class: 10th carbon and its compounds

Class: 10th Carbon And Its Compounds Chemistry

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Introduction:-There are two main classes of chemical compounds, inorganic and organic. More than a century

ago, the compounds which were of mineral origin were known as inorganic and those of vegetable or animal

origin were known as organic. For example, table salt, marble and CO2 are inorganic, whereas acetic acid,

alcohol, tartaric acid, sucrose were organic.

It was assumed that the organic compounds could be produced only by living matter, as living matter

was thought to possess a vital force.

In 1828, the German Chemist Friedrich Wohler heated ammonium cyanate, derived from inorganic

substance, and obtained the organic compound urea.

KOCN + NH4Cl KCl + NH4OCN

Potassium cyanate

O

NH4OCN NH2 C NH2

Ammonium cyanate Urea

Thus in 1850, the vital force theory was finally disproved.

Organic chemistry:- Organic chemistry is defined as the study of carbon compounds. However, there are

several exceptions:

Carbon monoxide (CO), carbonates (Na2CO3),Carbon dioxide(CO2), Bicarbonates (NaHCO3),Carbides (CaC2),

carbon disulphide (CS2), etc.

Q#1 What are organic and inorganic compounds of carbon?

Ans. Organic Compounds: are defined as compounds or carbon containing usually hydrogen and one or

more additiona1 elements oxygen, nitrogen, sulphur, halogens etc. and the branch or Chemistry which

deals with the study of organic compounds is called organic Chemistry.

Inorganic Compounds: Compounds in which carbon is linked to other atoms such as oxygen,

halogens, metals etc. and do not have C-C-bonds are called inorganic compounds of carbon.

Q#2 Differentiate between Organic and Inorganic Compounds.

Organic Compounds Inorganic Compounds

1. They are generally covalent in nature.

2. Their reaction is molecular.

3. They show isomerism.

4. They have low M.P and B.P and they

decompose on heating.

5. The usually do not dissolve in water.

6. The total number of Organic

Compounds exceeds five million.

7. They have high molecular mass and

complex structures.

8. Aqueous solutions of organic

compounds possess low electrical

conductivity.

9. They generally dissolve in organic

solvents like ether, alcohol, benzene and

chloroform.

10. They are highly combustible.

11. Certain classes possess characteristic

colours and odours.

They are ionic compounds.

Their reaction is ionic.

They do not show isomerism.

They have high M.P. and B. P. and they do

not decompose on heating.

They dissolve in water.

The total number of inorganic compounds is

50,000 approximately.

They have low molecular mass and simple

structures.

Aqueous solutions of Inorganic Compounds

high electrical conductivity.

They generally do not dissolve Inorganic

solvents.

They are non-combustible except H2, Co etc.

They are generally colourless and odourless.


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Q#3 How does carbon occur in nature?

Ans. Carbon is widely distributed in nature both in the Free State and in the combined state. In the Free State,

it occurs as diamond Graphite and Buckminister fullerence In the combined state, it occurs in form of:

1. Carbonates i.e., Limestone (CaCO3)

Magnesite (Mg C03), dolomite (CaCO3 MgCO3), malachite [CuCO3. Cu (OH)2], Siderite (FeCO3),

Calamine (ZnCO3)

2. Coal, petroleum and natural gas.

3. Proteins and fats.

4. CO2 in the air.

5. All living things, plants and animals contain organic compounds.

Q#4 What is the position of carbon atom in the periodic table. Give its electronic configuration.

Ans. Carbon is a normal element having four electrons in the outer most shell of its atom. Since carbon has 4

electrons in the outermost shell of its atom, it has been placed in-group IV of the periodic table. Carbon

is the first member of the group IV A of the periodic table, which includes Silicon, Germanium, Tin and

Lead besides Carbon.

The electronic configuration of Carbon is 1S2, 2s2, 2p2 or [He], 2s2, 2p2 or K L

2 4

It is a non metal but as the atomic number of group IV elements increases, they begin to show some

properties of metals. For example Si and Ge are semiconductors whereas Sn and Pb are metals.

Q#5 What is allotropy? Give the allotropic forms of carbon.

Ans. When an element exists in two or more forms having different physical properties but identical

chemical properties, it is called allotropy and the different forms are called allotropes, allotropic forms

or allotropic modifications.

Carbon exists in two allotropic forms: -

i. Crystalline and ii. Amorphous or Microcrystalline forms of carbon iii.Buckminster fullerene

1. Crvstalline allotropic forms of carbon: -

Two naturally occurring allotropes of carbon having well defined crystal structures are: -

i. Diamond and ii. Graphite. Due to different structures they have different properties.

2. Amorphous or Microcrvstalline forms of carbon: -

The various amorphous forms of carbon are coal, coke, charcoal, bone, blood or animal charcoal lamp

black, carbon black, gas carbon and petroleum coke.

Q#6 What is diamond? How diamonds occur? How diamonds are formed in nature? Give the

properties and

uses of diamond.

Ans. Diamond is the purest form of carbon. It is represented by the symbol C. It derives its name from Greek

word diaphane meaning transparent.

Occurance: - They are found chiefly in South Africa, Congo, Angola and Brazil. The famous

'Kohinoor' diamond was found in Wajrakarur. Diamonds are described in terms of carats (l carat =

200mg).

How diamonds are formed: - They are formed from the carbon present in the upper mantle at a depth

of over 150kms inside the Earth, under the conditions of high temperature (1500°c) and high pressure

(70,000 atm). They are brought to the surface of the earth by Kimberlite rock. Diamonds can also se

made artificially. They can be made when graphite is subjected to a high temperature (100000

atmospheres) and a very high temperature (about 37000C)

Properties of Diamond: -

1. It is the purest form of carbon.

2. It is the hardest substance known.

3. It has very high melting point 3843k and high-density 3.5 g/cm3.

4. It is a bad conductor of electricity, but good conductor of heat.

5. It has a very high refractive index (2.5), it can reflect and refract light. Therefore, it is a transparent


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substance.

6. It is insoluble in all solvents.

7. It is a colourless solid.

8. If heated strongly without excess of air it changes to Graphite.

Uses Of Diamond: 1. It is used in Jewellary as precious stone.

2. It is used for cutting glass.

3. It is used in rock drilling equipments.

4. It is used for making highly accurate thermometers because of sensitivity to heat rays. 5. It is used

for making dies for drawing thin wires from metals.

5. It is used for making dies for drawing thin wires from metals.

6. It is used for grinding hard materials.

7. It is used by eye-surgeon as a tool to remove cataract from eyes.

8. It is used for making protective windows for space satellites.

Q#7 Describe the structure of diamond.

Ans. A diamond crystal is giant molecule of C-atoms. Each carbon atom is linked to four other C-atoms by

strong covalent bonds to form tetrahedral structure.

Q#8 What is graphite? How does it occur? How can it be prepared? Give the properties and uses of

graphite.

Ans. Graphite is black and soft substance, which possess metallic lusture and has a soapy touch. Its symbol is

c. It derives its name from the Greek word Graphein meaning to write.

Occurrence:- It is found in Orissa, Rajasthan, Bihar, J&K, Sri lanka, Andhra Pradesh,

Karanatka, Canada, Tamil Nadu, and United State of America. Its occurrences is common

because formation does not require extreme conditions like excessive heat and temperature.

Preparation:- It is prepared by Acheson's process by heating powdered Coke mixed with little sand

and ferric Oxide to 3237k in an electric furnace.

Properties of graphite: 1. It is also the purest form of carbon (90-97%) of carbon)

2. It is soft and good lubricant.

3. It is dark grey having a metallic luster.

4. It is a good conductor of heat and electricity.

5. It density is 2.25gcm-3)

6. It is insoluble in water and organic solvents.

7. It can mark paper.

8. It burns on strong heating (7000C) to form CO2.

Uses of Graphite:

1. It is used as a lubricant in heavy industry.

2. It is used for making electrodes for dry cells.

3. It is used for making cores of lead pencils.

4. It is used for the manufacture of crucibles, which can withstand high temperature.


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5. It is used as moderator in atomic reactors.

6. It is used in electrotyping and electroplating.

7. It is used as covering of plaster casts.

8. Its fibres are strong, so it is used to reinforce plastic.

Q#9 Describe the structure of graphite or arrangement of C-atoms in graphite.

Ans. Graphite consists of C-atoms or sheets of C-atoms. Each carbon atom is linked to three other C-atoms

directly In the same plane by covalent bonds to form flat hexagonal rings. These rings constitute huge

sheets or layers of atoms as shown in fig. The C-C bond length in rings is 1.42A0 while different sheets

of C-atoms are held by weak Vander Waal's force at a distance of 3.4 A0

Q#10 What is Buckminster fullerene? What are their uses in future?

Ans. In 1985, scientists created a new allotrope of carbon element by heating graphite to extremely high

temperature. This is called Buckminster fullerene. It is an allotrope of carbon containing clusters of 60

carbon atoms joined together to form spherical molecules. Its formula is C60. Buckminster fullerene is a

football shaped spherical molecule in which 60 carbon atoms are arranged in interlocking hexagonal

and pentagonal rings of Catoms. There are 20 hexagonal and 12 pentagonal rings of c-atoms in its

single molecule. The structure of this allotrope resembles the frame work of dome shaped halls

designed by American architect Buckminster fullerene for large international exhibitions.

Buckminster fullerene is a dark solid at room temperature. It is a spherical carbon molecule containing

60 carbon atoms joined together which was discovered in 1985. Other spherical molecules of carbon

made up of 70, 90 and 120 carbon atoms have now been discovered . They are written as C70 , C90 and

C120 respectively.

The fullerenes have been found to be present in interstellar clouds in outer space. They have also been

found to exist in nature in the meteorite which had fallen in Germany and in ancient rocks which occur

in New Zealand and Russia.

The researches which have been done so far has suggested that in future, fullerenes and their

compounds may prove to be of great use as semiconductors, superconductors, lubricants, catalysts

electric wires and as fibres to reinforce plastic. Some of the compounds of fullerenes appear to be

active against diseases like cancer and AIDS. This can lead to finding cure for cancer and AIDS.


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Q#11 What are hydrocarbons? How are they have been classified.

Ans. The simplest organic compound containing carbon and hydrogen are called hydrocarbons.

Hydrocarbons are of two types

i. Saturated and ii. Unsaturated

Saturated hydrocarbons: are those in which all the carbon atoms are linked to one another by only

single bonds. i.e. the carbon valences are fully satisfied. These compounds contain only C-C and C-H

types of bonds. Since they are relatively inert towards most of the chemical reagents under ordinary

conditions, they are called paraffin’s (Latin parum-little affins-affinity) The IUPAC name for these

compounds is alkanes and they are represented by a general formula CnH2n+2 where

n = 1,2,3,4…

Unsaturated Hydrocarbons : A hydrocarbon in which the two c-atoms are connected by a “double

bond” or a “triple bond” is called an unsaturated hydrocarbon. These are further classified into two

types.

i. Alkenes or Olefins (containing "double bond")

ii. Alkynes or Acetylenes (“triple bond” )

Alkenes or Olefins: - Unsaturated hydrocarbons containing C=C bond in their molecule are called

alkenes. They are also called olefines (Latin, oleun = oil, ficare = to make) because their lower members

form oily products on treatment with chlorine or bromine.

They are represented by a general formula Cn H2n, where n=2,3,4...........

Names of alkenes:

1. Common name:- Alkane-ane+ylene= Alkylene.

2. IUPAC name: Alkane - ane+ene= alkene

The molecule formula, common name and IUP AC name of first six alkenes are –

N Formula Common Name IUPAC Name

1 CH2( Unstable) Methylene Methene

2 C2H4 Ethylene Ethene

3 C3H6 Propylene Propene

4 C4H8 Butylene Butene

5 C5H10 Pentylene Pentene

6 C6H12 Hexylene Hexene

N. Formula Common Name IUPAC Name

1 CH4 Methane Methane

2 C2H6 Ethane Ethane

3 C3H8 Propane Propane

4 C4H10 n- Butane Butane

5 C5H12 n- pentane Pentane

6 C6H14 n-Hexane Hexane

7 C7H16 n-Heptane Heptane

8 C8H18 n-Octane Octane

9 C9H20 n- Nonane Nonane

10 C10H22 n-Decane Decane


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Alkynes or Acetylene

Unsaturated hydrocarbon containing a Carbon-Carbon triple bond are called alkynes. They are also

called acetylenes after the name of the first member of this series called acetylene, HCCH, and a triple

bond is often referred to as the acetylenic linkage.

They are represented by a general formula CnH2n-2 , where n = 2,3,4 ...

Names of alkynes:

1. Common names: Acetylene and its alkyl derivatives.

2. IUPAC name: Alkane- ane+yne= Alkyne.

The common and IUPAC names of a few simple alkynes are given below :

N Formula Common name IUP AC Name

2 C2H2 Acetylene Ethyne

3 C3H4 Methyl-acetylene Propyne

Or Allylene

4 C4H8 Ethyl Acetylene Butyne

5 C5H8 Propyl acetylene Pentyne

6 C6H10 Butylacetylene Hexyne

Alkyl group :- The group formed by the removal of one H-atom from an alkane molecule is called an

alkyl group. e.g methyl group CH3 and Ethyl group C2H5-. They are formed by the removal of one H-

atom from methane and ethane.

The general formula of alkyl group is Cn H2n + 1. Thus alkane-ane + yl = alkyl

Alkane Alkyl group Common Name

Methane CH4

Ethane C2H6

Propane C3H8

CH3___

C2H5___

C3H7____

Methyl

Ethyl

Propyl

Q#12 Write down the molecular, structural and electronic formula of Mcthane, Ethane, Propane,

Butane, Pentane, Hexane, Heptane.

Name Formula Cn H2n+2 Structural Formula Electronic Formula

Methane

Ethane

Propane

Butane

CH4

C2H6

C3H8

C4H10

H

H C H

H

H H

H C C H

H H

H H H

H C C C H

H H H

H H H H

H C C C C H

H H H H

H

. .

H : C : H

. . H

H H

. . . . H : C : C : H

. . . .

H H

H H H

. . . . . . H : C : C : C : H

. . . . . .

H H H

H H H H

. . . . . . . .

H : C : C : C : C : H

. . . . . . . .

H H H H


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Pentane

Hexane

C5H12

C6H12

H H H H H

H C C C C C H

H H H H H

H H H H H H

H C C C C C C H

H H H H H H

H H H H H

. . . . . . . . . . H : C : C : C : C : C : H

. . . . . . . . . .

H H H H H

H H H H H H

. . . . . . . . . . . .

H : C : C : C : C : C : C : H

. . . . . . . . . . . .

H H H H H H

1. Combustion (burning): All the alkanes are combustible. They burn in air or oxygen producing

CO2 and H2O and also liberate heat in this process i.e.

CH4+ 2O2 CO2 + 2H2O, ∆ H = 890kj/mole

2. Reactivity: Alkanes are comparatively un-reactive with other chemicals because they are

saturated compounds having only single covalent bonds.

3. Substitution: Alkanes give substitution reactions due to their structural stability. They involve

the replacement of one or more H-atoms by the atoms of other elements like halogens (F,CI, Br, )

Sunlight

CH4 + CL2 CH3Cl + HCl

∆ Methyl chloride

. ∆

CH3Cl + Cl2 CH2Cl2 + HCl

Methylene Chloride

∆

CH2Cl2 + Cl2 CHCl3 + HCl

Chloroform

∆

CHCl3 + Cl2 CCl4 + HCl

Carbon tetra Chloride

Q13. What is homologous series? Write the characteristics of the member of a homologous series?

Ans. A homologous series is series of compounds in which adjacent members differ by a CH2 unit. The

individual members are called homologous. For example the homologous series of alkanes can be

represented as CnH2n + 2 while for alkenes and alkynes are CnH2n and CnH2n - 2.

General Characteristics of a homologous series:

1. All compounds in the series contain the same elements and the functional group.

2. All compounds in the series can be represented by a general formula.

3. All two consecutive members differ in their formula by a common difference of - CH2.

4. All compounds in the series can be prepared by similar methods.

5. All compounds in the series have similar chemical properties.

6. There is a gradual variation in physical properties with increasing molecular weight.

7. The difference in the molecular mass of any two adjacent homologous is 14 a.m.u.


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Q#14. a. What do you understand by Isomerism? Illustrate with examples.

b. Write the possible isomerism of butane and pentane.

Ans. There are many organic compounds that have same molecular formulae but differ in their physical and

chemical properties due to the different structural arrangement of atoms in them are called isomers or

isomerides. (Greek iso-equal, moros - parts) while the phenomenon or the process is known as

isomerism.

There two main types of isomerism -:

1. Structural or Constitutional isomerism.

2. Stereo-isomerism or Space Isomerism

Characteristics of Isomerism:

1. They have the same molecule formula.

2. They have different structural formula.

3. They have different physical and chemical properties.

Possible Isomerism of Butane (C4H10). Butane can have two structural formula as

(i) (ii)

H H H H H H H

H C C C C H H C C C H

H H H H H H

H C H

H

n- butane CH3 CH CH3

CH3

Iso butane (2 methyl propane)

Possible Isomers in pentane (C5H12)

There are three isomers of pentane named n-pentane, Iso-pentane and neo-pentane.

(i)

H H H H H

H C C C C C H

H H H H H

Or CH3 CH2 CH2 CH2 CH3 pentane (n-pentane)

(ii)

H H H H

H C C C C H or CH3 CH CH2 CH3

H H H CH3


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H C H

H Iso – pentane or 2 – Methyl butane

H

H C H

H H CH3

H C C C H OR CH3 C CH3

H H CH3

H C H Neo - Pentane

2,2 dimethyl propane

H

With an increase in the no. of C-atoms in a molecule, the number of possible structural isomers

increases. Thus there are two butanes, three pentanes, five haxanes and 75 docanes and so on.

Q#15 What are addition reactions? Give an example.

Ans. The reaction in which an unsaturated compound reacts with another substance to give a single product is

called an addition reaction. Addition reactions are given by all unsaturated hydrocarbons like alkenes

and alkynes which contain double bond or triple bond. In fact, addition reaction is the characteristic

property of unsaturated hydrocarbons e.g.

Ethene reacts with one molecule of chlorine to form a saturated compound dichlororo ethane.

C2H4 + Cl2 CH2Cl CH2Cl.

In this addition reaction, one Cl atom adds to each Catom and the double bond is reduced to single

bond.

Q#16 How do Alkenes reacts with hydrogen?

Ans. The Alkenes react with hydrocarbon when heated presence of catalyst like nickel to form saturated

hydrocarbons called Alkanes. For example, ethane reacts with hydrogen when heated in the presence of

nickel catalyst to form ethane.

C2H4 + H2 Ni C2H6

Heat

This is called hydrogenation. It is used to prepare vegetable ghee (Vanaspati) from vegetable oils.

Q#17 What is meant by functional group? Explain with ann example.

Ans. A functional group is an atom or group of atoms in a molecule that gives the molecule its characteristic

chemical properties.

The alcohol group OH group present in ethanol C2H5OH is an example of a functional group the

functional group is the action group while the hydrocarbon portion remains inert. Some of the

important functional groups present in organic compounds are Halo group, Alcohol group, Aldehyde

group, Ketone group, Carboxylic group, Alkene group, Alkyne group, ether group, ester , amino and

amide group.

Q#18 Write down the IUPAC system of Nomenclature.

Ans. In early days of organic chemistry, each new compound was given an individual name. Such a name

was based on the source, some property or some other common reason.

With the rapid growth of organic chemistry, the number of compounds increased fantastically (about 3

million). It became impossible to give common names to such a large number of compounds.


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In 1957, the international union of pure and applied chemistry evolved a scheme for giving systematic

names to organic compounds on the basis of their structure. This is known as IUPAC system

(pronounced as eye-you-pack)

One organic compound can have only one IUPAC name. Knowing the IUPAC name of a compound,

we can at once write its structural formula.

Q#19 Write the IUPAC rules for naming Alkanes.

Ans. Rule1:- Select the longest continuous carbon chain.

Rule2:- Name the longest chain.

CH2 CH2 CH CH3

CH3

The longest chain is butane

Rule3:- Number the longest chain:- The numbering is started from that end which will give

lowest value to substituent.

CH3 CH2 CH CH3 and not CH3 CH2 CH CH3

CH3 CH3

Rule4:- Identify the substituent:-

Name the substituent and indicate its position by the number of the C-atom to which it is attached.

Rule5:- Perfix the position number and name of the substituent onto the parent name.

CH3 CH2 CH CH3

CH3

2- methyl butane

Rule6:- Identify the substituent by names and position number. Use prefix di, tri, tetra etc.

CH3 CH3

CH3 CH CH2 CH CH3 CH3 CH2 C CH2 CH3

CH3 CH3

2,4- dimethyl pentane 3, 3 – dimethyl pentane.

Rule 7:-When two or more different substituents are present. These names are arranged in alphabetic

order

CH3 CH2 CH CH2 CH CH2 CH2 CH3

CH3 C2H5

5- ethyle-3-methyloctane

IUPAC RULES For Alkene C = C


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The alkene group is a carbon – carbon double bond. The compounds containing alkene group are known as

alkenes. For example.

CH3

CH3 CH = CH2 CH3 C = CH2

Propene 2-methyl propene

CH3

CH3 CH2 CH = CH2 CH3 C = CH CH2 CH3

1-Butene 2-methyl -2- pentene

CH2 = C =CH2

1,2-propadiene

IUPAC Rules for Alkynes:-

The alkynegroup is a carbon-carbon triple bond. The compounds containing alkyne group are known as

alkynes.

H H

HC CH H C C C C H

H H

Ethyne 2- Butyne

CH3 C C CH2 CH CH3

CH3

5- methyl – 2-hexyne

CH C C CH

1,3- Butadiyne

Nomenclature of Haloalkanes or Alkyle halides

Haloalkanes are compounds which contain carbon- halogen bonds. When one hydrogen atom of an alkane is

replaced by a halogen atom, we get haloalkanes. i.e.

CH4 -H CH3Cl -

Methane +Cl Chloromethane

(methyl chloride)

The general formula of haloalkanes is CnH2n+1 – X where X represents Cl, Br or I. In the IUPAC method,

haloalkanes are named after the parent alkane by using a prefix to show the presence of the halo group such as

chloro (-Cl), Bromo(-Br) and Iodo (-I) group.


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H

The IUPAC name of (CH3Cl) is chloromethane CH3Cl or CH3 Cl or H C Cl

H

The common name of CH3Cl is methyl chloride. The IUPAC name of (C2H5Cl) is chloroethane

C2H5Cl or CH3 CH2 Cl or

H H

H C C Cl

H H

The common name of C2H5Cl is ethyle chloride.

Br CH3

CH3 CH CH3 CH3 CH2 CH CH2 Cl

2- Bromo propane 1- chloro – 2-methyl butane

Nomenclature of Alcohols:- Alcohols are compounds in which a hydroxyl group (-OH) is bonded to a

saturated carbon. When one hydrogen atom of an alkane is replaced by a hydroxyl group, we get alcohol.

CH4 -H CH3OH or ROH

Methane +OH Methyl alcohol (or methanol) Where R is the alkyl group.

The general formula of alcohols is CnH2n+1 – OH

In the IUPAC method, the last ‘e’ of the parent alkane is replaced by ‘ol’ to indicate the presence of OH group.

i.e. Alkane-e +ol Alkanol

The IUPAC name of CH3OH is methanol while as the common name is methyl alcohol. Similarly the IUPAC

name of C3H7OH is propanol and the common name is propyl alcohol.

OH CH3

CH3 CH CH3 CH3 CH CH2 CH2 OH

2-propanol 3- methyl – 1- butanol

Nomenclature of aldehyde:- Aldehydes are carbon compounds in which an aldehyde group (-CHO) group is

attached to a carbon atom. The general formula of aldehyde is CnH2nO, when n=1,2,3…….

In the IUPAC method, the last ‘e’ of the parent alkane is replaced by ‘al’ to indicate the presence of aldehyde

group.

i.e. Alkane – e + al = Alkanal.

O

The IUPAC name of HCHO is methanal HCHO or H CHO or H C H


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The common name of methanal is formaldehyde. The IUPAC name of CH3CHO is ethanal whereas its

common name is acetaldehyde. Similarly, the IUPACname of C2H5CHO is propanal and its common name is

propionaldehyde.

H H O

CH3CH2 CHO or CH3 CH2 CHO or H C C C H

H H

Nomenclature of ketones:-

Ketones are compounds in which the carboxyl group (C=O) is bonded to two organic groups. A ketone must

contain at least 3-carbon atoms in its molecule. The simplest ketone is CH3COCH3 (propanone) the general

formula of ketone is CnH2nO.

Where n= 3, 4, 5………

In the IUPAC method, the last ‘e’ of the parent alkane is replaced by ‘one’ to indicate the presence of a ketone

group.

The IUPAC name of CH3COCH3 is propanone and its common name is Acetone (dimethyl ketone)

O H O H

CH3COCH3 or CH3 C CH3 or H C C C H

H H

The IUPAC name of CH3 CO C2H5 is butanone and its common name is Ethyl methyl ketone. Similarly, for

CH3COC3H7, the IUPAC name is pentanone and the common name is methyl propyle ketone.

Nomenclature of carboxylic acids:-

Carboxylic acids are compounds which contain the carboxylic acids are compounds which contain the carboxyl

group(-COOH). They are also called organic acids.

They occur in fatty acids, butter, ghee etc. the general formula of organic acid is Cn H2n+1 COOH or

RCOOH. Where R is an alkyl group. The name carboxyl is derived from carboxyl (C=O) and hydroxyl (-OH)

In the IUPAC system, the carboxylic acids are named as alkanoic acids. The IUPAC name of an

organic acid is obtained by replacing the last electron of the parent alkane by ‘oic’ and adding the word ‘acid’

to the name.

The IUPAC name of HCOOH is methanoic acid and its common name is formic acid.

The first five organic acids are given below:

Formula Common name IUPAC

n=0 HCOOH Formic acid Methanoic acid

n=1 CH3COOH Acetic acid Ethanoic acid

n=2 C2H5COOH Propanoic acid Propanoic acid

n=3 C3H7COOH Butyric acid Butanoic acid


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n=4 C4H9COOH Valeric or Camroic acid Pentanoic acid.

Chemical properties of carbon compounds

Combustion:- The process of burning of a carbon compound in air to give carbon dioxide, water heat and light

is known as combustion.

All the alkanes are combustile. When they are ignited in the presence of excess oxygen, they burn to

form CO2 and H2O with the liberation of large amount of heat energy.

CH4 + 2O2 Heat CO2 + 2H2O + Heat + light

When alkanes are burnt in insufficient supply of oxygen, they form carbon monoxide and carbon. For example:

2CH4 + 3O2 2CO + 4H2O

CH4 + O2 C + 2H2O

The unsaturated hydrocarbons (Alkanes and alkynes) do not undergo complete combustion and hence burn with

luminous, yellow sooty flame and produce carbon monoxide and water because they contain higher parentage

of carbon which does not get oxidized completely in the insufficient oxygen present in air.

However, if unsaturated hydrocarbons are burned in pure oxygen, then they will burn completely and

produce extremely high temperature. For example, when acetylene burn in pure oxygen, it produces extremely

high temperature (30000C) which is used for welding and cutting of metals.

Substitution reaction:- Alkanes are comparatively uncreative due to their structural stability. They however,

undergo substitution reaction. In the substitution reaction, one or more hydrogen atoms of a hydrocarbon are

replaced by the atoms of other elements like halogens (F , Cl , Br, I)

For example methane reacts with chlorine to give methyl chloride and HCl in presence of ultraviolet light or

diffused sunlight or at a temperature of 300 – 4000C.

CH4 + Cl2 Sunlight CH3Cl + HCl

Methyl chloride

(Chloro methane)

CH3Cl + Cl2 CH2Cl2 + HCl

Methylene chloride

(Di chloro methane)

CH2Cl2 +Cl2 CHCl3 + HCl

Chloroform

(Trichloro methane)

CHCl3 + Cl2 CCl4 + HCl

Carbon tetrachloride


15

(Tetra chloro methane)

Addition reaction:- The reaction in which an unsaturated compound reacts with another substance to give a

single product is called an addition reaction. Addition reactions are given by all unsaturated hydrocarbons like

alkenes and alkynes which contain double bond or triple bond. In fact, addition reaction is the characteristic

property of unsaturated hydrocarbons-. For example,

Ethene reacts with one molecule of chlorine to form a saturated compound dichloroethane

C2H4 + Cl2 CH3 Cl CH3 Cl

1,2 dichloro ethane

In this addition reaction, one Cl atom adds to each C-atom and the double bond is reduced to single bond.

Addition reaction of ethene with hydrogen:- Ethene reacts with hydrogen, when heated under pressure and

in the presence of Ni , Pt , or Pd as catalyst to produce saturated hydrocarbons. A hydrogenation reaction

carried in this process is called catalytic hydrogenation.

CH2 = CH2 + H2 Ni CH3 CH3

Ethene Ethane

The process of hydrogenation is used to prepare vegetable ghee (vanaspati) from vegetable oils.

Hydrogenation of oils:- Hydrogenation reaction is used in the manufacture of vanaspati ghee from vegetable

oils. The vegetable oils such as groundnut oil, cotton seed oil and mustard oil contain double bonds in their

molecules. When reacted with hydrogen in the presence of nickel as catalyst, they are converted into vanaspati

ghee which is solid at room temperature like butter or ghee.

Vegetable oil + H2 Ni Vegetable ghee

(Unsaturated hydrocarbon) Vanspati ghee or

(Saturated hydrocarbon)

Oxidation reaction:- When alkenes react with cold dilute alkaline solution of potassium permanganate

(KMNO4), ethyle glycol is formed.

i.e. C2H4 KmnO4 CH2 CH2

Ethane H2O

OH OH

Ethylene glycol.

Since the bright purple colour of Kmno4 disappears during the reaction. It is used as a test for the presence of a

double bond.

Q#20 Give the preparation, properties and uses of ethanoic acid (Acetic acid).

Ans. Ethanoic acid (acetic acid) is well known in the form of vinegar. Vinegar contains about 5-8 % of

ethanoic acid. It is present in biological fluids and plant extracts.

Preparation:- Ethanoic acid can be prepared by several methods.


16

i) By enzymatic oxidation of ethanol:- It can be obtained by the oxidation of ethanol by air in the

presence of acetobactor enzyme.

CH3 CH2OH (l) + 2[O] acetobactor CH3COOH (aq) + H2O(l)

Ethanol From air Ethanoic acid

( 5 – 8%)

ii) It can be prepared by the hydrolysis of alkyl cyanide

CH3CN + 2H2O CH3COOH + NH3

iii) Methanol when reated with carbon monoxide in the presence of iodine-rhodium catalyst gives ethanoic

acid.

CH3OH(l) + CO(g) I2 –Rh CH3COOH

Methanol Carbon monoxide Ethanoic acid

Physical properties:- Some common physical properties of ethanoic acid are described below:-

1). At ordinary temp, ethanoic acid is a colourless liquid with a strong pungent smell and sour taste.

2). On cooling below 16.50C it forms ice-like crystals that is why, it is named as glacial acetic acid.

3). It has a corrosive action on the skin and causes blisters.

4). It is miscible with water due to the formation of hydrogen bonds with water molecules.

5). It dissolves sulphur, iodine and many other organic compounds.

Chemical properties:- The main chemical reactions given by ethanoic acid are described below:

1) With water:- In aqeous solutions it ionizes to produce H3O+ and CH3COO- ions.

CH3COOH(l) + H2O (l) CH3COO- (aq) + H3O+ (aq)

Ethanoic acid Ethanoate ion Hydronium ion

2) Action on ltmus:- Ethanoic acid is acidic in nature being acidic in nature, ethanoic acid terms blue

litmus solution red.

3) With sodium hydroxide:- It reacts with strong alkali such as NaOH giving sodium ethanoate and

water.

CH3COOH (aq) + NaOH(aq) CH3COONa(aq) + H2O (l)

Ethanoic acid Sodium hydroxide Sodium ethanoate Water

4) With metals:- Ethanoic acid reacts with active metals to form metal ethanoates and H- gas.

2CH3COOH(aq) + 2Na(s) 2CH3COONa (aq) + H2(g)

Ethanoic acid Sodium Sodium ethanoate Hydrogen gas

5) With sodium carbonate and sodium bicarbonate:-

Ethanoic acid decomposes sodium bicarbonate and sodium carbonate with a rapid evolution of CO2 gas.


17

Na2CO3 (aq) + 2CH3COOH(aq) 2CH3COONa(aq) + H2O (l) +CO2 (g)

Sodium carbonate Ethanoic acid Sodium ethanoate Water Carbon dioxide

6) Reaction with alcohols:- Ethanoic acid reacts with alcohols in the presence of dehydrating agents e.g.

concentrated H2SO4 to form ester.

CH3COOH(l) + C2H5OH(l) CH3COOC2H5 + H2O

Ethanoic acid Ethanol Ethyl ethanoate.

The reaction of carboxylic acid with an alcohol to form an ester is called esterification.

Tests for carboxylic acids:-

1) Sodium bicarbonate test:- The organic compound to be tested is put in a test tube and a little amount

of sodium bicarbonate is added to it. Evolution of CO2 gas shows that the given compound is

carboxylic acid.

2) Ester test for acids:- The organic compound is warmed with some ethanol and few drops of

concentrated sulphuric acid. A sweet smelling ester shows that the organic compound is a

carboxylic acid.

Uses of ethanoic acid:-

1) Ethanoic acid is used in the manufacture of various dyes, perfumes and a rayons.

2) Salts of ethanoic acid are used in paints and also in certain medicines.

3) It is used for making synthetic vinegar which is used in pickles etc.

4) It is used as a solvent.

5) It is used for coagulating the latex.

6) It is used for making white lead.

7) It is used for making cellulose acetate.

8) It is used for making acetone.

Q.21 Give the preparation, properties and uses of ethyl alcohol (ethanol).

Ans. Ethyl alcohol (C2H5OH) is the second number of the homologous series of alcohols. Ethyl alcohol is

the alcohol of wine, bear, whisky and similar beverages. Ethyl alcohol is also known as grain alcohol,

since it can be prepared from starchy grains.

Preparation:- It is prepared on a large scale by the fermentation of sugars present in molasses (cheap

source of glucose, fructose and sucrose) in the presence of yeast. The enzymes invertase and zymase

present in the yeast act as catalyst in converting sugar into ethanol and C02.

Invetase

C12H22O11 + H2O C6H12O6 + C6H12O12

Sucrose Glucose Fructose

(in molasses)

zymase

C6H12O6 2C2H5OH + 2CO2 (g)

Glucose/Fructose Ethyl alcohol

1. It is obtained by reacting ethene with water in the presence of phosphoric acid (H3PO4) at a


18

temperature of 3000C and 60 -70atm.

H3PO4

C2H4 + H2O C2H5OH

Eyhene water 3000c, 60-70 atm Ethanol

Physical properties:-

1. It is a colourless, volatile liquid with a characteristic pleasant odour and

burning taste.

2. It boils at 78°C and freezes at -1180C.

3. Its specific gravity is 0.789

4. It is soluble in water as well as in all organic and inorganic solvents.

5. It is a neutral compound and has no effect on the colour of litmus.

6. It is lighter than water.

7. It is poisonous in nature.

8. It is a covalent compound and hence does not conduct electricity.

Chemical Properties of Ethanol: 1. Reaction with Na or K :- Ethyl alcohol reacts with sodium to form the corresponding

ethoxides and H - gas.

2 C2 H5OH + 2 Na 2C2H5ONa + H2 (g)

Sodium Ethoxide

2. Reaction with Phosphorus halide:- It reacts with phosphorus halide to give ethyl halide.

C2H5OH + PCl5 C2H5Cl + POCl3 + HCl

Ethyl chloride phosphorous oxychloride

3. Combustion:-It burns in air with a blue flame to form CO2 and water vapour.

C2 H5 OH + 3O2 Combustion 2 CO2 + 3 H2O + Heat + light

4. Oxidation:- Alkaline potassium permanganate or acidified dichromate

solution oxidizes ethanol to ethanoic acid ( acetic acid)

CH3CH2OH + 2[O] Alkaline KmnO4 CH3COOH + H2O

Or acidified K2Cr2O7 Ethanoic acid.

5.reaction with ethanoic acid (Esterification reaction):- Ethanol when

heated with ethanoic acid in the presence of concentrated H2SO4 to form a

sweet smelling ester (ethyl ethanoate).

CH3COOH + C2H5OH Conc.H2SO4 CH3COOC2H5 + H2O

Ethanoic acid Ethanol Ethyl ethanoate Water

In this reaction, conc. H2SO4 acts as a catalyst as well as a dehydrating

agent.

6.Dehydration:- When ethanol is heated with excess of conc. Sulphuric

acid at 1700 C, it gets dehydrated to form ethane.

CH3 CH2OH Conc H2SO4 CH2 =CH2 +H2O

Ethanol 1700 C Ethene Water


19

Tests for an alcohol

1. Sodium metal test:- Add a small piece of sodium metal to the organic

liquid , taken in a dry test tube. If bubbles of hydrogen gas are

produced , it indicates that the given organic liquid is an alcohol.

2. Ester tests for alcohol:- The organic compound is warmed with some

ethanoic acid and a few drops of conc. Sulphuric acid. A sweet smell

indicates that the given organic compound is an alcohol.

Uses: 1. It is used in the manufacture of alcoholic drinks, like whisky, wine, bear etc.

2. It is used in the manufacture of drugs and perfumes.

3. It is used in thermometers and spirit lamps.

4. It is used as a preservative for biological specimens.

5. It is used in the manufacture of acetaldehyde, acetic acid, ethyl chloride and ethyl acetate.

6. It is used as an industrial solvent.

7. It is used in hospitals as an antiseptic to sterilize wounds and syringes.

8. It is used in varnishes.

9. It is used in the manufacture of synthetic rubber.

10. It is used as a substitute of petrol in scooters and cars.

11. It is used as antifreeze for automobile radiators.

Q.22 What are soaps? How will you manufacture the soap?

Ans. Soaps are the substances that are used for cleaning and washing actions. They are sodium or potassium

salts of fatty acids like oleic acid. stearic acid, palmitic acid, lauric acid and myristic acid. Ordinary

soaps are the products of hydrolysis of oils and fats with sodium hydroxide.

1. Sodium Stearate (CI7H35COONa): It is the sodium salt of fatty acids (saturated acids called

stearic acid CI7H35COOH). A higher portion of saturated salts gives hard soaps.

2. Sodium Palnitate (CI5H31COONa): It is the sodium salt of long chain saturated fatty acids called

Palmitic acid C15H34COOH.

3. Sodium Oleate (CI7H33COONa): It is a sodium salt of a long chain unsaturated fatty acids called

Oleic acid CI7H33COOH. Higher proportion of this salt yields soft soaps.

Preparation of Soaps:- Soap is prepared by heating fats or oils with sodium or potassium hydroxide

solution (Lye). The process of making soaps by the alkaline hydrolysis of oils and fats is called

sapnofication.

Heat

Oil or fat + Alkali Soap + Glycerol

C3H5(COOC17H35)3 + 3NaOH 3C17H35COONa (Soap) + C3H5(OH)3 (Glycerine)

During heating and boiling the mixture should be constantly stirred. A punch of NaCl and few

flower petals should be added, the mixture is heated until thick paste is obtained. The soap separates

out from the solution and thus the crust of soap is removed and allows to set and harden. The harden

mass is then cut into desired shapes and sizes and are thus packed for marketing.

Preparation of soap at home or in the laboratory: Add 10ml of a 40% NaOH solution to 10ml of

cotton seed oil in a beaker. Boil the mixture with continuous stirring till a thick paste is obtained.

Add some hardening agent i.e. Na2CO3 to harden the soap.

Heat

Oil (fat) + Base Soap + Glycerol

When the reaction is complete, both the products are in the form of aqueous solution. To precipitate

out the soap, add some NaCl, the soap thus obtained is dried and cut into bars and cakes.


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Cleansing action of soap or how soap works: Cleansing soap function by acting amulsifying agents

which means that oil and grease to be removed from the surface of skin or fabric are broken into smaller

droplets. Each one of the small droplets is surrounded by a film of soap which is washed away with

water.

The soap consists of two parts i.e., the long hydro carbon part (C17H35) of the soap that is oil

soluble (liphopholic) and the other charged end (COONa) is water soluble (hydrophilic). As soap water

is poured over the skin or a dirty garment, the hydro-carbon tails of the soap molecules per into the oil,

while the negative head is held in water. The grease layer is then separated from skin by rubbing or

from garment by tumbling and stirring.

Advantages of Soap:

1. Soap is an excellent cleansing agent having 100% bio degradability.

2. Micro –organisms present in sewage water easily oxidize soap to CO2 and water and hence

there can be no pollution problem.

Disadvantages of soap:

1. It can be used in soft water but not in hard water, because a large amount of soap is wasted

in reacting with calcium and magnesium ions in hard water to form a scum.

2. It cannot be applied in acetic medium as it sticks to the fabrics and hence causes problem

during dyeing and drying.

Q.23 What are synthetic detergents and write advantages of synthetic detergents over soaps?

Ans. Soaps are good cleansing agents yet they become ineffective if the water is hard. Scientists have

developed synthetic cleansing agents and which are not prepared from vegetable oil. These cleansing

agents are called detergents.

Synthetic detergent ions of the sodium salt of a long chain benzene sulphonic acid or the sodium

salt of a long chain alkyl hydrogen Sulphate.

Sodium Lauryl sulphate (C12H25OSO3Na) is an example of synthetic detergent. It does not form

Scum with the ions Ca2+ or Mg2+ and hence washes well even in hard water.

Advantages of detergents over Soaps:

1. Synthetic detergents are used even with hard water whereas soaps are not suitable for use with hard

water.

2. Synthetic detergent is prepared from hydrocarbons of petroleum so they help us save vegetable oils

for human consumption.

3. Detergents can be used in acidic solutions whereas soaps cannot be used in the acidic medium

4. Detergents have more cleaning action than soaps.

5. Detergents are more soluble in water than soaps.

6. Detergents may be used for cotton as well as woolen clothes.

Q24. Give the differences between soap and synthetic detergents.

Soaps Detergents

1. Soaps are the salts of the long chain fatty

acids and the ionic group is COO - Na+.

2. Soaps are not suitable for washing with

hard water.

3. They are prepared from animal fats or

vegetable oils.

4. Soaps are biodegradable.

1. They are the sodium salts of long chain

benzene sulphonic acids and ionic

group in a detergent is SO3Na+

2. They can be used both in hard and soft

water.

3. They are prepared from the

hydrocarbons of petroleum.

4. They are non-biodegradable.

Class:10th Metals And Non Metals Chemistry

1

There are 118 elements at present. Each of the elements is unique. The discovery of the elements started about

8000 years ago, when people obtained shiny materials from the rocks by heating. By 1940, all the 92 naturally-

occurring elements had been discovered.

Classification of elements

All elements are classified into three categories: - Metals, Non Metals, and Metalloids. Metals are placed on the

left-hand side, in the middle and at the bottom of the periodic table. Non metals are placed on the right hand side

and in the upper middle part of the periodic table. Metalloids are located at the left end of the nonmetals. On the

extreme right side of the periodic table are the noble gases.

Q What are metals? Give examples.

Ans. Metals are the elements (except hydrogen) which form positive ions by losing electrons. Thus, metals are

electropositive elements. Metals are lustrous (shiny) malleable and ductile. They possess high density and

are good conductors of heat and electricity. The oxides of metals are basic in nature. Some examples of

metals are Iron, Aluminium, Copper, Zinc and Sodium. Metals generally have 1 to 3 electrons in the

valance shell of their atoms.

Q What are non metals? Give examples.

Ans. The elements which tend to form anions by gaining electrons are termed as non metals. Thus, non metals

are electronegative elements. Non metals have no lusture. They are non malleable and non- ductile. Non

–metals are brittle. Most of the nonmetals possess low density and they are poor conductors of heat and

electricity. The oxides of non metals are acidic or neutral in nature. Some examples of non metals are

carbon, silicon, phosphorous, iodine, bromine, hydrogen, nitrogen, oxygen, fluorine, etc. Non metals

usually have 4 to 8 electrons in the outermost shell of their atoms.

Q What are metalloids? Ans. The elements which behave like metals as well as non-metals are called metalloids. Arsenic, Tin, Bismuth,

Silicon, Antinomy, Germanium are common examples.

Q Write down the physical properties of metals.

Ans. The important physical properties of metals are given below:

a) Metals are Malleable:- This means that metals can be hammered into very thin sheets. Gold and

Silver are the most malleable metals. Both Gold and Silver can be hammered into foils much

thinner than the thinnest paper. Copper, Aluminium and Iron are also highly malleable.

b) Metals are ductile:- This means that metals can be drawn into than wires. All metals are not

equality ductile. Gold, silver and copper are among the most ductile metals. For example, we can

draw a wire of about 200m length from 100mg of silver. Zinc, arsenic and antimony are not ductile.

c) Metals are good conductors of heat:- Metals are good conductors of heat. Silver metal is the best

conductor of heat. Copper and aluminium metals are also very good conductors of heat. The

poorest conductor of heat is lead.

d) Metals are good conductors of electricity:- Metals allow or permit electricity to pass through

them easily. They offer very little resistance to the flow of electric current. Silver is the best

conductor of electricity. Copper is the next best conductor of electricity. Gold, aluminium and

Tungsten are good conductors of electricity after silver and copper. Mercury and iron are not good

conductors of electricity.

e) Metals are lustrous:-Metals are lustrous (shiny) and can be polished. For example, gold, silver and

copper metals have metallic luster and they can be polished.


2

f) Metals have high tensile strength:- Metals are very strong (except sodium and potassium). They

bear a lot of stress.

g) Most metals except sodium and potassium are hard:- Sodium and potassium metals can be easily

cut with a knife. Osmium is hard enough to scratch glass.

h) Metals have high melting points and boiling points:-Metals have high melting points and boiling

points (except sodium and potassium metals which have low melting and boiling points). The

melting point of Gallium and Cesium metals are so low that they start melting in hand.

Metal Copper Iron Silver Sodium Potassium

M.P/0C 1083 1539 960.8 97.9 63.8

B.P/0C 2310 2450 1955 882 760

i) Metals have high densities except sodium and potassium:- The densities of some common metals

are given below Metal Copper Iron Silver Gold Sodium Potassium

Density g/cm3 8.94 7.86 10.47 195 0.97 0.86

j) Metals are sonorous:- Metals when hit by a hammer produce a characteristic metallic sound.

k) All metals except mercury are solids.

l) Metals usually have a silver or grey colour except copper and gold. Copper has a reddish-brown

colour whereas gold has a yellow colour.

m) Metals can form alloys with other metals. For example, copper and zinc dissolve in each other to

form an alloy called brass.

Q Write down the physical properties of non metals.

Ans. 1) Non metals are neither ductile nor malleable:- Non metals cannot be drawn into wires and beaten

into leaves/ sheets because they are brittle. They break up into pieces when pressed hard or

hammered. For example, sulphur and red phosphorous are brittle. The property due to which non-

metals break up on hammering is called brittleness.

2) Non metals are insulators: - Non metals do not conduct heat and electricity. This is because they

do not have free electrons. However, diamond is a non metal which is a good conductor of heat and

graphite is a non metal which is a good conductor of electricity.

3) Non metals do not have lustre:- Non metals are not shiny. However, graphite and iodine are the

only non metals which have metallic lustre. As a result non metals cannot be polished.

4) Non metals are generally soft except diamond which is the hardest natural substance known.

5) Non metals have low tensile strength:- They can be easily broken. For example, when a large

weight is placed on a graphite sheet, it gets snapped (breaks).

6) Non metals have low melting and boiling points:- For example, the m.p. of sulphur is 1150C and

m.p of white phosphorous is 440C . However, graphite, which is a non metal, has a high m.p.

(37000C).

7) Non metals may be solid, liquid or gaseous at room temperature.

8) Non metals have low densities:- Non metals are light substances for example, the density of

sulphur is 2g/cm3. Only non –metal iodine has, however, high density.

9) Non metals are non sonorons :- Non metals do not produce sound when hit with an object.

10) Non metal have many different colours:- For example, sulphur is yellow, phosphorous is white or

red. Graphite is black; chlorine is yellowish green whereas hydrogen and oxygen are colourless.

11) Non metals show allotropy:- Some non metals exist in more than one allotropic forms. For

example, phosphorous exists in five different forms; sulphur exists in three forms etc.


3

Q Give the chemical properties of metals. Ans. The chemical reactivity of different metals is different depending upon their nature and the reaction

conditions. Some of the important chemical properties of metals are given below:-

a) Reaction with oxygen:- All metals combine with oxygen to form metal oxides. The reactivity of a

metal towards oxygen depends upon its nature. For example,

i) Sodium reacts with oxygen at room temperature to form sodium oxides.

4Na + O2 room temp. 2Na2O

Sodium Oxygen Sodium oxide

ii) Magnesium on heating in air gives magnesium oxide.

2Mg + O2 burn/heat 2MgO

Magnesium Oxygen Magnesium oxide

iii) Copper is a metal less reactive metal. It reacts with oxygen slowly only on prolonged strong

heating.

2Cu + O2 strong heating 2CuO

Copper Oxygen Copper (ii) oxide

The order of reactivity of these metals with oxygen is

Na > Mg > Zn > Fe > Cu

Most reactive least reactive

b) Metal oxides are basic in nature. Soluble metal oxides react with water to give metal hydroxides

(alkalies). The solutions of metal oxides in water turn red litmus blue and colourless phenolphthalein to

pink. For example, sodium oxide (Na2O) reacts with water to give sodium hydroxide.

Na2O + H2O 2NaOH

Sodium oxide Sodium Hydroxide

(base oxide) (alkali)

Some metal oxides e.g. aluminium oxide (Al2O3), Zinc oxide (ZnO) show both acidic as well as basic

character. Such metal oxides are called amphoteric oxides. For example,

ZnO + H2SO4(dil) ZnSO4 + H2O

Zinc oxide Zinc sulphate

(basic oxide) (Salt)

ZnO + 2NaOH Na2ZnO2 + H2O

Zinc oxide Sodium zincate

Acidic oxide Salt

c) Reaction with water:- When a metal reacts with water, than a metal oxide or metal hydroxide and

hydrogen gas are formed. Different metals react with water under different conditions. Some metals react

with cold water, whereas some other metals react only with hot water or steam. For example,

1) Sodium reacts vigorously with cold water to give hydrogen gas

2Na (s) + 2H2O 2NaOH + H2(g)

Sodium Cold water Sodium hydroxide


4

2) Magnesium reacts only with hot boiling water to form magnesium oxide and hydrogen gas

Mg(s) + H2O MgO + H2(g)

Magnesium Boiling Magnesium oxide

3) Red hot iron reacts with steam to liberate hydrogen

3Fe + 4H2O Fe3O4 + 4H2

Red hot iron steam iron (II, III) oxide

4) Copper metal is very unreactive and does not react even with steam. The order of reactivity of some

metals with water is

Na > Mg > Al > Zn > Fe > Cu

Most reactive least reactive

d) Reaction with dilute acids:- Metals react with dilute hydrochloric acids to give metal chloride and

hydrogen gas. However, the less reactive metals, such as copper, silver; gold, etc. do not displace hydrogen

from dilute acids. Some metals react rapidly, some metals react on heating, whereas other metals do not

react with dilute acids at all.

For example,

1. Sodium metal reacts violently with dilute hydrochloric acid to form sodium chloride and hydrogen gas.

2Na(s) + 2HCl(g) 2NaCl(g) + H2(g)

Sodium Hydrochloric acid Sodium chloride Hydrogen

2. Aluminium metal at first reacts slowly and then rapidly with dilute hydrochloric acid to form

aluminium chloride and hydrogen gas.

2Al (s) + 6HCl(aq) 2AlCl3 (aq) + 3H2(g)

Aluminium Hydrochloric acid Aluminium chloride Hydrogen

3. Zinc reacts with dil HCl at moderate rate to give zinc chloride and hydrogen gas.

Zn + 2HCl(dil) ZnCl2(aq) + H2(gas)

Zinc hydrochloric acid Zinc Chloride Hydrogen

4. Copper does not react with dil HCl or dil. H2SO4 but slowly dissolves in dil H2SO4 in the presence of

air.

2Cu + 2H2SO4(dil) + O2 from air 2CuSO4(aq) + 2H2O

The order of the reactivity of these metals with dilute acid is

Na> Mg > Al > Zn > Fe > Cu

e) Reaction of metals with chlorine:- Most metals react with chlorine to form chlorides. Metals chlorides

are mostly ionic (or electrovalent) compounds. Metal chlorides have high melting point and boiling point.

For example,

Sodium readily reacts with chlorine o form an ionic chloride called sodium chloride.


5

1. 2Na(s) + Cl2(g) heat 2NaCl(s)

Sodium Chlorine Sodium chloride.

2. Ca(s) + Cl2(g) heat CaCl2(s)

Calcium Chloride Calcium Chloride

3. Mg(S) + Cl2 (g) heat MgCl2(s)

Magnesium Chlorine Magnesium Chloride

4. Cu(s) + Cl2(g) heat CuCl2(s)

Copper Chloride Copper (II) chloride

f) Reaction with hydrogen:- Most metals do not react with hydrogen . Only highly electropositive metals

such as sodium, potassium, calcium and magnesium react with hydrogen to form hydrides. Metal hydrides

are ionic compounds.

i) 2Na + H2 heat 2NaH

Sodium Hydrogen Sodium Hydride

ii) Ca + H2 heat CaH2

Molten Calcium Calcium hydride

iii) Mg + H2 high temp. MgH2

Pressure Magnesium hydride

iv) Aluminium, Zinc, Iron, Copper do not react with hydrogen.

Q What is the activity series of metals?

Ans. The arrangement of metals in a vertical column in the order of decreasing reactivity is called activity series

of metals. The activity series is also called reactivity series.

The more reactive metals have greater tendency to lose electrons. So, more reactive metals are

more electropositive or more metallic in nature. Therefore the electropositive character of metals decreases

as we go down from top to the bottom in the activity series of metals.

The activity series of some common metals is given below:

Potassium K Most reactive metal

Sodium Na

Calcium Ca

Magnesium Mg

Aluminium Al

Zinc Zn

Iron Fe

Tin Sn Decreasing chemical reactivity

Lead Pb

Hydrogen H

Copper Cu

Mercury Hg

Silver Ag

Gold Au

Platinum Pt least reactive metal


6

From the activity series, it is clear that the metals which occur above hydrogen in the activity series are more

reactive than hydrogen and those metals which occur below hydrogen in the reactivity series are less reactive

than hydrogen.

g) Reaction of metals with salt solution (Metal displacement reaction)

A reaction in which a non reactive (or more electropositive) metal displaces a less reactive (or less

electropositive) metal from its salt solution is called a metal displacement reaction.

Some metal displacement reactions are given below:

a) Reaction between zinc metal and copper sulphate solutions:- When a strip of zinc metal is put in copper

sulphate solution, than zinc displaces copper from copper sulphate solution and a colourless zinc sulphate

solution is formed and red –brown copper metal is deposited on the zinc strip.

CuSO4 + Zn ZnSO4 + Cu

Copper sulphate Zinc Zinc sulphate Copper

Colourless (Red)

b) Reaction between iron and Copper Sulphate solution:- Iron displaces copper from copper sulphate

solution.

Fe(s) + CuSO4 (aq) FeSO4(aq) + Cu(s)

More reactive metal displaced metal

Q Give the chemical properties of non metal?

Ans. Some general chemical properties of non metals are described below:

i) Electronegative character:- Non metals are electronegative elements. They have a tendency to

accept electrons and form negatively charged ions (anions) e.g.

½ Cl2 (g) + e Cl-

Chlorine Chloride ion

½ O2 (g) + 2e O2-

Oxygen Oxide ion

ii) Reaction with oxygen:- Non metals react with oxygen to give covalent oxides. Such oxides are either

neutral or acidic in nature. Acidic oxides of non metals dissolve in water to form corresponding acids.

Acidic oxides turn blue litmus red. Some examples are given below:

Nitrogen reacts with oxygen under different conditions to form five different oxides. For example,

2N2(g) + O2(g) 2N2O(g) (neutral)

Nitrogen Oxygen nitrous oxide

N2 + O2 2NO

Nitrogen oxygen Nitric oxide (neutral)

2N2(g) + 3O2(g) 2N2O3(g) (acidic)

Dinitrogen trioxide

N2(g) + 2O2(g) 2NO2(g) (acidic)

Nitrogen dioxide


7

2N2(g) + 5O2(g) 2N2O5(g) (Acidic)

Dinitrogen pentoxide

N2O5 reacts with water to give nitric acid

N2O5(g) + H2O(l) 2HNO3(aq)

Dinitrogen pentoxide Nitric acid

Similarly, sulphur on burning on air form two oxides I.e.

S(s) + O2(g) burn SO2(g)

Sulphur dioxide (acidic)

2S(s) + 3O2(g) burn 2SO3(g)

Sulphur trioxide (acidic)

iii. Reaction with Halogens:- Non metals react with halogens to give covalent halides which do not

conduct electricity in pure state. For example,

H2 (g) + Cl2(g) 2HCl(g)

Hydrogen Chlorine Hydrogen Chloride

P4 (g) + 6Cl2(g) 4PCl3(l)

Phosphorous Chloride Phosphorous Trichloride

iv. Reaction with Hydrogen: - Non metals react with hydrogen to form covalent hydrides. The hydrides of

non metals do not conduct electricity. They may be acidic basic or neutral. For example,

H2(g) + S(l) H2S(g)

Hydrogen Sulphur Hydrogen Sulphide

(Weakly acidic)

2N2(g) + 3H2(g) 2NH3

Nitrogen Hydrogen Ammonia

2H2(g) + O2(g) electric spark 2H2O(l)

Water (neutral)

The hydrides of non metals are either gases or liquids.

v. Reaction with Acids:- Non metals do not displace hydrogen from dilute acids because non metals are

electron acceptors and are not able to give electrons for the reduction H+. Thus carbon, Sulphur,

Phosphorous, etc. do not react with dilute HCl or dilute H2SO4 to give H- gas. However, sulphur reacts

with concentrated oxidizing acids (nitric acids) to give sulphuric acids.

S(s) + 6NO3 (aq) H2SO4(aq) + 6NO2(g) + 2H2O(l)

Sulphur Conc.Nitric Acid Sulphuric acid Nitrogen dioxide

vi) Reaction of Non Metals with salts solution:- A more reactive non metal displaces a less reactive non

metal from its salt solution for example,

Cl2(g) + 2NaBr(aq) 2NaCl(aq) + Br2(aq)

Chlorine Sod.Bromide Sod.Chloride Bromine


8

Q What are general uses of metal?

Ans. Some general uses of metals are described below:

1. Copper and Aluminium: - Copper and aluminium are very good conductors of electricity. So, copper and

aluminium are used for making electrical wires and cables. Aluminium is also used for making cooking

utensils. ALuminium foils are used for packaging of medicines, food materials, etc.

2. Iron: Iron is the most widely used metal. Its uses, however, mainly depend upon its carbon content. For

example,

i. Cast iron is used for manufacturing wrought iron and steel. It is generally used for making stove

burners, gutter pipes, railway sleepers, etc.

ii. Steels are used for the manufacture of permanent magnets, engine parts, utensils, surgical equipments,

springs, gears, drive shafts, armour plates, etc.

iii. Wrought iron is used for making anchors, wire ropes, bolts, chains and agricultural appliances.

3. Zinc is used for the galvanization of iron. Tin is used for tinning of iron plates/ sheets and copper/ brass

utensils. Thus, zinc and tin are used for protecting iron from rusting.

4. Nickel and chromium are mainly used for electroplating and for the manufacture of stainless steel. Nickel

is also used as a catalyst in many industrial processes.

5. Gold and silver are used for making jewellery and for decorative purposes.

6. Sodium, titanium and zirconium are used in atomic energy and space science projects. Zirconium is used

for making bullet-proof alloy steels.

7. Mercury is used in thermometers and barometers.

8. Titanium is used in

i. Aerospace

ii. Aircraft frames and engine

iii. Military hardware

iv. Marine equipment

v. Chemical reactors

vi. Chemical industries

vii. Atomic energy and space science projects.

9. Titanium due to its special applications is considered as a strategic metal. These applications of titanium

are due to its

i. High tensile strength

ii. Lightness

iii. Resistance to corrosion

iv. High melting and boiling points.

Uses of Common Non –Metals:- Some general uses of Non Metals are:

Uses of silicon

Silicon is extensively used in the electronic and computer industries to make devices, such as transistors,

microchips and solar cells.

It is used to manufacture silicones, which are used for making waterproof clothes, greases and polishes, and

insulating material for electrical appliances.

It is used to make silicon carbide, a very hard substance used in grinding tools.

Uses of Sulphur

It is used in the manufacture of sulphuric acid, which is used in several industrial processes.

It is used in vulcanization of rubber, which makes rubber hard enough to be used in tyres,

It is used to make special concrete called sulphur concrete.

It is used to skin ointments because of its fungicidal properties.

Being an insecticide and fungicide, it is used to spray fruit trees against pests and diseases.


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Uses of phosphorous

Phosphorous is used in making match boxes and in the fireworks industries.

It is used in the manufacture of phosphate fertilizers.

Uses of Graphite

Graphite is used in making electrodes in dry cells and electric arcs. It is also used as a lubricant.

Uses Of Hydrogen

It is used for the manufacture of ammonia gas, which is used to manufacture fertilizers such are urea and

ammonium sulphate.

It is used for hydrogenation of vegetable oils to manufacture vanaspati.

It is used in the extraction of metals such as copper, lead and tin.

It is used in the manufacture of industrial chemicals such as methanol

Oxy- hydrogen flame, obtained by burning hydrogen in oxygen is used for cutting and welding metals.

Hydrogen is considered to be a non- polluting fuel of the future. Considerable amount of research is being

carried out to use it efficiently as a fuel.

Q How do metals and non metals differ in their physical properties

Ans. The main points of difference between the physical properties of metals and non metals are given in table.

Comparison between physical properties of metals and non metals

Metals Non Metals

1. Metals are good conductors of heat and

electricity.

2. Metals are malleable and ductile.

3. Metals are lustrous and can be polished.

4. Metals except mercury are solids and hard.

5. Metals have high melting and boiling

points.

6. Metals have high densities.

7. Metals are sonorous.

8. Metals possess high tensile strength.

1. Non metals are non conductor of heat

and electricity. Graphite, however, is a

good conductor of heat and electricity.

2. Non metals are brittle, i.e. nonmetals

are neither malleable nor ductile.

3. Non Metals are non lustrous. Graphite

and iodine, however, have metallic

lustre.

4. Non metals are soft solids, liquids or

gases.

5. Non metals have low m.p. and b.points.

6. Non metals have low densities.

7. Non metals are non sonorous.

8. Nonmetals possess low tensile strength.

Q How do metals and nonmetals differ in their chemical properties.

Ans. The main points of difference between the chemical properties of metals and non metals are give in table

Comparison between chemical properties of metals and non metals

Metals Non Metals

1. Metals form basic oxides some of which

form alkalies.

2. Metals displace hydrogen from acids.

3. With chlorine, metals from chlorides

which are ionic compounds.

4. With hydrogen, few metals form hydrides

which are ionic (electrovalent) in nature.

5. Metals are reducing agents.

1. Nonmetals form acidic or neutral oxides.

2. Nonmetals do not displace hydrogen

from acids.

3. Nonmetals with chlorine form chlorides

which are covalent in nature.

4. Nonmetals with hydrogen form stable

covalent hydrides.

5. Non Metals are oxidizing agents except

carbon and hydrogen. Carbon and

hydrogen are good reducing agents.


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Q Give reason why gold and silver often occur in native state?

Ans. The metals at the bottom of the reactivity series are the least reactive and hence they are found in native

state in nature as free metals. Gold and silver are chemically least reactive and hence not affected by air,

water or other chemicals under ordinary conditions.

Q How do metals occur in nature?

Ans. The metals occur in nature in two ways:

a) Elemental State:- The metals are said to be in native state, if they are found in their elementary

form. Only a few less reactive metals like gold, silver, copper, platinum and bismuth are found in

native state as free metals.

b) Combined State:- The metals are said to occur in the combined state if they are found in nature in

the form of their compounds. Such as oxides, carbonates, sulphides and sulphates.

Q Define Metallurgy?

Ans. The various processes involved in the extraction of metals from their ores followed by their refining are

known as metallurgy.

Q Define some of the terms used in the extraction of metals.

Ans. i) Minerals:- The metallic compounds occur in nature in the earth’s crust along with a number of

rocky and other impurities are known as minerals.

E.g. Zincite (ZnO) , Cuprite (Cu2O), Copper glance (Cu2S).

ii) Ore:- The naturally occurring minerals from which metals can be conveniently and cheaply

extracted are called ores.

For examples copper occurs in nature in the form of several minerals like cuprite, copper glance,

copper pyrites and malachite, but copper pyrite is considered as the most economical mineral for the

extraction of the metal. Hence copper pyrites as the chief ore of copper.

iii) Gangue or matrix:- The unwanted impurities such as mud, stones , sand ,etc which are mixed

with ore are called gangue or matrix e.g. basic impurities like CaO , FeO. etc. and acidic impurities

like SiO2, P2O5 etc.

Q Distinguish between minerals and ores.

Ans. The main differences between a mineral and an ore are given below:

Minerals Ores

1. The natural materials in which the

metals or their compounds are found

in nature are called minerals.

2. Some minerals contain a good

percentage of metals whereas others

contain a small percentage of the

metals.

3. Some minerals contain

objectionable impurities which

hamper the extraction of metals.

4. All the minerals cannot be used to

extract metals. That is, all the

minerals are not ores.

1. These minerals from which metals can

be extracted conveniently and profitably

are called ores.

2. All ores contain a good percentage of

metals.

3. An ore does not contain any

objectionable impurities.

4. All the ores can be used to extract

metals.


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Q Name the various steps involved in the extraction of a metals from its ore?

Ans. The various steps involved in the extraction of a metal from its ore are:-

i) Concentration of ore (dressing of ore).

ii) Conversion of concentrated ore into metal oxide.

iii) Reduction of metal oxide to obtain metal.

iv) Refining of impure metal.

Q Describe brief the general metallurgical operations.

Ans. The various processes involved in the production of metals from their ores are described below:

a) Crushing and Grinding Of The Ore: - The process by which the huge lumps of ores are broken

down into small pieces in the jaw crushers is called crushing. They are further pulverized in stamp

mill or ball mill to convert them into powdered form so that the chemical changes which have to

take place at the later stage becomes easier.

b) Concentration Or Benefication Of The Ore: - The removal of impurities from the powdered ore

is known dressing or concentration of the ore. Concentration of the ore can be carried out in the

following ways depending upon the nature of the ore and also the impurities present in the ore, this

is done by physical and chemical methods.

Physical Method:

i) Gravity separation process or levigation or hydraulic washing:- This method is used for the

concentration of those ores whose particles are much more heavier than gangue particles. In this

method, the powdered ore is washed with running stream of water. The lighter impurities are

washed away leaving behind the heavier ore particles. The ore of tin and lead metals are very

heavy, so they are concentrated by the hydraulic washing methods.

ii) Froth floatation process:- This process is especially suitable for sulphide ores. This process is

based on the fact that sulphide ore particles are wetted by oil whereas gangue particles are wetted by

water. In this process, the powdered ore is put in tank full of water and some pine oil is added to it.

The water in the tank is agitated by blowing in compressed air when front is formed. The sulphide

ore particles stick to the froth bubbles and rise to the surface of water with froth. The gangue

particles remain behind at the bottom of tank. In order to reap froth, ethyl xanthate is mixed in

water. The sulphide ores of zinc, copper and lead metals are concentrated by this method.

Magnetic separation:- This process is usually employed for the separation of magnetic impurities from

non- magnetic ore. In this method, the powdered ore is dropped over the belt revolving around the rollers,

one of which is magnetic. The magnetic roller attracts the magnetic part of the ore and they are collected in

the form of heap near it. The non- magnetic part of the ore flies off and forms a heap away from the

magnetic part.

This process is largely used for the extraction of the ores such as Tinston (SnO2) ferrous Tangstate or

wolfram (FeWO4), Chromite (an ore of chromium) etc.


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Chemical Separation: Leaching:- It is a chemical method for the concentration of the ore. In this process

the powdered ore is dissolved in certain acids, bases or other suitable reagents. The impurities remain

undissolved as sledge. The solution of ore is filtered and the ore is recovered by precipitation or

crystalisation.

For example:- Bauxite (AL2O3 . 2H2O) is concentrated with an aqueous solution of NaOH when alumina

(Al2O3 ) dissolves to form soluble sodium meta Aluminate (NaAlO2), while the other oxides remain

undissolved as insoluble red mud.

Al2O3.2H2O + 2NaOH 2NaAlO2 + 3H2O

Ore Base Soluble

(Alkaline)

The solution is filtered to remove insoluble impurities like silica and other oxides. The filtrate is diluted

with water and stirred to give a precipitate of aluminium hydroxide. The later is separated and ignited to

get the pure alumina.

NaAlO2 + 2H2O heat Al(OH)3 + 2NaOH

2Al (OH)3 heat Al2O3 + 3H2O

Production of Metal from the Concentrated Ore:- Before the concentrated ore is subjected to final

metallurgical operations in order to get the metal in the free state, the preliminary treatment may be necessary

i.e.

a) To get rid off the impurities which would cause difficulties in the later stages.

b) To convert the ore into oxide of the metal.

Conversion of Concentrated Ore into Metal Oxide:- The metal oxide can be extracted from the concentrated

ore by calcination and roasting.

Calcination:- It is a process of heating the ore in limited supply of air below its melting point, the process

involves.

i) The removal of volatile impurities.

ii) The removal of moisture.

iii) The conversion of carbonate ores to oxides.

iv) Mass becomes porous.

ZnCO3 . MgCO3 Calcination CaO + MgO + 2CO2

Zinc carbonate Calcium Oxide Magnesium Oxide


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CaCO3 . MgCO3 Heat CaO + MgO + 2CO2

Roasting:- It is the process in which the ore alone or mixed with other materials is heated in the presence of air

below its melting point.

During Roasting:-

i) Volatile impurities are removed.

ii) Sulphide ores are converted to oxides.

iii) Free S, As and Sb are removed as SO2 , As2O3 and Sb2O3 respectively.

2ZnS + 3O2 heat 2ZnO + 2SO2

Zinc sulphide zinc oxide

2Pbs + 3O2 heat 2PbO + 2SO2

Both calcination and roasting are performed in reverberatory furnace.

Reduction of Metal Oxide to Metal:- The free metals are obtained from metal oxides by the process of

reduction. The metal oxides can be reduced to free metals on three ways:

a) Reduction by heat alone.

b) Chemical reduction by using carbon or aluminium.

c) Electrolytic reduction.

Reduction by heat alone:- The less reactive metals can be produced just by heating their compounds.

e.g. HgS + O2 heat Hg + SO2

Mercuric Sulphate Mercury

Reduction by Carbon (Smelting):- In this process, the roasted or calcinated ore is mixed and heated with coal

or coke to high temperature. This is known as smelting .

e.g. heat

Fe2O3 + 3C 2Fe + 3CO

PbO + C heat Pb + CO

ZnO + C heat Sn + 2CO

Smelting is done in a blast furnace in presence of a flux. Flux is a substance which reacts with the impurities to

form a fusible product called slag.

Flux + Impurities Slag

Acidic flux (silica, borax) is used for removing the basic impurity while basic flux (CaCO3 , MgCO3 , Fe2O3

etc) is used to remove the acidic impurity i.e.

P4O10 + 6CaO 2Ca3(PO4)2

Acidic Impurity Basic Flux Slag

CaO + SiO2 CaSiO3

Basic Impurity Acidic Flux Slag


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Reduction by Aluminium ( Aluminothermic reduction):- Certain oxides like Fe2O3 , Cr2O3 , Mn3O4 are not

easily reduced with carbon. In such cases, aluminium is used as a reducing agent. Examples

a) Cr2O3 + 2Al Al2O3 + 2Cr

b) 3MnO2 Heat Mn3O4 + O2

Reduction by Precipitation (Hydrometallurgy):- This method is applied for the extraction of less electro

positive metals (Cu , Ag and Au) by adding more electropositive metals like zinc, iron etc.

a) CuSO4 + Fe FeSO4 +Cu

2K [Ag (Cn)2] + Zn K2[Zn(Cn)4] + 2Ag.

Electrolytic Reduction (Electrometallurgy):- Highly electro-positive metals like Na, K , Ca , Mg , Al etc. are

extracted by the electrolysis of their oxides, hydroxide or chlorides in fused state. The metal is deposited at the

cathode where as chlorine gas is evolved at the anode. Thus,

a) 2NaCl electrolysis 2Na + Cl2

Sodium Chloride Sodium metal Chlorine gas

b) MgCl2 electrolysis Mg + Cl2

2Al2O3 electrolysis 4Al + 3O2

Refining of Metals: - The metals obtained by any one of the metallurgical operations still contain some

impurities like:

Other metals originally present in the ore.

Unreduced oxides or sulphides of metals

Residual slag or flux, and

Non metals like carbon, silicon, phosphorous, etc.

The process of removal of impurities from the crude metal is termed as refining, some of the methods are:

Electrolytic refining of metals:- It means refining by electrolysis. Many metals like copper, zinc, tin, lead,

chromium, nickel, silver and gold are refined electrolytically. For the refining of an impure metal by

electrolysis.

a) A thick block of the impure metal is made anode.

b) A thin strip of the pure metal is made cathode.

c) A water soluble salt (of the metal to be refined) is taken as electrolyte can passing electricity, impure metal

from the anode goes into the solution as ions due to oxidation and pure metal gets deposited on cathode due

to reduction of metal ions, the impurities are settled down below the anode as anode need.


15

Extraction of Aluminium:- Aluminium is the most abundant element (8.31%) by weight in the earth’s crust

after oxygen and silicon being reactive in nature it always occurs in combined state. It occurs as oxide, fluoride

and silicate. The important ores are:-

1) Bauxite :- Al2O3 . 2H2O

2) Cryolite :- Na3AlF6

3) Feldspar:- KAlSi3O8

Extraction of aluminium from bauxite involves two stages. In the first stage, pure alumina (Al2O3) is obtained

from bauxite and in the second stage electrolysis of molten alumina is carried out to give an aluminium metal.

First Step:- Purification or concentration of bauxite ore is carried out by Baeyer’s process as described below.

In this process bauxite ore is treated with hot concentrated solution of sodium hydroxide. The aluminium oxide

present in bauxite ore dissolves in sodium hydroxide solution forming sodium aluminate, Na AlO2, leaving

behind iron oxide which is present as an impurity and is removed by filtration.

Al2O3 + 2NaOH 2NaAlO2 + H2O

b) Sodium aluminate solution is then diluted with water and Al (OH)3 is added to enhance precipitation.

Thus, it acts as seeding agent. Sodium aluminate gets hydrolyzed to form a white precipitate of aluminium

hydroxide.

NaAlO2 + H2O Al(OH)3 + H2O

c) The precipitation of aluminium hydroxide is separated by filtration, washed dried and then heated strongly

to get pure aluminium oxide(Alumina).

2Al(OH)3 Al2O3 + 3H2O

Alumina

Thus, impure aluminum oxide of bauxite ore has been converted into pure aluminium oxide called alumina.

Second Step:- (Electrolysis of Aluminium Oxide) As Aluminium cannot be extracted by reducing alumina by carbon because carbon has less attraction for

oxygen than aluminium metal. So aluminium metal is obtained by the electrolytic reduction of aluminium oxide as

described below:

Pure alumina is then dissolved in fused cryolite, NaAlF6 and electrolyzed in an iron tank lined with gas carbon.

The carbon lining serves as the cathode while as a number of carbon rods dipping in the fused mass serve as the

anode. The function of cryolite is to lower the melting point of alumina. When aluminium oxide is melted, it

produces free aluminium oxide. Al3+ and oxide ions O2-

Al2O3 2Al3 + 3O2-

On passing electric current through molten aluminium oxide. The following reactions take place at the two

electrodes.

At Cathode: Al3+ + 3e- reduction Al

Thus aluminium metal is formed at cathode and collects at the bottom of the iron tank.

At Anode: O2- - 2e- oxidation O (Oxygen atom)


16

Thus, oxygen gas is liberated at the carbon anode. The oxygen gas reacts with the carbon of carbon anode to form

carbon dioxide, due to which the carbon anode is gradually burns away or consumed. Cryolite remains unchanged

during the electrolysis and fresh alumina is added to the iron tank from time to time.

Extraction of copper:- Copper occurs as native copper as well as in combined state. Native copper is found in

large quantities in U.S.A. Mexico, Russia, China and Chile. The principle ores of copper are:-

1) Copper pyrites :- CuFeS2

2) Cuprite or ruby copper:- Cu2O

3) Copper glance:- Cu2S

4) Malachite: - Cu (OH) 2, CuCO3.

5) Azurite:- Cu(OH)2 , 2CuCO3

Out of all these, copper pyrites is the principal ore of all copper from which copper is extracted copper pyrites is

the mixture of copper sulphide and iron sulphide.

CuFeS2 CuS + FeS

The various steps involved in the process are:-

1) Concentration: - The finally powdered ore is concentrated by froth flotation process. In this process, the

powdered ore is put in a tank full of water containing small amount of pine oil. The water in a tank is agitated

by blowing air as a result, Froth is formed. The particles of the sulphide ore are preferentially wetted by oil

and rise to the top in the form of froth which is skimmed off and gangue particles remain at the bottom of the

tank, on keeping, froth settles down and concentrated sulphide ore is formed.

2) Roasting:- The concentration ore is treated strongly in excess of air furnace, as a result concentrated ore is

oxidized to copper oxide and sulphur dioxide.

2CuS + 3O2 CuO + 2SO2

3) Smelting:- When a good amount of copper sulphide has been converted into copper oxide, then after some

time the supply of air for roasting is stopped. In the absence of air copper oxide is formed above reacts with

the remaining copper sulphide to form copper metal.

CuS + 2CuO Cu + SO2

The process in which copper oxide reacts with copper sulphide to form copper metal is called bessemerization.


17

4) Electrolytic refining of copper:- In this case a thin sheet of pure metal is made as cathode and a block of

impure metal is made as anode. Both the electrodes are placed in an acidified copper sulphate solution.

When the electric current is passed through the solution, impure copper from the anode goes into the

solution and pure copper from the solution gets deposited on the cathode. The impurities get collected

below the anode as anode mud.

Q Describe the process of extraction of iron.

Ans. Extraction of iron: - Iron is the second most abundant metal occurring in the earths crust. Being react

with nature it occurs in combined state. The chief ores of iron are:

i) Hematite

ii) Magnetite

iii) Siderite

Iron is usually extracted from the hematite ore. The process of extraction involves the following steps:

i) Concentration:- The ore crushed and is broken into small pieces of about 1 inch in size. The

crushed ore is concentrated by gravity separation process in which it is washed in water to remove

clay, sand etc.

ii) Calcination :- The ore is then calcinated. During calcinations, the carbonates present in the ore are

decomposed to their oxides(ferrous oxide is converted to ferric oxide).

FeCO3 FeO + CO2

4FeO + 3O2 2Fe2O3

iii) Smelting:- This is also referred to as reduction. After this process, the ore mixed with coke and

limestone in the ratio of 4: 2:1. This resulting mixture is then introduced into a blast furnace.

The blast furnace is essentially a cylindrical tower about 100- 120 feet. It is made up of firebricks and has

an outer casing of steel plates.

Air is introduced into the blast furnace. Carbon (coke) burns to form CO2 which rises up through the layers

of coke to give CO. Iron oxide is reduced to iron by CO. Limestone’s acts as flux and combines with

impurities like SiO2 to form a slag which being lighter floats on the top and is removed. In blast furnace,

there are zones of different temperatures where in different reactions takes place.

1) Zone of combustion:- At the lower portion of the furnace, there is a zone of combustion. Here

coke (carbon) burns to give carbon dioxide gas.

C + O2 CO2 + 94.000 cals.

This is an exothermic reaction and heat so produced raises the temperature to about 15550C. This region is

known as zone of combustion.

2) Zone of heat absorption:- Just above the zone of combustion, there is a zone of heat absorption. Carbon

dioxide produced above rises up through the layers of coke to give carbon monoxide (CO). Thus, CO2 is

reduced to CO.

CO2 + C 2CO + 39.000 cals.

This is an exothermic reaction and due to the loss of heat, the temperature falls to 1200- 1300 c. This

region is called zone of heat absorption.


18

3) Zone of reduction:- In the upper portion of furnace carbon monoxide reduces the oxide of iron to metallic

iron at 600 -750c.

Fe2O3 + 3CO 2Fe + 3CO2

The iron obtained from the base of blast furnace is impure iron is known as cast iron or pig iron.

Q What is corrosion? What are the necessary conditions for the corrosion to take place? How can

corrosion be prevented?

Ans. Slow destruction of metals due to their interaction with the environment is called corrosion.

Q What are the necessary conditions for the corrosion to take place?

Ans. For corrosion to take place, the following two conditions are necessary:

Presence of oxygen/ air.

Presence of moisture or water vapour.

Rate of corrosion is affected by the following factors:

Electropositive nature of metal

Purity of the metal.

Presence of reactive gases in the air.

Presence of electrolytes in water.

Temperature.

Q How can corrosion be prevented?

Ans. Corrosion of metals can be prevented in many ways. Some commonly used methods are described below:

a) By surface coating: Corrosion of metals can be prevented by coating their surfaces with any of the

following materials:

By applying oil, grease, paint or vanish on the surface.

By coating/ depositing a thin layer of any other metal which does not corrode. For example,

iron surface can be protected from corrosion by depositing a thin layer of zinc, nickel or

chromium on it.

b) By connecting metal to a more electropositive metal:- A metal can be protected from corrosion

by connecting it to a more electropositive metal. As long as the more electropositive metal is there,

the given metal does not get corroded. For example, iron can be protected from the corrosion by

connecting it to zinc or magnesium.


19

Q What is meant by rusting of iron?

Ans. Rusting of iron is the most common type of corrosion. Iron when exposed to moist air ( air containing

large quantity of water vapors) gets covered with a layer of brown powdery material.

The reaction which describes the rusting of iron is,

4Fe(s) + 3O2(g) + xH2O Fe2O3. H2O(s)

Iron oxygen water hydrated ferric oxide

From air (rust)

Rust is soft, porous and powdery substance. It falls off from the surface of iron of its own.

Q What are the necessary conditions for rusting of iron? How can rusting be prevented?

Ans. The necessary conditions for rusting of iron:- For rusting to take place the following conditions must be

fulfilled:

Presence of oxygen

Presence of water/ moisture

Since, the moist/wet air contains both oxygen as well as water, hence rusting of iron takes place when iron

is exposed to moist air.

Q What accelerates the rate of rusting?

Ans. The following factors accelerate the rate of rusting:

i) The presence of gases, such as carbon dioxide (CO2), oxides of sulphur (SO2 , SO3) and oxides of

nitrogen( NO, NO2) in air increase the rate of rusting.

ii) The presence of electrolytes, such as sodium chloride, in water increases the rate of rusting. It is

because of this reason that iron rusts faster in sea water than in distilled water.

iii) The presence of impurities of less electropositive metals in iron increases the rate of rusting.

Q How can rusting be prevented?

Ans. Rusting of iron can be prevented by the following methods:

a) By surface coating:- Rusting of iron can be prevented by coating the iron surface with oil, grease,

paint and vanish.

b) By galvanization of iron:- Iron can be protected from corrosion by coating it with a thin layer of

zinc. The process of depositing a thin layer of zinc on iron is called galvanization.

c) Galvanization is done by either of the following methods:

i) By spraying molten zinc on the iron surface.

ii) By dipping iron sheet / object into molten zinc.

d) By tinning:- Tin(Sn) is not attacked by air and water. Tin is non- toxic. So, the containers used in

the packaging of food items are coated with tin. Coating of any reactive metal with a thin layer of

tin is called tinning.

e) By alloying:- Iron can be prevented from corrosion by alloying iron with chromium and nickel.

Stainless steel (iron 74%; chromium 18% and nickel 8%) is corrosion resistant.

f) By connecting iron to a more electropositive metal: Corrosion of iron can be prevented by

connecting iron to a highly electropositive metal, such as magnesium.


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Alloy:

A homogeneous mixture of two or more metals (or a non-metal) obtained by melting them together, is

called an alloy.

Types of Alloys:-

Alloys have been divided into the following three types:-

i) Ferrous alloys:- An alloy in which iron is present as one of the constituents is called a ferrous alloy.

ii) Non- ferrous alloys:- An alloy which does not contain iron as one of the constituents is called a non-

ferrous alloy.

iii) Amalgams:- An alloy containing mercury as one of the constituent metal is known as amalgam.

E.g. Sodium amalgam, Zinc amalgam.

Properties Of Alloys:-

The physical properties of the alloys are, generally, different from the physical properties of the constituent

metals. Alloys are prepared to develop certain specific properties not possessed by constituent elements.

The main objectives of alloy making are:-

1. Change In Hardness:- Some alloys can be made harder than constituent metals. Eg when an alloy of aluminium and magnesium

is made, it is harder than both the metals.

i) When 0.5% to 1.5% of cabon is added to iron, it forms steel which is harder than iron.

ii) Gold is a soft metal. It is hardened by the addition of copper so as to make jewelry.

2. Resistance to Corrosion:

a) Iron metal corrodes to form rust in the moist air. However, if it is alloyed with chromium and nickel, it

form stainless steel which is resistant to corrosion.

b) Monel metal is an alloy of copper, nickel and iron which does not corrode in the moist air.

3. Change In Melting Point:-Some alloys have lower melting points than constituent metals. For example,

solder, an alloy of tin and lead, has lower melting point than both the constituent metals.

4. Change In Electric Conductivity:-Generally, metals are good conductors of electricity. However,

nichrome, an alloy of nickel, chromium and iron, is poor conductor of electricity. It is used in making

heating elements of electrical devices, such as heaters, ovens, toasters, geysers, etc.

5. Change In Chemical Reactivity:- Sodium is a highly reactive metal. Its reactivity can be reduced by

making its alloy with mercury i.e. amalgam.

6. Change In Tensile Strength:- Chrome steel prepared by mixing iron ( 96 – 98 %) and chromium (4 – 2%)

has high tensile strength and is used for making oxales, ball bearing and cutting tools.

7. To Produce Good Casting:- Type metal, an alloy of lead (70%), antimony (20%) and tin (10%) has good

casting properties and hence is used for making priting type.

8. Change In Colour:- Aluminium is silvery white while copper is brown but aluminium bronze, an alloy of

aluminium (95%) and copper (5%), has beautiful yellow colour and is used for making coins, picture

frames and cheap jewellery.


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Alloying Of Gold:-

Pure gold is seldom used for making ornaments, as it is soft metal with a high melting point. Thus, it is

alloyed with other metals like copper, silver, brass, cadmium, etc. This makes the gold workable at lower

temperature. Furthermo re, it increases the hardness and hance, the ornaments formed from alloying gold, do

not get deformed easily.

How ever, alloying the gold reduces the purity of gold. Thus, in order to know the purity of gold in the

article of alloyed sample, it is expressed in carat/ karat, where/ carat/ karat = 4.1666 g per 100 g of alloy.

For example, 22 carat/ karat ornament of alloyed gold contains 4.1666 x 22 = 91.666% of pure gold. Much

the same way, 24 carat/ karat gold contains 4.1666 x 24 = 99.998 or 100% of gold.

Some common Alloys, their Composition, Properties and Uses.

Alloy Composition Properties Uses

1. Steel Iron (99.95%),

Carbon (0.05%)

Hard, tough and strong Construction of ships, bridges,

vehicles etc.

2. Stainless steel Iron (74%),

Chromium (18%),

Nickel (8%)

Hard and doesn’t rust. For making cutlery, utensils and

surgical instruments.

3. Brass Copper (80%),

Zinc (20%)

Malleable, strong, resists

corrosion, can be easily cast.

For making utensils, screws,

nuts and bolts.

4. Bronze Copper (90%),

Tin (10%)

Very strong and highly

resistant to corrosion.

For making statues, coins,

medals, ship’s propeller etc.

5. German silver

(does not contain silver)

Copper (60%),

Zinc (20%)

Nickel (20%)

Shines like silver, resistant to

corrosion.

For making resistance wires,

electroplating etc.

6. Duralumin Aluminium (95%)

Copper (4%)

Magnesium (0.5%),

Manganese(0.5%)

Light, strong, ductile and

resistant to corrosion.

For making aeroplanes,

automobile parts, pressure

cookers etc.

7. Magnalium Aluminium (95%),

Magnesium (5%)

Very light and hard. For making light instruments

and balance beams.

8. Aluminium Aluminium (95%),

Copper (5%)

Shines like silver. For making coins, picture

frames, cheap jewellery.

9. Solder Lead (50%) ,

Tin (50%)

Has lower melting point than

either lead or tin.

For joining electrical wires

together.

class: 10th carbon and its compounds

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