chemistry notes by atul waghmare government polytechnic autonomus ,aurangabad

8/11/2019 Chemistry Notes by Atul Waghmare Government Polytechnic Autonomus ,Aurangabad

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Prof. Atul Waghmare 9527202189/9657824223

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Chapter I

Atomic Structure

Q. Define Atom

Ans: Atom:Atom is the smallest particle of an element which cannot be

further sub divided and which takes part in all chemical changes.

Q. Define Atomic number &Atomic mass number

Ans: Atomic number(Z):Atomic number is the number of protons present in

the nucleus which is equal to the number of electrons revolving around

the nucleus in extra nuclear part of the atom. OR

The number of protons present in one atom of element is called as atomic

number. It is denoted by the symbol Z.

Z = p = e

The atomic number of Na is 11 & Carbon is 6

Atomic mass number (A):Atomic mass number is the sum of number of

protons & neutrons present in the nucleus of atom of an element

It is denoted by the symbol A

A = p + n

The atomic mass number of Na is 23 & Carbon is 12

Q. Define Isotopes & Isobars with examples

Ans: Isotopes: The different atoms of same element having the same atomic

number but different atomic mass number are called as isotopes

Ex:1H1

, 1H2

, 1H3

. 8O16

,8O17

,8O18


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Isobars: The different atoms of different elements having same atomic

mass number but different atomic numbers are called as isobars.

Ex: 18Ar40

,19K40

, 20Ca40

. 28Ni64

,30Zn64

.

Q. State the properties of isotopes.

Ans: 1) They have same atomic number

2) They occupy same place in periodic table.

3) They have identical electronic configuration

4) They have identical chemical properties

Ex: 1H1,1H2,1H3. 17Cl35,17Cl37,

Q. State the properties of isobars

Ans: 1) They have same atomic mass numbers

2) They occupy different place in periodic table

3) They have different electronic configuration

4) They have different chemical properties

Ex: 92U235

,93Np235

,94Pu235

. 28Ni64

,30Zn64

Q. Why an atom is electrically neutral?

Ans: Atom consists of equal number of positively charged protons in the

nucleus which is exactly balanced by negatively charged electrons

present in extra nuclear part. Therefore atom is electrically neutral.

Q. Why nucleus of an atom is always positively charged?Ans: Atom consists of nuclear part (Nucleus) &extra nuclear part. Nucleus

consists of positively charged protons &charge less neutrons. Therefore

nucleus of an atom is always positively charged.

Q. Why electron do not fall into the nucleus?

Ans: The electrostatic force of attraction between electron & nucleus is exactly

balanced by the centrifugal force so that electron does not fall into the

nucleus.


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Q. Why sodium is electropositive? Explain with electronic configuration.

Ans:

Na (11)1s2,2s

2,2p

6,3s

1

Sodium consist of one valence electron in its outermost shell so it loses

the valence electron & acquires positive charge & becomes

electropositive.

Na Na++ e

-

(2,8,1) (2,8)

Sodium atom sodium ion

Q. State Octet rule with example.

Ans. Statement: The tendency of an atom to have eight electrons in outermost

shell is known as the octet rule.

Ex: Argon[ 18]-(2,8,8) - 1s2,2s

2,2p

6,3s

2,3p

6

Q. State Duplet rule.Ans: Statement: The tendency of an atom with only one orbit to have two

electrons (duplet) in the outermost orbit (shell) is known as duplet rule.

Ex:Helium consist of two electrons in outermost orbit

Q. If 3d &4s orbitalsare available for an electron which orbital will it

occupies first? Why?Ans: It will occupy 4s orbital first because energy of 4s orbital is less than

energy of 3d orbital.

Q. Arrange the following orbitals in the increasing order their

energies2p,4p,3s,3d,4s,3p,2s.

Ans: The increasing order of energies of orbital as per aufbaus principle is as

follows-2s


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Q. State Hunds rule of maximum multiplicity.

Ans: When several orbital of same energy are available then the electrons first

fills all the orbitals with parallel spin before pairing takes place in any

one orbital.

Q. Define valency and valency electrons.

Ans: The valency of an element is the number of electrons that atom can lose,

gain or share so as to complete its octet or duplet and become stable.

Ex: The valency of Na is 1, Mg is 2, Cl is 1 , O is 2

The electrons which are present in outer most orbits (last shell) are

known as valency electrons.

Q. Name isotopes of hydrogen. Draw their atomic diagram.

Ans: The isotopes of hydrogen are Protium, Deuterium and Tritium.

Q. State Aufbau principle.

Ans: Statement: The electrons always enter in the various orbitals in the

order of increasing energy.i.e.the lower energy orbitals are filled first and

then high energy orbitals are filled.

1s


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Q. Write any four postulates or assumptions of Bohrs atomic theory

Ans: Following are the main postulates of Bohrs theory

1.

An atom consist of a dense positively charged central part called as

nucleus, it is at rest.

2.

The electrons revolve around the nucleus in fixed circular path called as

orbit or shell. The electrostatic force of attraction between the nucleus

and electron is exactly balanced by the centrifugal force. So, the electron

does not fall into the nucleus and the atom remains stable.

3.

Out of the number of possible circular orbit around the nucleus, an

electron revolves around the nucleus only in certain permitted orbits

which are known as stationary states.

4. Each stationary state is having definite amount of energy. Therefore,

these are also called as energy shells or energy levels.

5. Electron in the energy level nearest to the nucleus has lower energy and

those are at greater distance from the nucleus have higher energy.

6.

An excited electron can jump from a lower energy level to higher

energy level by absorbing energy. Whereas the excited electron jumps

from higher energy level to lower energy level by emitting (losing) the

energy.


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Q. Differentiate between atomic number and atomic mass number

Ans:

Atomic Number Atomic Mass Number

Atomic number is the number of

protons present in the nucleus is equal

to the number of electrons revolving

around the nucleus in extra nuclear

part of the atom. Z= p= e

It is denoted by symbol Z.

Ex:Atomic no. of Na is 11.

The sum of the number of protons and

neutrons present in the nucleus of an

atom is called as atomic mass number.

A = p + n

It is denoted by symbol A.

Ex: Atomic mass no. of Na is 23.

Different element have different atomic

number. Eg. 2He4, 1H

1, 6C

12

Atoms of same or different elements

may or may not have same atomic mass

number.

Atomic number fixes the position of an

element in the periodic table.

Atomic mass number does not fixes the

position of an element in periodic table

Elements are placed in periodic table

according to their atomic number

Elements are not placed in periodic table

according to their atomic mass number.

Chemical properties of an element

depend on atomic number.

Chemical properties of element are not

depend on atomic mass number

Atomic number does not decide atomic

weight of element

Atomic mass number decide atomic

weight of element


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Q. Compare between proton, electron and neutron with respect to their

symbol, mass, charge and location.ORWrite composition of modern

atom.

Ans: Proton, electron and neutron are the fundamental particles of atom

Description Proton Electron Neutron

Definition It is positively

charged particle

present in the nucleus

of an atom

It is negatively

charged particle

present in extra

nuclear part of an

atom

It is chargeless

(neutral) particle

present in the

nucleus of an

atom.

Symbol It is denoted by the

symbol p+

It is denoted by the

symbol e

It is denoted by the

symbol n

Mass It has mass

1.007825 a.m.u.

It has mass

0.000555 a.m.u.

It has mass

1.008665 a.m.u.

Charge It carries unit positive

charge (+1)

It carries unit

negative charge (-1)

It is chargeless i.e.

( 0) charge

Location Inside the nucleus Extra nuclear part Inside the nucleus


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Q. Differentiate between isotopes and isobars.

Ans:

Isotopes Isobars

They have same atomic number but

different atomic mass number.

They have same atomic mass number

but different atomic number

They occupy same place in periodic

table.

They occupy different place in

periodic table.

They have identical electronic

configuration.

They have different electronic

configuration.

They have identical chemical

properties.

They have different chemical

properties.

They have same number protons and

electrons but different number of

neutrons.

They have different number of

protons, electrons and neutrons.

Ex:1H , 1H , 1H . 8O , 8O , 8O ,

17Cl35

, 17Cl37

. 6C12

, 6C13

, 6C14

,

Ex: 18Ar , 19K , 20Ca . 28Ni,30Zn ,

92U235

, 93NP235

, 94Pu235

.

Q. Differentiate between orbit and orbital.

Ans:

Orbit Orbital ( Atomic orbital )

The electron revolve around the

nucleus in fixed circular path is called

as orbit.

The three dimensional region of space

around the nucleus where probability

(possibility) of finding an electron is

maximum called as orbital.


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They are denoted by capital letters K,

L, M, N etc.

They are denoted by small letters

s,p,d,f. etc.

They have either circular or elliptical

shape.

They have different geometrical shapes

such as s-spherical p-dum bell shape

etc.

The maximum numbers of electrons

in an orbit is given by 2n2

rule i.e.

K=2, L=8, M=18, N=32.

The maximum number of electrons in

any orbital is two with opposite spin

[]

Orbit has two dimensional

representation.

Orbital have three dimensional

representation

The number of orbit from the nucleus

are n=1, 2,3,4,5 etc.

The number of orbital relative to any

orbit is n2=1,4,9,16 etc.

Q. Differentiate between energy level and sub energy level.

Ans:

Energy level Sub-energy level

The electrons revolve around the

nucleus in fixed circular path with

definite amount of energy are known

as energy levels

The close grouping of a number of

energy levels in the main energy level

are known as sub-energy levels.

They are denoted by capital letters

K, L, M, N etc.

They are denoted by small letters s, p,

d, f etc.

They have either circular or elliptical

shape.

The sub energy levels consist of orbital

which have different geometrical shape

such as s- spherical and p-dumbell.


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The maximum number of electrons in

an energy levels is given by 2n2rule,

where, n=main energy number i.e.

K=2, L=8, M=18, N=32

The maximum number of electrons

present in sub-energy levels are s=2

p=6 d=10, f=14.

It describes size of an electron cloud It describes shape of electron cloud.

Q. Differentiate between electrovalent compound and covalent

compound.

Ans:

Electrovalent compound Covalent compound

The compounds which are formed by

loss or gain of electrons between two

dissimilar atoms of an element are

called as electrovalent compound.

The compound which is formed by

mutual sharing of electrons between

two similar or dissimilar atoms of an

element are called as covalent

compound.

They are found to exist in the form of

ions even in solid state.

They are not found to exist in the form

of ions in the solid or liquid state.

They are polar They are non-polar.

They have high melting point and

boiling point

They have low melting point and

boiling point.

They are non-volatile They are volatile.

They are soluble in polar solvent like

H2O and insoluble in non-polar

solvents like benzene CS2, CCl4.

Ex: NaCl, MgO, CaCl2.

They are soluble in non-polar solvent

like benzene, CS2, CCl4, and insoluble

in polar solvent like H2O

Ex: H2, CO2, N2.


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Q. Explain Electrovalency and Covalency with examples.

Ans: Electrovalency:The valency obtained by loss or gain of electrons so as to

complete the octet (or duplet) is called as electrovalency. There are two

types of valency

A) Positive electrovalency

B) Negative electrovalency

A) Positive electrovalency: The valency obtained by loss of valence

electron by metallic atom so as to complete its octet is called as positive

electrovalency. Ex:Sodium atom loses one electron to complete its last

shell. Thus positive electrovalency of sodium atom is +1

Na Na++ e

-

Atom (2,8,1) Ion (2,8)

2. Negative electrovalency: The valency obtained by gain of valence

electron by non-metallic atom so as to complete its octet is called as

negative electrovalency.Ex: Chlorine atom gains one electron tocomplete its last shell. Thus negative electrovalency of chlorine is -1

Cl + e-

Cl-

Atom (2, 8, 7) Ion (2, 8, 8)

Covalency: The number of electrons that an atom of element can share tocomplete the octet is called as covalency. OR

The valency obtained by mutual sharing of electrons between two similar

dissimilar atoms of an element so as to complete its octet is called as

covalency.

Ex:In the formation of chlorine molecule, each atom of chlorine shares

one electron to complete the octet hence, covalency of chlorine is 1.


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Q. Why Chromium &Copper shows anomalous behavior in electronic

configuration?

Ans: The atomic number of chromium is 24.The expected electronic

configuration of chromium is,

Cr (24) - 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d4.

But the observed electronic configuration of chromium is,

Cr (24) - 1s2, 2s

2, 2p

6, 3s

2, 3p

6, 4s

1, 3d

5.

Because one electron from 4s orbital goes to empty 3d orbital of

chromium and has both 4s and 3d orbitals are half filled

The atomic number of copper is 29.The expected electron configuration

of copper is,

Cu (29) - 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d9.

But the observed electronic configuration of copper is,

Cu (29) - 1s2

, 2s2

, 2p6

, 3s2

, 3p6

, 4s1

, 3d10

.Because one electron from 4s orbital goes to empty 3d orbital of copper

and has 4s orbital is half filled and 3d orbital is completely filled.

As half-filled and completely filled orbitals have less energy and

therefore they are more stable.

Q. Write orbital electronic configuration of elements from Hydrogen to

Argon.

Ans: (Note: While writing electronic configuration remember the order of

filling of electron in orbital-1s


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Q. Write electronic configuration of potassium & calcium.

Ans:

Element Atomic No. Electronic configuration

Hydrogen (H) 1 1s1

Helium (He) 2 1s

Lithium (Li) 3 1s2 , 2s1

Beryllium (Be) 4 1s22s

2

Boron (B) 5 1s ,2s,2p

Carbon (C) 6 1s2,2s2, 2p2

Nitrogen (N) 7 1s2, 2s

2, 2p

3

Oxygen (O) 8 1s

,2s , 2p

Fluorine (F) 9 1s2, 2s

2, 2p

5

Neon (Ne) 10 1s , 2s ,2p

Sodium (Na) 11 1s , 2s ,2p ,3s

Magnesium (Mg) 12 1s2, 2s

2,2p

6,3s

2

Aluminium (Al) 13 1s , 2s ,2p,3s ,3p

Silicon (Si) 14 1s , 2s ,2p

,3s ,3p

Phosphorous (P) 15 1s2, 2s

2,2p

6,3s

2,3p

3

Sulphur ( S) 16 1s , 2s ,2p,3s ,3p

Chlorine (Cl) 17 1s , 2s ,2p ,3s ,3p

Argon (Ar) 18 1s2, 2s

2,2p

6,3s

2,3p

6


Potassium (K) 19 1s , 2s ,2p ,3s ,3p , 4s

Calcium (Ca) 20 1s2, 2s2,2p6 ,3s2,3p6, 4s2


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Q. Write electronic configuration of elements from Scandium to Zinc.

Ans:

Q. Write characteristies (Properties) of inert gases

Ans: Characteristics of inert gases

1) They are chemical resistant

2) They have good insuating Property

3) They have good didecfric Property

4) They have lowest boiling Poinl

5) They have low density


Scandium ( Sc) 21 1s2 ,2s2,2p6 ,3s2,3p6 ,4s2,3d1

Titanium (Ti) 22 1s ,2s ,2p ,3s ,3p ,4s ,3d

Vanadium (V) 23 1s2 ,2s2,2p6 ,3s2,3p6 ,4s2,3d3

*Chromium (Cr) 24 1s ,2s ,2p ,3s ,3p ,4s ,3d

Manganese (Mn) 25 1s ,2s ,2p ,3s ,3p ,4s ,3d

Ferrous (Fe) 26 1s2 ,2s2,2p6 ,3s2,3p6 ,4s2,3d6

Cobalt (Co) 27 1s2 ,2s2,2p6 ,3s2,3p6 ,4s2,3d7

Nickel (Ni) 28 1s,2s ,2p

,3s ,3p

,4s ,3d

*Copper (Cu) 29 1s2 ,2s2,2p6 ,3s2,3p6 ,4s1,3d10

Zinc (Zn) 30 1s2 ,2s2,2p6 ,3s2,3p6 ,4s2,3d10


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Q. Write orbital dectronic contiguarction of linert gases (elements)

Q. State maximum no. of electrons & number of sub shells present in K,

L, M, N orbit (shells)

Ans:

Main shells

(Energy level)

Maximum no. of

electrons

No. of sub shells

K 2 1 i.e. s

L 8 2 i.e.s,p

M 18 3 i.e.s,p,d

N 32 4 i.e.s,p,d,f

Element Symbol Atomic

No.

Electronic configuration

Helium He 2 1s

Neon Ne 10 1s2,2s

2,2P

6

Argon Ar 18 1s ,2s ,2P ,3s ,3PKrypton Kr 36 1s ,2s ,2P ,3s ,3P

,3d ,4s ,4p

Xenon Xe 54 1s2,2s

2,2P

6,3s

2,3P

6,3d

10,4s

2,4p

64d

10,5s

2,5p

6

Radon Rn 86 1s2,2s

2,2P

6,3s

2,3P

6,3d

10,4s

2,4p

64d

10,5s

2,5p

6,4f

14,5d

10,6s

2,6p

6


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Q. Name different subenergy level. State maximum number of electrons

and number of atomic orbital present in s, p, d, and f shell.

Ans:

Sub shells

(Sub energy level)

Maximum no. of

electrons

No. of atomic

orbitals

s 2 1

p 6 3

d 10 5

f 14 7

Q. Explain formation of NaCl molecule. Name the type of bonding in it

OR Describe the formation of NaCl molecule. Predict the valency of

Na and Cl atom in NaCl.

Ans: Sodium chloride molecule is formed by combining one atom of sodium

and one atom of chlorine.

1.

The atomic number of sodium is 11. So its electronic configuration is

(2,8,1). The atomic number of chlorine is 17 so its electronic

configuration is (2,8,7).

2.

Sodium atom contains one electron in the last orbit. So it loses one

valence electron and aquires +1 charge and attains a stable

configuration (2,8) as that of Neon(2,8)

3. Chlorine atom contains seven electrons in last orbit. So it takes one

electron from sodium atom and aquires -1 charge and attains a stable

configuration (2,8,8) as that of Argon (2,8,8)


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4.

These two equally and oppositely charged ions (Na+&Cl

-) are

combined together by electrostatic force of attraction to form sodium

chloride (NaCl).

5.

Thus sodium chloride (NaCl) consists of single electrovalentbond.

6.

The valency of Na is +1and Cl is -1

Q. Explain the formation of MgO molecule. Name the type of bonding in

it. OR Describe the formation of MgO molecule. Predict the valency

of Mg and O atom in MgO.

Ans: Magnesium oxide molecule is formed by combining one atom of

magnesium and one atom of oxygen.

1.

The atomic number of Magnesium is 12 so its electronic configuration

is (2,8,2) .The atomic number of oxygen is 8 so its electronic

configuration is (2, 6).2.2.

Magnesium atom contains two electrons in last orbit. So it loses its

two valence electrons and aquires +2 charges and attains stable

configuration (2,8)as that of Neon (2, 8)

3. Oxygen atom contains six electrons in last orbit. So it takes two

electrons from magnesium atom and aquires -2 charges and attains stable

configuration (2,8) as that of Neon (2, 8,)


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4. These two equally and oppositely charged (Mg++

and O--) ions are

combined together by electrostatic force of attraction to form magnesium

oxide molecule (Mgo).

5. Thus magnesium oxide molecule (Mgo) consists of single

electrovalentbond.

6. The valency of Mg is +2and O is -2

Q. Explain the formation of Calcium chloride (CaCl2) molecule. What is

the nature of bonding in it? OR

Describe the formation of CaCl2molecule. Predict the valency of Ca

and Cl atom in CaCl2.

Ans: Calcium chloride molecule (CaCl2) is formed by combining one atom of

calcium and two atoms of chlorine.

1. The atomic number of Calcium is 20 so its electronic configuration is

(2, 8, 8, 2).

The atomic number of chlorine is17 so its electronic configuration is

(2, 8,7).

2. Calcium atom contains twoelectrons in last orbit. So it loses its two

valence electrons and aquires +2 charge and attains a stable

configuration (2,8,8) as that of Argon (2, 8, 8)


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3.

The electrons lost by calcium atom are gained by twochlorine atoms

and each chlorine atom acquires -1 charge and attains a stable

configuration (2,8,8) as that of Argon (2, 8, 8)

4.

These equal and oppositely charged (Ca++ and 2Cl-) ions are

combined together by electrostatic force of attraction to form calcium

chloride molecule (CaCl2)

5. Thus calcium chloride (CaCl2) molecule consists of single

electrovalentbond.

6.

The valency of Ca is +2and Cl is -1

Q. Explain the formation of Water molecule (H2O)

Ans: The water molecule is formed by combining two atoms of hydrogen and

one atom of oxygen.

1. The atomic number of oxygen is 8 so its electronic configuration is

(2, 6). It contains 6 valence electrons. So it is in short of two

electronsto complete the octet.

2.

Each hydrogen atom has electronic configuration (1). So it is in short

of one electronto complete the duplet.


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3.

Therefore, oxygen atom shares two electrons with two hydrogen

atoms to complete the octet & attains stable configuration (2, 8) as that

of Neon (2, 8). Also hydrogen completes its duplet.

4.

There is a seperate single covalent bond between oxygen and two

atoms of hydrogen.

Q. Explain the formation of Carbon dioxide molecule (CO2)

Ans: Carbon dioxide molecule is formed by combining one atom of carbon and

two atoms of oxygen.

1. The atomic number of carbon is 6. So its electronic configuration is

(2,4). It contains 4 valence electrons. So it is in short of four

electronsto complete the octet.

2.

The atomic number of oxygen is 8. Each oxygen atom has electronic

configuration (2, 6).

3. It contains 6 valence electrons. So it is in short of two electrons to

complete the octet.


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4.

Therefore carbon atom shares fourelectrons with two oxygenatoms

to complete the octet and attains stable configuration (2,8)as that of

Neon (2,8).

5.

There is a seperate double covalent bond between carbon and two

oxygen atoms.

Q. Explain the formation Nitrogen molecule.

Ans: The nitrogen molecule is formed by combining one atom of nitrogen with

other atoms of nitrogen. It is a diatomic.

1.

The atomic number of nitrogen is 7. Each nitrogen atom has electronic

configuration (2, 5). It contains 5 valence electrons so it is in short of

three electronsto complete the octet.

2. Therefore, nitrogen atom shares three electrons with other nitrogen to

complete the octet and both attain stable configuration (2,8) as that of

Neon (2,8)


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3.

There is a triple covalent bondbetween two nitrogenatoms.

Q. Explain the formation of chiorine molecule (Cl2).

Ans: In the formation of chlorine molecule one atom of chlorine combines

with other atom of chlorine.

1. The atomic number of chlorine is 17.

2. Each chlorine atom has electronic configuration (2,8,7) i.e. it contains

7 valency electrons. So it is in short of one electron to complete theoctet.

3. Therefore, each chlorine atom share one electronwith other chlorine

to complete the octet and attains stable configuration as that of Argon,

inert gas

4.Thus chlorine molecule (Cl2) constitutes single covalent bond

between two chlorine atoms.


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Q. Explain the formation ethylene molecule.

Ans: The ethylene molecule is formed by the combination of two atoms of

carbon and four atoms of hydrogen.

1) The atomic number of carbon is 6 & hydrogen is 1.

2) Each carbon atom has electronic configuration (2,4) i.e. each contains

4 valency electrons. So they are in short of four electronsto complete

the octet.

3) Each hydrogen atom has electronic configuration (1) i.e. they are in

short of one electronto complete the duplet.

4) The ethylene molecule is formed by sharing two pairs of electronsbetween two carbon atoms and by sharing one electronwith each of

four hydrogen atoms.

5) Thus, two shared pairs form a double covalent bond between two

carbon atoms, four single covalent bondbetween carbon and hydrogen

atoms in ethylene molecule.

Q. Explain the formation acetylene molecule.

Ans: Acetylene molecule consists of two atoms of carbon and two atoms of

hydrogen

1)

The atomic number of carbon is 6 & hydrogen is 1.

2) Each carbon atom has electronic configuration (2,4) .i.e. each contains

4 valency electrons. So they are in short of four electronsto electrons

to complete the octet.


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3) Each hydrogen atom has electronic configuration (1) i.e. they are in

short of one electronto complete the duplet.

4) The acetylene molecule is formed by sharing three pairsof electrons

between two carbon atoms and one pair of electron between carbon andhydrogen atoms.

5) Thus, acetylene molecule is formed by forming triple covalent bond

between two carbon atoms and single covalent bondwith each hydrogen

atom.

Q. Define Element, Molecule

Element: An element is a substance which cannot be break into two or

more simpler. Substances by the chemical methods of applying heat, light

or electric energy. Ex: Hydrogen, Oxygen

Molecule: A molecule in an electrically neutral group of two (or more)

atoms chemically bonded together or A molecule is the smallest particle

of a substance (element or compound) which has the properties of that

substance & can exist in the free state. Ex:Nacl, H2O, N2


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Chapter II

Electrochemistry

Q. Define following terms.

1.

Conductor:A substance which all ows electri c cur rent to pass thr ough

itis called a conductor.

Ex:all metals, impure water, graphite, fused salts, aqueous solution ofacids, bases and salts.

2.

Insulator:It is a substance which does not al low the electri c current to

pass through it.

Ex:wood, paper, rubber, plastics, oils, alcohols, glass, petrol etc.

3. Dielectric: The materials which are used to prevent the loss of

electri city thr ough certain parts in an electri cal systemare known as

dielectrics or electrical insulating materials.

4.

Electrolyte:These are the substances which in aqueous solution or in

molten (or fused) state l iberate ionsand all ow electri c current to pass

through i tresulting in its chemical decomposition.

Ex: Acids, bases and electrovalent salts.


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5. Electrolysis: It is the process of chemical decomposition of an

electrolyte by passage of electric currents.

6.

Strong electrolyte: Electrolytes which are highly ioni zed in solution

and hence have a high degree of ionization known as strong

electrolytes.

Ex: Strong acids like H2SO4, HCl , HNO3,Strong bases like KOH,

NaOH and electrovalent salt NaCl, KCl etc.

7.

Weak electrolyte:Electrolytes which are weakly ionizedin the solution

and hence, have a low degree of i onizationknown as weak electrolytes.

Ex:organic acids like acetic acid, oxalic acid, weak bases like NH4OH

and salts like BaSO4,Al(OH)3etc.

8. Non-electrolyte: It is a substance which is non-conductor of

electricity. Ex:alcohol, petrol, oils, starch, sugar are non electrolytes.

Q. Define metallic conductor and electrolytic conductor.

Ans: Metallic conductor:These are the substances which conduct electricity

without any chemical decomposition

Ex:All metals,graphite etc.

Electrolytic conductors: These are the substance which in aqueous

solution or in molten (or fused) state liberates ions and allows electric

current to pass through it, resulting in its chemical decomposition.

Ex:Acids, bases and electrovalent salts.


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Q. Define cathode and anode.

Ans: Cathode: The electrode which is connected to the negative pole (or

terminal) of the battery is called cathode or negative electrode . When an

electric current is passing there is a flow of electrons from negative pole

of battery to the cathode.

Anode:The electrode which is connected to the positive pole(terminal)

of the battery is called anode or positive electrode. When an electric

current is passing there is a flow of electrons from the anode to the

positive pole of battery.

Q. Why blue colour of copper sulphate solution turns to colourless after

its electrolysis by using platinum electrode?

Ans: When a current is passed through a CuSO4solution by using platinum

electrodes then Cu++

ions (blue) discharged at cathode hence afterelectrolysis CuSO4solution turn to the colourless at cathode.

Cu++

+2e-Cu

Q. Justify the following. Instead of H+ ions only Cu

2+ ions migrate

towards cathode in the electrolysis of CuSO4Solution.Ans: Discharged of cations at cathode depends on position in the activity

series of cations.

i.e.Cation at lower position is discharged easily than cation at higher

position.

Ex:In case of electrolysis of CuSO4solution there are H+& Cu

2+ions but

only Cu2+ions migrate towards cathode as they are at lower position than

H+ions in activity series.


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Q. Why copper is electrorefined when it is to be used in electrical

industries?OR Why blister copper is electro refined?

Ans: Blister copper contains 3 to 5% impurities like Zn,S,As,Ni,Au etc. Such

impure copper is not fit to be used as an electrical conductor.

Conductivity is lowered by the traces of impurities. Copper with 100%

purity is required for electrical conductivity. Hence the blister copper is

refined by the process of electro refining.

Q. Define ionization.

Ans: The process of breaking of substance into charged atoms, radicals or

ions is known as ionization. i.e. ionization is process of formation of

ionsin solution or in fused state or gaseous state.

Ex. Heat causes ionization of gas.

Q. Define electrolytic cell and electrochemical cell.

Ans: Electrolytic cell:

It is the device in which electri cal energy is converted into chemical

energy.

Due to passage of electric current non spontaneous chemical reaction take

place.

Electrochemical cell:

It is the device in which chemical energy is converted into electri cal

energy.

In this type of cell the electricity can be generatedby spontaneous redox

reaction.


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Q. Differentiate between following

Ans:

1.

Strong electrolyte and Weak electrolyte

Strong electrolyte Weak electrolyte

Electrolytes which are highly ionised

in solution hence having high degree

of ionisation are known as strong

electrolyte.

Eg: Strong acids like HCl,H2SO4,

strong bases like NaCl, KOH etc.

Electrolytes which are feebly (weakly)

ionised in solution hence having low

degree of ionisation are known as weak

electrolyte.

Eg:Weak acid like CH3COOH,

H2CO3,weak bases like NH4OH

2.

Metallic conduction and Electrolytic conduction

Metallic conduction Electrolytic conduction

It involves flow of electrons in a

conductor

It involves movement of ions in a

solution

There is no change in the chemical

properties of conductor.

The chemical reactions take place at the

electrodes with the decomposition of

the electrolyte.

It does not involves any transfer of

matter

It involves transfer of electrolyte in the

form of ions.

It shows the increase in resistance as

the temperature is increased

It shows the decrease in resistance as

the temperature is increased


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Q. Define PH

and POH

.

Ans: PH: P

Hof a solution can be defined as the negative logarithm to the

base 10 of hydrogen ion concentration expressed in mole/ litre

PH= -log10 [H

+]

POH

: POH

of solution can be defined as the negative logarithm to the

base 10 of hydroxyl ion concentration expressed in moles/litre.

POH

= -log10[OH-]

Q. What is PHScale? State its significance.

Ans: Hydrogen ion concentration in molarity is conveniently expressed on

logarithmic scale known as PHScale.

It is a simple logarithmic scale. It is the measure of acidity, alkalinity and

neutrality of solution. It is numerically expressed from 0 to 14.

Significance:

1) When PHvalue of a solution is 7, then solution is neutral.

2) When PHof a solution is less than 7, then solution is acidic.

3) When PH

of a solution is greater than 7, then solution is basic

4) When PH=14 then solution is extremely basic.

5) When PH=0 then solution is extremely acidic.


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Q. What is the PH of extremely acidic and basic solution?

Ans: For extremely acidic solution PHis Zero (0)

For extremely basic solution PH

is fourteen (14)

Q. Define electrolytic dissociation.

Ans: The process of breaking up of an electrovalent compound

(electrolyte) into ions when dissolved in solvent like water is called as

electrolytic dissociation.

Q. Explain Arrhenius theory of Dissociation. ORState four postulates of

Arrhenius theory of ionization. OR Write the four assumptions of

Arrhenius theory of ionization.

Ans: In 1887 Arrhenius put forward theory of ionization. The main postulates

of Arrhenius theory are as follows.

1. When a molecule of electrolyte is dissolved in solvent like water, it

produces

Positively charged cation

Negatively charged anion

2.Cations are obtained from metal by the loss of electrons

Na Na++ e

-

(2,8,1) (2,8)

Atom Cation (Sodium ion)

Anions are obtained from non metal by the gain of electrons

Cl + e- Cl

-

(2, 8, 1) (2, 8, 8)

Atom Anion (Chloride ion)


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3. In a solution total number of positive charges on cations and total

numbers of negative charges on anions are equal and hence solution as a

whole electrically neutral.

CaCl2 Ca++ + 2Cl

4. The number of positive charges on cation and negative charges on

anion indicates the valency of that element from which it is derived

BaCl2 B a++ + 2Cl

5. Cation and anions present in solution are constantly reuniting to form

original undissociated molecule

NaOH N a++ OH

Q. Define degree of ionization. Explain the factors affecting degree of

ionization.

Ans: Degree of ionization: The fr action of the total numbers of molecules of

an electrolyte that ionizesin solution is known as degree of ionization.

Degree of ionization = Numbers of molecules ionised into ions

Total number of molecules dissolved in solvent

Following are the factor affecting degree of ionization

1)Nature of solute

2)

Nature of solvent

3)

Concentration of solution

4)

Temperature

Nature of solute:


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Ionic compounds like acids, bases and salts are highly ionized in solution.

Strong electrolyte like HCl, H2SO4, NaOH, NaCl are highly ionised but

weak electrolyte like CH3COOH,NH4OH etc are weakly ionised. Hence

degree of ionization depends upon the nature of solute.

Nature of solvent:

In polar solvent like H2O, NH3degree of ionization is more. In non polar

solvents degree of ionization is less i.e. degree of ionization depends on

the nature of solvent.

Concentration of solution:

The degree of ionization is inversely proportion to the concentration of

solution. If concentration of solution is more, then degree of ionization is

lessEx:8 Molar HCl ionizes to only 80% while 0.1molar ionizes to 100%

Temperature: At higher temperature molecules aquire higher thermal

energy hence degree of ionisation increases with increases in temperature.

Q. Define electrode potential. What is oxidation &reduction potential?

Ans: Electrode Potential: It is defined as the difference of potential between

the electrode and its sur rounding solu tionat equilibrium.

Oxidation Potential:It is defined as the difference of potential between

the electrode and its surrounding solution at equilibrium due to

oxidation. Ex:Zn electrode dipped in its salt (ZnSO4) solution.

Reduction Potential:It is defined as the difference of potential between

the electrode and its surrounding solution at equilibrium due to

reduction Eg: Cu electrode dipped in its salt solution (CuSO4) solution


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Q. Explain mechanism of electrolysis with suitable example.

Ans: Electrolysis:It is the process of chemical decomposition of an electrolyte

by passage of electric currents.

Consider, electrolysis of fused electrolyte AB (salt) taken in electrolytic

cell. Two electrodes are dipped in it. Cathode is connected to the negative

terminal and anode to the positive terminal of the battery.

The salt is ionised as,

AB A+ + B-

Salt Cation anion

When electric current is passed through the bath, electrolysis take place

At Cathode: Cations (A+

) move towards cathode and get discharged by

attracting electrons and become neutral atom.

A+ + 1e- A (Reduction)

This is primary reaction at cathode.

At anode: Anions (B-) move towards anode and get discharged by losing

electrons and become neutral atomB- B + 1e- (Oxidation)


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This is primary reaction at anode. If the product of primary reaction is

not stable then secondary reaction takes place ,to form stable product.

Examples:

At cathode:Reduction of cation takes place

Na++ 1e

- Na(neutral sodium atom)

At anode: Oxidation of anion take place

Cl- Cl + e

-(neutral chlorine atom)

Q. Explain the electrolysis of CuSO4 solution using platinum electrode.

Write the product of electrolysis.

Ans: Aqueous solution of CuSO4 contains H+, Cu

++, OH

-and SO4

--ions

According to electrochemical series, Cu++

ions are discharged at the

cathode in preference to H+ ions and copper is deposited as cathode. At

anode,OH-ions are discharged in preference to SO4

--ions and oxygen is

liberated at anode

Then ionization of CuSO4takes place which is shown below

CuSO4 Cu+++ SO4- - (strongly ionised)

H2O H++ OH

- (weakly ionised)

At cathode: (Reduction)

Cu++

+ 2e- Cu (s)

Ion Neutral atom


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At anode : ( Oxidation)

2OH- H2O + O2+ 2e

-(Primary reaction)

Neutral radical

A neutral radical (OH) is not stable product, hence secondary reaction

take place.

4OH 2H2O + O2(Secondary reaction)

Product of electrolysis:

1. At cathode, Cu is deposited and at anode O2gas is evolved (liberated)

2.

In electrolytic cell, colourless sulphuric acid is formed

(2H++ SO4

- - H2SO4)

Q. Explain electrolysis of CuSO4 solution using copper electrode. Write

the product of electrolysis.

Ans: Aqueous solution of CuSO4 contains H+, Cu

++, OH

-and SO4

--ions

According to electrochemical series, Cu++ ions are discharged at the

cathode in preference to H+ions and copper is deposited as cathode.

At anode,Cu++ions are formed as when a same metal in contact with its

own salt solution. These Cu++

ions go to cathode and discharged.

Then ionization of CuSO4takes place which is shown below.

CuSO4 Cu++

+ SO4- -

(strongly ionised)

H2O H+

+ OH-

(weakly ionised)


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At Cathode: (Reduction)

Cu++

+ 2e- Cu(s)

At Anode: (Oxidation)

Cu(s) Cu++

+ 2e-

Product of electrolysis:

1. Cu metal is deposited at cathode

2.

Cu anode is slowly dissolved in solution

3.

Neither SO4- -

nor OH-

ions are dischargedTherefore concentration of CuSO4solution remains constant

Applications:

1.

This process is useful for refining (purification) of copper.

2.

It is also used in copper plating.

Q. State Faraday`s first law of electrolysis.

Ans: Statement: The weight of substance deposited or liberated at an

electrode during electrolysis is directly proportional to the quanti ty of

electr icity passedthrough its solution.

Explanation: If W is the amount of substance depositedor liberated at

an electrode and Q is the quantity of electricity passed through the

electrolyte solution

Then, W Q

But C = Q/t

Q = ct

W ct

W = Z c t

Where, c = Current in ampere


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t= time in seconds

Z= Electrochemical equivalent.

If c =1 ampere and t = 1 sec

Then W= Z

Q. State & explain faradays second law of electrolysis. Give its

mathematical relation.

Ans: Statement: When same quanti ty of electri cityis passed through different

electrolyte arr anged in series then the weight of different substances

deposited or l iberatedat the respective electrode is directly proportional

to the chemical equivalents(Equivalent weight of substance)

Explanation: Let the same electric current is passed through CuSO4and

AgNO3solution arranged in series as shown in figure.

According faradays 2nd

law

Weight of copper (Cu) deposited (Wcu) Chemical equivalent of

copper (Ecu) - - - - - - - - - - - - - (1)


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Weight of silver (Ag) deposited (WAg) Chemical equivalent of

Silver (EAg) - - - - - - - - - - - - - (2)

Dividing equation (1) by (2) we get

Weight of Cu deposited (Wcu) = Chemicl aequivalent of Cu (Ecu)

Weight of Ag deposited (WAg) Chemical equivalent of Ag (EAg)

Wcu = Ecu OR W1 = E1

WAg EAg W2 E2

Q. Define electrochemical equivalent. State the relation between

chemical equivalent (CE) and electrochemical equivalent (ECE).

Ans: Electrochemical equivalent of a substance is defined as the weight of

substance deposited or liberated at an electrode when a current of 1

ampere passed for 1 secthrough its solution.

Equivalent weight of substance (C.E.) is 96,500 times the electrochemical

equivalent. Therefore,

Chemical equivalent (C.E.) = 96,500 Electrochemical equivalent

C. E. = 96,500 E.C.E.

Q. Define electroplating. Describe electroplating of silver with diagram.

Ans: Electroplating: It is the process of obtaining metall ic coating of a

superi or metal (li ke si lver , gold, nickel, Cr) on infer ior base metalwith

the help of electr ic cur rentis called as electroplating.


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The purposes of electroplating are as follow,

1.

For decoration purpose

2.

Protection from corrosion

3. Repairing of worn out machinery parts

4. To improve surface hardness of metals

5.

For making plastic surface conducting

Principle:An active coating metal as anode deposits on cathodic articlein the electrolytic cell with the help of electric current. Ex:Electroplating

of silver on iron spoon.

Process:

A plating of silver on iron spoonis done in a rectangular tank made up of

steel. Potassium argentocyanide solution K [Ag (CN) 2] is used as

electrolyte.

1.

The iron spoon is first thoroughly cleaned by boiling with caustic soda to

remove grease and dirt.


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2.

Then it is washed with water until free from caustic soda. Then it is

treated with dil. HCl to remove any oxide layer. Again it is washed with

water and polished carefully.

3.

The iron spoon is then made as cathode. The plate or block of pure silver

metal is made as anode.

4.

The cathode and anode both are immersed in electrolytic solution taken in

cell.

5.

When current is passed, then iron spoon get plated with a smooth and

bright deposit of silver.

6.

The silver anode gets slowly dissolved in solution by giving Ag+ ions

Ionisation of K [Ag (CN) 2] take place as follows

K [Ag (CN) 2]- K

++ [Ag (CN) 2]

-

[Ag (CN) 2]- Ag

++ 2CN

-

At cathode-Ag++ e- Ag

At anode- Ag Ag++ e-

Q. What is electrorefining? Explain electrorefining of blister copper

(impure copper) with diagram.

Ans: Electrorefining: Electrorefining is the process in which pure metal can

be obtained from impure metalby the method of electrolysis.

Principle: An impure metal as anode dissolves and gets deposited at

cathode by passing the electric current

.Example: Electrorefining of blister copper


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Process: In this process15% CuSO4+ 5-10%H2SO4solution is used as

electrolyte

The thick rod of impure copperis made as anode

A thin strip of pure copperis made as cathode.

1.

The two electrodes are then dipped in an electrolytic cell containing

CuSO4solution

2.

On passing electric current Cu anode is slowly dissolved in solution

and deposited on the surface of cathode

3.

The impurities of less active metal like Ag, Au and Pt fall down from

the anode and settle below anode as anode mud.

4. From anode mud, precious metals like Ag, Au and Pt are recovered.

Electro refined copper is 99.95% pure

Ionisation:CuSO4 Cu+++ SO4

- -

H2O H++ OH-

At cathode - Cu++

+ 2e- Cu(s)

At anode - Cu(s) Cu+++ 2e-


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Q. Define following terms

Ans: 1) Cell:

A cell is a device in which either electrical energy is converted to

chemical energy or chemical energy is converted to into electrical

energy.

2) Battery:

Battery is a device in which many cellsare connected in series.

3) Charge (Charging):

This is the operation of a cell when an external source of current

reverses the electrochemical reaction of the cell to restore the battery to

its original state.

4) Discharge (Discharging):

This is the operation of a cell when current flows spontaneously fromthe battery into the external circuit.

Q. Define electrolytic cell and electrochemical cell.

Ans: Electrolytic cell:

It is the device in which electrical energy is converted into chemical

energy. These cells are also known as voltameters. Due to passage ofelectric current non spontaneous chemical reaction take place.

Electrochemical cell:

It is the device in which chemical energy is converted into electrical

energy. In this type of cell the electricity can be generated by

spontaneous redox reaction.


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Q. Give the classification of batteries.

OR How batteries are classified?

Ans: Batteries are classified into

1. Primary battery:

The type of battery in which cell reaction is not reversible is called

as primary battery.

These are not rechargeable. If these are discharged then discarded.

e.g.Dry cell, Daniel cell

2. Secondary battery:

The type of battery in which cell reaction is reversible is called as

secondary battery.

These are rechargeable.

e.g.Lead acid storage cell, Ni- Cd-cell.

3.

Reserve battery:

It is a battery in which active material are kept separated by special

arrangements.

Such a battery is designed for long storage before use.

e.g. Gordon-magnesium battery, Silver chloride cell.


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Q. Differentiate between Primary cell and Secondary cell OR How

electrochemical cells are classified?

Ans: Electrochemical cells are classified into primary cell and secondary cell

Primary Cell Secondary Cell

The type of cell in which net cell

reactions cannot be reversed on

applying higher e.m.f. is called as

primary cell

The type of cell in which net cell

reactions can be reversed on applying

higher e.m.f. is called as secondary

cell

Its cost is low Its cost is high

It is light in weight It is heavier

Itslife is short Its life is longer

It cannot recharge once discharged

E.g. Dry cell, Daniel cell.

It can be recharged number of times.

E.g. Lead acid storage cell, Ni- Cd cell

Q. State Ohms law with mathematical equation and meaning of each

symbol used in it

Ans: Statement:

The strength of current flowing through a conductor is directly

proportional to the potential difference applied across the conductor and

inversely proportional to the resistance of the conductor.

i.e. I = E / R

Where, I = current

E = potential difference

R = Resistance


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Q. Define Specific conductivity and equivalent conductivity. State their

units. State the relation between equivalent conductivity and specific

conductivity

Ans: Specific conductivity (conductance) is the reciprocal of specific

resistance. OR It is also defined as the conductance of 1cm cube of

solution

It is denoted by (K) kappa.

The unit is ohm-1

cm-1

Equivalent conductivity (conductance) is defined as the conductivity of a

solution containing 1gm equivalent of the electrolyte

It is denoted by

The unit is ohm-1

cm2eqvt

-1

= KV

Where, V is volume of solution containing 1gm equivalent of an

electrolyte.

But V = 100/ CWhere, Cis concentration in gram equivalent/ litre

= K 1000

C

This is the relation between equivalent conductivity and specific

conductivity


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Q. Explain the construction and working of Dry (Leclanche) cell. Give

two applications of Dry cell. OR Describe construction and working

of ZnMnO2cell

Ans: Dry cell is modified form a leclanche cell. It is primary cell. It is

irreversible and cannot be recharged.

Construction: Dry cell consist of

1. Zn vesselwhich acts as anode

2.

A graphite rod surrounding by a paste made up of graphite powder,

manganese dioxide (MnO2) and waterplaced in muslin cloth, It acts asacathode.

3. A paste of ammonium chloride (NH4Cl), Zinc chloride (ZnCl2) and

water

Working: The following electrode reactions takes place.

At anode:

Zinc dissolves in solution to form zinc ions

Zn Zn++

+ 2e-(oxidation)

Zn++ions produced combine with NH3to form its complex

Zn++

+ 4NH3 Zn (NH3)4++


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At cathode:

The ammonium ion reacts with MnO2to liberate ammonia (NH3)

2NH4+ + 2MnO2 + 2e

- Mn2O3 + H2O + 2NH3

The voltage of cell is 1.5 volt.

The cell cannot be recharged because it is not possible to reverse the cell

reaction

Applications:

It is used in calculator, radio, watches, tape recorder, flash light andtransistor.

.

Q. Explain construction and working of Lead acid storage cell (Lead

accumulator). Write charging and discharging reactions.

Ans: It is secondary cell it is reversible cell and can be charged.

Construction:

1. Lead acid storage cell consist of lead platewhich acts as anodeand

lead plate coated withlead oxide (PbO2)which acts ascathode.

2.

Several such an anode and cathode pairs are connected in parallel and

are dipped in 20% of H2SO4solution with specific gravity 1.25g/cm3.

3.

The battery is encased in plastic or glass container.

4.

Each pairs of anode and cathode produces a voltage of 2Volt.


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Working:

Due to the formation of waterin the cell the acid get diluted. When its

specific gravityfalls below 1.25gm/cm3the battery needs charging.

The following discharging and charging reactions take place.

Discharging

At anode: Pb + SO4--

PbSO4+ 2e-

Charging

Discharging

At cathode: PbO2+ SO4-- + 4H++2e- PbSO4+ 2H2OCharging

_________________________________________________________

Net cell reaction:

Discharging

Pb +PbO2+ 4H++2SO4

-- 2PbSO4+ 2H2O

Charging

During charging lead & lead oxide is again deposited on anode & cathode

respectively & charging reaction is

Discharging

2PbSO4 + 2H2O Pb + PbO2+ 2H2SO4Charging

Applications:

1.

Lead acid battery used in starting motor

2.

It is used in UPS system & research centers

3. It is used in marketing area, railway signaling in mines, laboratories

and hospitals

4.

It is used in security alarms system


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Chapter III

Metallurgy

Q. Define Following Terms.

Mineral:A naturall y occurr ingsubstance present in earth crustwhich

contains metal in free state or in combined stateis known as mineral.

Ex: Hematite (Fe2O3) , Galena (PbS), Limestone (CaCO3) .

Ore: A mineral from which a metal can be extracted economically &

easily is called as ore.

Ex: Hematite (Fe2O3) is ore of iron, Bauxite (Al2O3.H2O) is ore of

aluminium

Gangue Or Matrix:The unwanted impur ities l ike sand, clay ,rocksetc.

associated with the ores are called as gangue or matrix.

Ex: In Hematite (Fe2O3) ore, silica is gangue.

Flux:The substance used during extraction of metalto remove gangue

isknown as flux.

Ex: For removal of gangue like silica (SiO2), calcium oxide (CaO) is

used as flux

Slag: The fusible substance formed by combination of added fl ux &

ganguepresent in ore is known as slag.

SiO2 + CaO


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Metallurgy: Metallurgy is the process of extraction of metal easily,

economically and profitably from their ores.

Ex: Iron is extracted from Hematite ore.

Q. Define following terms.

1. Hardness:It is the ability of the metal to resist wear or abrasion &

resist penetration.

Ex: Tungsten metal is found to be the hardest metal

2. Ductility:It is the property of the metal by which it can be stretched

into lengthand allows it to drawn into wireswithout breaking.

Ex: gold, silver, and platinum having this property can be easily

drawn into wires.

3.

Malleability:It is the property of metal by which it can berolled into

thi n sheet without breaking.

Ex: Gold, silver, platinum, copper, aluminium, are most malleable

metals.

4.

Toughness: The property of a metal to resist repeated shocks or

vibrationswithout breaking is called as toughness

Ex:Gold & Silver are tough metals.

5. Tensile Strength: The tensile strength of a metal is the ability of

metal to carry loadwithout breaking.


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6. Brittleness: It is the property of a material (like glass) which dont

permit permanent deformation without breakage.

7.Weldability: It is the process of uniting two pieces of metals by

means of heat by bringing their ends in the molten state.

8. Castability:(Casting):It is the process of pouring molten metalinto

a mould& allowing it to solidify is known as casting.

9.

Machinability:A property due to which a metal can beeasily cut by

cutting tools to produce a desired shape & surface finish on its

surface.Ex: Sawing, Shaping, Drilling, etc.

10.Forging:It is the process of giving predetermined shapeto a piece of

metal at sufficiently high temperature when metal is in the plastic state

it is known as forging.

11.Soldering: It is defined as a process of joining the metal surface by

introducing a molten non ferrous alloy with melting point below

4000

Cbetween them is known as soldering.

12.Brazing: It is defined as a process of joining the metal surface by

introducing a molten non ferrous alloy with melting point above

4000Cbetween them is known as brazing.


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Q. Define concentration of ore. Name physical & chemical processes of

concentration of ore.

Ans: The process of removal of unwanted (Gangue or matrix) impurities from

the ore is called as concentration of ore.

Physical Process (Methods)

1) Gravity separation method

2)

Magnetic separation method

3) Froth floatation method

Chemical Process (Methods)

1.

Calcination

2.

Roasting

Q. Why wood metal is used in electric fuse?

Ans: The melting point of wood metal is 710C.So it is easily fusible. As the

fuse wire is made up of wood metal due to sudden high voltage the

temperature of the fuse wire increases and wire gets melted and the

circuit breaks. This makes the current supply off, which keeps the

electrical equipment safe and saves from damage.

Q. Define refining. Name the methods of refining of metals.

Ans: The process of purification a metal to get extra pure metal is called as

refining.

The methods used for refining of metals are as follows.

1. Poling

2.

Liquation

3.

Distillation

4. Electrolytic refining


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Q. Define alloy and binary alloy with example.

Ans: Alloy:The homogeneous mixture of two or more element in which one

must be a metal.Ex: Brass, Bronze.

Binary alloy:The alloy which contain only two components is known as

binary alloy Ex:Brass (Cu+Zn), Bronze (Cu+Sn)

Q. When alloy is called amalgam? Give two examples. OR What is

amalgam.

Ans: An amalgam is prepared by mixing element with mercury.

When an alloy contains mercury as one of the component then it is called

as amalgam.

Ex: Na- Hg Zn- Hg

Q. Name the methods of preparation of alloys.

Ans: Following are the methods used for preparation of alloy.

1. Fusion

2.

Compression

3.

Electrode position 4.Reduction

Q. Give classification of alloys based on its composition.

Ans: Alloys are classified into two types

1)

Ferrous alloys

2)

Non-Ferrous alloys

Ferrous alloys:These alloys have iron as one of the main component

Ex: Magnetic steel, Stainless steel etc.


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Non- ferrous alloy:These alloys do not contain iron as one of the main

component. Ex: Brass, Bronze, Duralumin etc.

Q. State the purposes of alloying of metals

Ans: 1) To increase the hardness of a metal

2) To increase the tensile strength

3) To increase corrosion resistance of metal.

4) To modify colour.

5) To change the chemical reactivity.

6) To lower the melting point of metal.

7) To reduce malleability & ductility.

Q. State the ingradients added to blast furnace for extraction of iron.

Ans: Haematite ore (Fe2O3) Coke (c) and Limestone (CaCO3) are the

ingradient in the proportion 8:4:1added to blast furnace for extraction of

iron.

Q. Name the products of blast furnace. Give one application of each.

Ans: The products of blast furnace are pig iron, slag and flue gases.

Applications:

i) Pig iron: It is used for stoves, lamp posts, drainage covers, pipes,

railing etc

ii) Slag: It is used for road building, cement manufacturing and as

fertilizers

iii) Flue gases: Used as fuel

Q. Explain with justification coke and limestone are added during the

extraction of iron. OR What is function of coke and limestone in

extraction of iron by the blast furnace


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Ans: During the extraction of iron from its ore smelting is done in blast

furnace. During the process of smelting coke is added as reducing agent

and limestone as flux to remove impurities. Coke reduces haematite ore

to metallic iron. Lime stone (CaCO3) decomposes to lime which

combines with impurities of silica to form calcium siliate which is

removed as slag.

Q. What are the different zones of blast furnace according to temperature.

Ans: Blast furnace is divided into three temperature zones

i)

Zone of reduction3000C to to 800

0C-

ii)

Zone of heat absorption- 8000

C to 12000

Ciii) Zone of fusion1200

0C to 1500

0C

Q. Write the chemical reactions taking place in the zone of reduction.

Ans: Following reactions take place in the temperature range 3000-800

0C i.e. Zone

of reduction.

1.

At the top of the furnace the charge is heated between 300 0C to 5000C, Fe2O3

is converted into Fe2O4

3Fe2O3+ CO 2Fe3O4+ CO2 .Ferric oxide Ferroso ferric oxide (stable upto 6500C)

2.

At temperature between 6500C- 7000C, Fe3O4 is converted into FeO

Fe3O4+ CO 3FeO + CO2

3.

At temperature between 7000C- 8000C, FeO is converted to metallic iron

FeO + CO Fe + CO2

4.

At the same temperature 3000C8000C, limestone is decomposed to lime.

CaCO3 CaO + CO2


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Q. Write the chemical reactions takes place in the zone of heat absorption.

Ans: Zone of heat absorption has temperature range 800-12000C. In this

temperature zone following reactions takes place.

1. Any oxide of iron which is not reduced in the zone of reduction is reduced

by red hot carbon and also carbon dioxide is reduced by red hot carbon to

carbon monoxide by the absorption of heat.

Fe2O3+ 3C 2Fe + 3CO + heat

CO2 + C 2CO + 39 Kcal

2. The hot iron meets the carbonmonoxide to carbon which is absorbed by

hot iron.

2CO CO2 + C

3.

The lime obtained in the zone of reduction by decomposition of lime stonecombines with silica and forms calcium silicate i.e. slag.

CaO + SiO2 CaSiO3

4. At about 12000C ,non metallic and metallic oxide are reduced by coke to

respective elements

SO2+ 2C S + 2CO

P2O5+ 5C 2P + 5CO

MnO2+ 2C Mn + 2CO

SiO2+ 2C Si + 2CO


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Process:In this process

1. The finely powdered ore is placed on a sloping platform.

2. Then the powdered ore is allowed to flow with water on a sloping

platform.

3.

The platform has depressions on certain intervals.

4. After that the heavier particles of ore settle down (collected) in the

bottom of sloping platform.

5.

The lighter particles of the gangue are washed away with water

Q. Explain electromagnetic separation process with suitable diagram.

OR Name & explain the process used for the concentration of

tinstone ore which contain tungstates of iron & manganese.Ans: This method used for concentration of iron ores, tin ores, tin stone ores.

Principle: This method is based on the principle of magnetism i.e. for

separation of magnetic impurities from non-magnetic particles & vice

versa.

Ex:Tinstone (ore of tin) in which tinstone (SnO2) is non magnetic, while

the impurities like tungastate of iron & manganese are magnetic.


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Process:

1.

In this process firstly the finely powdered ore (containing magnetic

impurities) is allowed to fall through hopper on a non magnetic belt of

leather or rubber moving over the electromagnetic rollers.

2.

Then the magnetic impurities fall below the magnetic roller due to

attraction by magnet.

3. While the non magnetic ore falls in a separate heap away from the

magnet.

Q. Explain froth floatation process with diagram. ORWhich method is

used to concentrate sulphide ore? Explain with diagram.OR Name

the physical method used for concentration of sulphide ore. Explain

it with diagram.

Ans: The froth floatation method is especially used for concentration of

Sulphide ores like copper pyrite (CuFeS2), & Zinc blende (ZnS) etc.

Principle: This process is based on the difference in wetting

characteristics of the gangue particles with oil & water respectively.


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Process:

1.

In this process firstly the powdered sulphide ore is mixed with water

& pine oil.

2. Then the whole mixture of ore, water and pine oil is stirred

vigorously by passing compressed air through it.

3.

After that the oil forms froth with air bubbles.

4. Then sulphide ore particles get attached with the froth & floats on the

surface.

5.

The gangues (impurities) are wetted by water & sink to the bottom of

the tank.

6. The floating froth overflows the tank & collected in the settling basin

where ore particles settle down after some time.

Q. Define smelting. State the principle of smelting of hematite ore using

a chemical equation. OR Coke and limestone is added during the

extraction of iron. Explain with proper justification. OR Describe

smelting process in blast furnace.

Ans: Smelting:It is the process of conversion of oxide into metal.

Principle:It is the reaction of metal oxide with carbon (or its compounds

like Co, CO2, charcoal, coke) at high temperature.


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Process:The calcined or roasted ore is mixed with coke and flux (in the

ratio of 8:4: 1) and heated in a blast furnace or reveberatory furnace, in

the presence of controlled air supply. The reducing agent coke converts

oxide of metal (ore) into molten metal while the flux removes the gangue

in the form of fusible mass known as slag. This process is called smelting

The iron oxide ore, Hematite (Fe2O3) is reduced by using coke as a

reducing agent in the blast furnace.

HeatFe2O3 + 3C 2Fe + 3CO

Hematite Coke Iron Carbon

(Ore) (Reducing agent) metal monoxide

Lime stone i.e. flux removes the impurities in the form of fusible mass

called as slag.

CaO + SiO2 CaSiO3

Flux Gangue Slag

Q. Explain all ores are minerals but all minerals are not ores.

OR Explain the term mineral and ore.

Ans: Ore:A mineral from which the metal can be extracted economically is

called as ore.

Mineral: A naturally occurring substance present in the earth crust

which contain metal in free state or in combined state is called as

mineral.


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It is not possible to extract metal in profitable amount from all the

minerals of same metal.

Ex: Clay & Bauxite are minerals of aluminium but aluminium is

extracted economically from bauxite & not economically from clay

hence, clay & Bauxite are minerals but ore is only Bauxite.

Therefore, all ores are minerals but all minerals are not ores.

Q. Explain the purposes of alloying of metal. OR Write any four

purposes of alloying of metals with suitable examples.

Ans: Following are the main purposes for making alloys.

1. To increase the hardness of a metal:Generally pure metals are soft

so that hardness of the metal can be improved by adding other metal.

Ex:In preparation of ornaments of gold & silver little copper is added

into it to improve their hardness & to resist wear & tear.

2.

To increase the tensile strength:The tensile strength of pure metal is

low so it can be increased by alloying it with suitable element.Ex:

Tensile strength of iron can be increased by 10 times by addition of

1% of carbon

3.

To lower melting point: The melting point of pure metal is high. Itcan be decreased by alloying with suitable elements. Ex. Rose metal is

an alloy of bismuth, lead & tin has melting point 1000C

4. To modify colour: Colour is a natural characteristics of metal

therefore we cannot change the colour of given metal but the colour of

the metal can be modified by alloying it with suitable element.


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Ex: An alloy of brass is yellow in colour which is obtained from

copper (Red) & zinc (silvery white).

5.

To change chemical reactivity: The reactivity of some metals can be

controlled by adding some other metal to it.Ex: In sodium amalgam

(Na-Hg) alloy, the reactivity of sodium is modified by adding mercury

to it

Q. Explain any one method for the preparation of an alloy.

ORDescribe fusion method for the preparation of an alloy.

OR What is the principal method used for preparation of binary

alloy? Explain the process.

Ans: Fusion method is used for preparation of binary alloy

Process:It is the most common method used for alloy preparation.1. In this method the component metal having higher melting point is

first melted in crucible (melting pot)

2.

The other component of metal having lower melting point are added

into it in required quantity.

3. Then the surface of molten mass is covered with fine charcoal

powder to avoid oxidation of molten metal due to high temperature.

4.

Then the mixture is stirred vigorously to obtain uniform alloy.


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5.

The molten mass is then allowed to cool which gives the required

alloy.

Ex: Manufacture of Brass: Brass is a mixture of Cu & Zn. Cu ( M.P.

10890C) is melted first & then required quantity of Zn ( M.P. 4190C)

added to it which melts immediately.

Q. Describe compression method for the preparation of alloy

Ans: In this method two or more components of metal powders are uniformly

mixed. This mixture is compressed to a high pressure in a suitable mould.

The temperature of molded article is increased to just below the melting

point. Due to high temperature the tiny particles of the metal are welded

to one another producing an alloy. Ex. solder alloy of lead and tin is

prepared by this method.

Q. Explain the term calcination. What are the purposes of calcination?OR With the help of figure, explain the process of calcination. OR

How carbonate ore are concentrated by using chemical method.

Ans: Calcination:Itis the process of heating the ore strongly in the absence

of air below its melting point.

Generally carbonate, hydroxide & oxideores are concentrated by this

method.Calcination is carried out in the hearth of a reverberatory furnace by

keeping the doors closed.

Purposes of calcination:

1. To convert carbonate & hydroxide ores into oxides.

Ex: CaCO3 CaO + CO2

Limestone Calcium oxide


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2.

To remove moisture from ore.

Fe2O3 .3 H2O Fe2O3+3 H2O

3.

To remove the volatile impurities.

4.

To make the ore porous for easy reduction.

Q. How sulphide ores are concentrated by using chemical method?OR

Explain the term roasting. What are the purposes of roasting?OR

What is roasting of the ore? Give purposes of roasting.

Ans: Roasting:Itis the process of heating the ore strongly in the presence of

excess of air below its melting point.

Generally sulphide ores are concentrated by this method.

Roasting is carried out in the hearth of a reverberatory furnace by keeping

the door open.

Purposes of Roasting:

1.

To convert sulphide ores into oxides &sulphate.

Ex: 2PbS + 3O2 2PbO + 2SO2

Galena Lead oxide


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PbS + 2O2 PbSO4

Galena Lead sulphate

2. To remove the moisture from ore.

Fe2O3.3 H2O Fe2O3+3 H2O3.

To remove volatile impurities like sulphur, arsenic, antimony in the

form of their oxides

4. To make the ore porous for easy reduction.

Q. Differentiate between Calcination & Roasting.

Ans:

Calcination Roasting

It is the process of heating the

ore in absence of air.

It is the process of heating the ore in

presence of air

The purpose of calcination is to

convert carbonates & hydroxides

of metal into its oxides.

The purpose of roasting is to convert

sulphides of metal into oxides &

sulphates.

Impurities are evaporated on

heating.

Impurities are oxidized and then

evaporated.

Decomposition reaction takes

place in calcination.

Oxidation reaction takes place in

roasting

The mass become highly porous

on calcination.

The mass become less porous on

roasting.

Ex: CaCO3 CaO + CO2Limestone Calcium oxide

Ex: PbS + 2O2 PbSO4Galena Lead sulphate


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Q. Draw the flow chart for extraction of metal from its ore.


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Q. Write the composition, Properties and applications of following

alloys.

1.Alnico 2. Duralumin 3. Dutchmental 4. German silver or Nickel

silver. 5. Gun metal 6. Monel metal 7. Wood metal

Sr.No Alloy Composition Properties Uses

1 Alnico

Al = 20%

Ni = 20%

Co = 10%

Steel = 50%

1) It is highly

magnetic

2)It is corrosion

resistant.

1.For making small powerfulmagnets in Radio & T.V.

2. In making cores of

Transformers, dynamos,

Motors etc.

2 Duralumin

Al = 95%

Cu = 4%Mg = 0.5%

Mn = 0.5%

1)It has high

strength being light

in weight.2) It has good

machinability.

3) Good conductor

of heat &

electricity.

1) To fabricate the parts

automobiles.

2) It is used in making

electrical cables.3) In making surgical

instruments.

4) In making kitchen utensils,

underground railways, etc.

3 Dutch metal Cu = 80%

Zn = 20%

1) It is Golden

yellow alloy.

2)It is suitable for

all drawing and

framing work.

1)In musical instruments.

2) In cheap jewellary, Caps

of battery cell.

3) For tubes and flexible

hoses.

4German

Silver or

Nickel Silver

Cu = 60%

Zn = 20%

Ni = 20%

1) It is silver colour

alloy.

2) It has good

strength and

corrosion resistant

In salt water.

3) It is highlymalleable and

ductile.

1) In making of utensils,

coins, cheap ornaments.

(Resistors)

2) In decorative articles

(statues).

3) For making screws, bolts,

tableware etc


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5 Gun metal

Cu = 88%

Sn = 10%

Zn = 2%

1)It is silvery white,

soft alloy.

2) It is hard and

tough.

3) It is strong toresist the force of

explosion

4) It is corrosion

resistant to water

and atmosphere.

1)For making gun barrels.

2)In gears and heavy load

bearings.

3) In spare pars of boilers and

marine fittings.

4) For foundary work

6 Monel Metal Cu = 30%

Ni = 67%

Fe+Mn =3%

1) It is easily fusible

alloy

2) Its melting point

is low (700C.)

1)For making safety plugs of

pres

chemistry notes by atul waghmare government polytechnic autonomus ,aurangabad

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