4 Chemical Bonding and Molecular Structure 132
5 States of Matter: Gases and Liquids 209
6 Thermodynamics 252
7 Equilibrium 307
8 Redox Reactions 384
9 Hydrogen 424
10 s-Block Elements (Alkali and Alkaline earth metals) 460
11 Some p-Block Elements 512
12 Organic Chemistry – Some Basic Principles and Techniques 565
13 Alkanes 655
14 Alkenes 693
15 Alkynes 727
16 Aromatic hydrocarbons 749
17 Environmental Chemistry 786
TARGET Publications Chemistry (Vol. I)
(cid:9)
0 1

Some basic concepts of chemistry

1.0 General Introduction – Importance and Scope of Chemistry

(cid:190) Scientists and their contribution:

Scientists Contribution
Joseph Louis Gay-Lussac Gay Lussac’s law of combining volumes of gases
Amedeo Avogadro Avogadro’s law
Antoine Lavoisier Law of conservation of mass
Joseph Proust Law of definite composition
John Dalton Law of multiple proportions

(cid:190) Chemistry:
“Chemistry is defined as the study of composition, structure and properties of matter and the
reactions by which one form of matter may be converted into another form.”

(cid:190) There are five important branches of chemistry such as:

CHEMISTRY

Physical Inorganic Organic Analytical
Bio-Chemistry
Chemistry Chemistry Chemistry Chemistry

It deals with the It deals with the It deals with It deals with the It deals with the

structure of matter, the chemistry of the chemistry separation, extraction, substances which

energy changes and elements other of carbon and identification and are constituents of

the theories, laws and than carbon and carbon quantitative living organisms.

principles that explain their compounds. compounds. determination of the

the transformation of composition of

matter from one form different substances.

to another.

Note:
Apart from the above, there are several other branches of chemistry as:
i. Medicinal (pharmaceutical) Chemistry: It deals with the application of chemical research
techniques to the synthesis of pharmaceuticals.
ii. Environmental Chemistry: It deals with the study of chemistry associated with soil, air and water
and also of the impact of human activities on the natural system.
iii. Green Chemistry: It deals with processes and products that eliminate or reduce the use or release of
hazardous substances.
iv. Food Chemistry: It deals with the chemical processes associated with all forms of food stuffs.
v. Agrochemistry: It deals with the application of chemistry for agricultural production and food
processing.
vi. Geo Chemistry: It deals with the study of chemical composition and chemical processes associated
with Earth and the other plants.
vii. Astrochemistry: It deals with the study of the compositions and reactions of the chemical elements
and molecules found in the space and the interactions between this matter and radiation.
viii. Photochemistry: It deals with the interactions between light and matter.

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ix. Electrochemistry: It deals with the study of chemical reactions in a solution and electron transfer
particularly within electrolytic solution.
x. Solid State Chemistry: It deals with the structures, properties and chemical processes that occur in
the solid phase.
xi. Polymer Chemistry: It deals with the examination of structure and properties of macromolecules and
the study of new ways to synthesize those molecules.
xii. Nuclear Chemistry: It deals with the study of radioactivity, nuclear processes and nuclear properties.
xiii. Nano Chemistry: It deals with the production and reactions of nanoparticles and their compounds.

(cid:190) Importance and scope of Chemistry:
Chemistry plays a very important role in our everyday lives. Our daily needs of food, clothing,
shelter, potable water, medicines, etc., are in one or the other manner connected with chemical
compounds, processes and principles. There is no aspect of life that is not associated with chemistry.
In fact, Chemistry is the single branch of science which profoundly influences the existence of human
beings, plants, animals as well as their habitat. Thus, mankind owes much to chemistry because it has
improved the quality of life.

(cid:190) Some Applications of Chemistry:
i. Chemistry in medicines and health care:
The chemical substances used for treatment of diseases by destroying the disease causing
agents (antigens) without causing harm to the host tissues are called drugs or medicines.
Some of the medicinal compounds are mentioned below:

NAME OF THE FUNCTION/MEDICINAL
EXAMPLES
COMPOUND PROPERTY
a. Antipyretics Used to lower the temperature of the Aspirin (acetylsalicyclic acid),
body in high fever. paracetamol, phenacetin
b. Analgesics Used to relieve pain without causing
impairment of consciousness. These are
of two types:
i. Narcotic drugs: These are sleep Naproxen, Ibuprofen
inducing.
ii. Non-narcotic drugs: These do not Morphine, Codeine
induce sleep.
c. Tranquillizers Used for the treatment of stress, fatigue, Noradrenaline, Iproniazid,
mild and severe mental diseases. Phenelzine (antidepressant
drugs)
d. Antiseptics Used to either kill or prevent the growth Furacin, Soframycin
of micro-organisms. Not harmful and
can be applied on living tissues.
e. Disinfectant Used to kill micro-organisms, but are Chlorine, Dettol, Bithional,
harmful to mankind and cannot be Iodine, Boric acid, Iodoform,
applied on living tissues. Hydrogen peroxide
f. Antimicrobials Used to cure infections caused by Salvarsan, prontosil
micro-organisms.
g. Antibiotics Produced by microbes and are used to Penicillin, Ampicillin,
inhibit the growth of microbes. Streptomycin, Neomycin
h. Antacids Used to neutralize excess acid in the Baking soda (NaHCO ) in
3
gastric juices and give relief from acid water, omeprazole,
indigestion, acidity and gastric ulcers. lansoprazole
i. Antihistamines Used to diminish or abolish the main Brompheniramine,
actions of histamine released in the (Diametapp), Terfenadine
body, thus prevent the allergic (Seldane), Dimithendine
reactions. (foristal)

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j. Anaesthetics Used to produce general or local General anaesthetics:
insensibility to pain and other Chloroform, Diethyl ethers,
sensations. Vinyl ethers.
Local anaesthetics:
Cocaine, Novocaine.
k. Antifertility Used to control pregnancy. Ethynylestradiol (Novestrol),
drugs Mifepristone

ii. Chemistry in food:
Many chemicals are added to food for their preservation and enhancing their appeal. These are
called food additives. While antioxidants, preservatives, fat emulsifiers, flour improvers are
added to increase the shelf life of the stored food, some additives like dyes, flavours and
sweetening agents are added to improve their cosmetic value. Some of these additives are
mentioned below:

NAME OF THE
FOOD FUNCTION EXAMPLES
ADDITIVE
a. Food preservatives These are added to the food materials to Butylated hydroxyanisole,
prevent their spoilage and to retain their (BHA), Butylated hydroxy
nutritive value for long periods. toluene (BHT)
b. Taste enhancers These are used to enhance the taste of Monosodium glutamate
food stuffs. (MSG) – commonly called
as aginomoto.
c. Artificial These give sweetening effect to the food Aspartame (methylester)
sweetening agents and enhance its odour and flavour. Alitame, sucralose.
d. Edible food These are used to give an attractive Natural dye like carotene.
colours (dyes) appeal to the food stuffs.

iii. Other applications of chemistry:
a. Fuel: These are used for transportation and power generation. Petroleum is a rich source
of organic compounds. It is fractionally distilled to obtain various fractions like gasoline,
kerosene, diesel and aviation fuel.
b. Dyes: These impart colour to the textiles. A dye should have a suitable colour and
capacity to fix to the fibre.
Natural dyes include Indigo, alizarin etc.
Synthetic dyes include Azo dyes, pthalocyanin dyes, etc.
c. Detergents: These are the substances which possess cleansing properties.
E.g. Sodium alkyl sulphates:
(C H – OSO Na: Sodium lauryl sulphate),
12 25 3
long chain alkyl benzene sulphonates:

C H SO Na
12 25 3

Sodium p-dodecyl benzene sulphonate.

(cid:190) Matter and its constituents:
i. The entire universe is made up of matter.
ii. Matter is anything which has mass and occupies space.
iii. It exists in three physical forms viz., solid, liquid and gas.
a. Solids have definite shape and definite volume.
b. Liquids have definite volume but no definite shape.
c. Gases have neither definite shape nor definite volume.
iv. These three states are interconvertible by changing the conditions of temperature and pressure.
Solid (cid:89)(cid:90)(cid:90)(cid:90)he(cid:90)a(cid:90)t(cid:88)(cid:90) Liquid (cid:89)(cid:90)(cid:90)(cid:90)he(cid:90)a(cid:90)t(cid:88)(cid:90) Gas
cool cool

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Note:
Greek philosopher Democritus had suggested that matter is composed of extremely small atomio.

(cid:190) Classification of matter:

Matter

Physical classification Chemical classification

Solids Liquids Gases
Eg. NaCl Eg. H2O Eg. CH4

Mixtures Pure substance
Physical methods

It comprises of two or more It comprises of a single type

substances (components) present in of particle present in a fixed

any ratio in which the constituent ratio in which all the

substances retain their separate constituent particles are

identities. Eg. Air, Tea, Brass (an same in their chemical

alloy of copper and zinc) etc nature. Eg. Water, glucose,

sodium chloride etc

Homogeneous Heterogeneous
It comprises of a single phase It comprises of two or more
in which components are phases present in the mixture
completely mixed with each and its composition is not
other and its composition is uniform throughout.
uniform throughout. Eg. Phenol-water system,
Eg. Mixture of salt and silver chloride-water
water. system etc.

Compounds Elements
Pure substances which are Pure substances which
Chemical methods
made up of two or more are made up of only one
components. component.
Eg. Water, ammonia, etc. Eg. Ag, Au, Cu, etc.

Inorganic Organic

Eg. AlCl Eg. CH CHO
3 3

(cid:190) Unit and its need:
Definition:
“The arbitrarily decided and universally accepted standards used in the measurement of physical
quantities are called units.”

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Need:
i. For calculation of experimental data.
ii. For measurement of physical quantities such as mass, pressure, volume, length, time,
temperature, density, etc.
iii. Any measured property is expressed as a number along with an appropriate unit associated with
the property as only the number does not give any idea of the property.

(cid:190) Various system in which units are expressed:
i. Units are expressed in various systems like CGS (centimeter for length, gram for mass and
second for time), FPS (foot, pound, second) and MKS (meter, kilogram, second) systems etc.
ii. In 1960, the general conference of weights and measures, proposed a revised metric system,
called International System of units i.e., SI system, abbreviated from its French name
Systeme Internationale d′ Units.

Note:
NASA’s Mars climate orbiter, the first weather satellite for Mars, was destroyed by heat. The failure
of the mission was due to confusion in estimating the distance between Earth and Mars in miles and
kilometers.

(cid:190) Seven fundamental SI units:

No. Fundamental quantity SI unit Symbol
1. Length Meter m
2. Mass Kilogram kg
3. Time Second s
4. Temperature Kelvin K
5. Amount of substance Mole mol
6. Electric current Ampere A
7. Luminous intensity Candela cd

(cid:190) Derived units
The units of all physical quantities can be derived from the seven fundamental SI units. These units
are known as derived units.
The table given below shows some common derived units.

No. Physical quantity Relationship with fundamental unit Symbol
i. Area Length squared m2
ii. Volume Length cubed m3
iii. Density Mass per unit volume kg m−3
iv. Velocity Distance travelled in unit time ms−1
v. Acceleration Velocity change per unit time ms−2
vi. Force Mass × acceleration kg m s−2 (newton, N)
vii. Pressure Force per unit area kg m −1 s−2
viii. Electric charge Current × time A s (coulomb, C)
Electric potential or kg m2s−2A−1 (J A−1 s−1
ix. Energy per unit charge
Potential difference or volt V or J C−1)
x. Energy (work or heat) Force × distance travelled kg m2 s−2 (J s−1)
xi. Concentration Mole per cubic metre mol m−3
C = dH/dT kg m2 s−2 K−1 mol−1
xii. Heat capacity p
C = dE/dT (J K−1 mol−1)
v
xiii. Electrochemical equivalent Z = E/F kg C−1 (kg/coulomb)

Note: 1 Litre = 1 dm3

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(cid:190) Some common SI prefixes used for expressing big and small numbers:

Prefix Symbol Magnitude Meaning (multiply by)
Tera− T 1012 1 000 000 000 000
Giga− G 109 1 000 000 000
Mega− M 106 1 000 000
myria− my 104 1 000 0 (this is now obsolete)
kilo− k 103 1 000
hecto− h 102 100
deka− da 10 10
deci− d 10−1 0.1
centi− c 10−2 0.01
milli− m 10−3 0.001
micro− µ 10−6 0.000 001
nano− n 10−9 0.000 000 001
pico− p 10−12 0. 000 000 000 001
femto− f 10−15 0.000 000 000 000 001

1.1 Laws of chemical combination

(cid:190) Chemical combination:
“The process in which the elements combine with each other chemically, to form compounds, is
called as chemical combination.”

(cid:190) Laws of Chemical Combination:
One of the most important aspects of the subject of chemistry is the study of chemical reactions.
These chemical reactions take place according to certain laws called as “Laws of chemical
combination.”
i. Law of conservation of mass:
The law was first stated by Russian scientist Lomonosove in the year 1765. Later in 1774,
French scientist, Antoine Lavoisier also stated the same law independently.
Statement:
It states that, “Mass is neither created nor destroyed during chemical combination of matter.”
Explanation:
a. According to Lavoisier, total masses of the reactants before the reaction are found to be
same as that of total masses of the products formed after the reaction.
b. Eg. AgNO + NaCl ⎯→ AgCl + NaNO
3 3
1.70g 0.555g 1.435g 0.82g
ii. Law of definite composition or constant proportions:
This law was first stated by French chemist Joseph Proust in (1799).
Statement:
It states that, “Any pure compound always contains the same elements in a definite proportion
by weight irrespective of its source or method of preparation.”
Explanation:
a. In support of this law, it was experimentally proved that a naturally occurring pure
sample of copper carbonate contains 51.35 % copper by weight, 38.91 % carbon by
weight and 9.74 % oxygen by weight.
b. Further, a pure sample of copper carbonate was synthesized in laboratory and it was
found that the percentage by weight of copper, carbon and oxygen were exactly identical
to that of the naturally occurring sample of copper carbonate.
c. French scientist Berthollet opposed Proust’s law of definite proportion by giving
examples of the substances containing different proportions of elements.
d. However, Berthollet’s objections were ruled out as the experimental work of analysis
mentioned by Berthollet was found to be based on impure samples or incomplete reactions.

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iii. Law of multiple proportions:
This law was proposed by British scientist John Dalton in 1808.
Statement:
It states that, “If two elements, combine chemically with each other forming two or more
compounds with different compositions by weight, then the masses of the two interacting
elements in the two compounds are in the ratio of small whole numbers.”
Explanation:
a. Hydrogen and oxygen combine to form two compounds H O (water) and H O
2 2 2
(Hydrogen peroxide).
H O : 2 parts of Hydrogen, 16 parts of Oxygen
2
H O : 2 parts of Hydrogen, 32 parts of Oxygen.
2 2
b. The masses of oxygen which combine with same mass of hydrogen in these two
compounds bear a simple ratio 1 : 2.
iv. Law of reciprocal proportions:
This law was given by Richter in 1794.
Statement:
It states that, “When two different elements combine separately with the same weight of a third
element, the ratio in which they do so will be the same or some simple multiple of the ratio in
which they combine with each other.”
Explanation:
a. Definite mass of an element A combines with two other elements B and C to form two
compounds.
b. If B and C also combine to form a compound, their combining masses are in same
proportion or bear a simple ratio to the masses of B and C which combine with a constant
mass of A.
Eg.
H
(A)
NaH HCl

(B) Na Cl (C)

NaCl
Hydrogen combines with sodium and chlorine to form compounds NaH and HCl
respectively.
NaH : 23 parts of sodium, 1 part of Hydrogen
HCl : 35.5 parts of chlorine, 1 part of Hydrogen
Sodium and chlorine also combine to form NaCl in which 23 parts of sodium and 35.5
parts of chlorine are present. These are the same parts which combine with one part of
hydrogen in NaH and HCl respectively.
v. Gay-Lussac’s law of combining volumes of gases:
This law was enunciated by Gay-Lussac in 1808.
Statement:
It states that,“When gases react together to produce gaseous products, the volumes of reactants
and products bear a simple whole number ratio with each other, provided volumes are
measured at same temperature and pressure.”
Explanation:
a. Under similar conditions of temperature and pressure, 1 volume of hydrogen reacts with
1 volume of chlorine to give 2 volumes of hydrogen chloride.
H + Cl ⎯→ 2HCl
2 2
1 volume 1 volume 2 volumes
b. Thus, the volume ratio of hydrogen: chlorine: hydrogen chloride is 1 : 1 : 2.
c. This is a simple whole number ratio and is also in agreement with their molar ratios when
they are involved in the reaction.

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Some Basic Concepts of Chemistry