Carbon and Its Compounds Class-8 Dalal Simplified ICSE Chemistry Solutions Chapter-9

Carbon and Its Compounds Class-8 Dalal Simplified ICSE Chemistry Solutions Chapter-9, Carbon and Its Compounds Dr Viraf J Dalal Middle School Allied Publishers Solutions. Chapter-9. We Provide Step by Step Solutions to Questions and Answers of Dr Viraf J Dalal Middle School Chemistry Allied Publishers. Visit official Website CISCE for detail information about ICSE Board Class-8.

Carbon and Its Compounds Class-8 Dalal Simplified ICSE Chemistry Solutions Chapter-9

Board ICSE
Class 8th
Subject Chemistry
Book Name Dalal New Simplified
Chapter-9 Carbon and Its Compounds
Unit-1 Carbon and Its Compounds
Topic Solution of exercise questions
Session 2023-24


Carbon and Its Compounds Class-8 Dalal Simplified ICSE Chemistry Solutions Chapter-9

Question: 1. Differentiate between the two branches of chemistry – organic chemistry & inorganic chemistry with suitable examples.


Organic chemistry Inorganic chemistry
The study of specific carbon compounds which includes compounds mainly of carbon, hydrogen & oxygen. Includes the study of oxides of carbon, carbonates, bicarbonates, metallic carbides etc.
Examples: Hydrocarbons e.g. – methane-CH4 & ethane-C2H6; Acids e.g. acetic acid- CH3COOH; Alcohols – e.g. methyl alcohol – CH3OH Examples: Carbon monoxide – CO; Carbon dioxide – CO2; Calcium carbonate – CaCO3 Calcium bicarbonate – Ca(HCO3)2; Carbonic acid – H2CO3 etc. Other compounds of carbon include – sugar & starch, fuels & synthetic fibres.

Question: 2. State how carbon occurs in the free state and in the combined state.

Answer: In the free state —

  • carbon occurs free in nature in the crystalline form [i.e. crystal] as diamond & graphite & in the
  • amorphous form [impure] as coal formed below the earth’s surface.

In the combined state —

  • Carbon occurs as carbon dioxide in the atmosphere [about 0.03% by vol.]
  • It also occurs as hydrocarbons in natural gas & petroleum.
  • In the solid state in wood [cellulose].
  • In plants & animals as carbohydrates & in minerals as limestone – CaCO3

Question: 3. Define the term ‘allotropy’. Give a reason why carbon exhibits allotropy.

Answer: Allotropy — It is the existence of an element in

  • more than one physical form
  • having different physical properties
  • but the same graded chemical properties.

It is the result of difference in atomic arrangement in the crystal structure of the element. Hence they differ in physical properties but are forms of the same element carbon, and hence have similar chemical properties.

Question: 4. Name two crystalline and four amorphous allotropes of carbon.

Answer: Crystalline allotropes of carbon —

  1. Diamond
  2. Graphite

Amorphous allotropes of carbon —

  1. Coal
  2. Coke
  3. Lampblack
  4. Wood charcoal

Question: 5. Compare the structure of the crystal of diamond & graphite with special reference to the reason for diamond being the hardest natural substance while graphite one of the softest. Compare the electrical & thermal conductivity of the two crystalline allotropes of carbon.


Property Diamond Graphite
Structure A three dimensional octrahedral eight sided crystal. A two dimensional sheetlike flat layered crystal.
Nature Diamond is hardest natural substance. Hardness is due to the strength and uniformity of the carbon-carbon covalent bonds in stable and rigid crystal lattice. Graphite is a soft substance. Softness is due to parallel layers of C atoms held together by weak Van Der Waals forces which slide over one another.
Electrical conductivity Non-conductor of electricity due to absence of free electrons in the crystal. Good conductor of electricity due to presence of mobile electrons in the crystal.
Thermal conductivity Very poor conductor of heat Good conductor of heat

Question: 6. With reference to the structure of the two crystalline allotropes of carbon, state why diamond is inert or unreactive while graphite is comparably more reactive.

Answer: In diamond, due to the linking of each carbon atom with four neighbouring carbon atoms forming a rigid tetrahedral structure, there are no free or mobile electrons. This makes diamond inert.
Graphite has a more open structure than diamond with one valence electron of each carbon atom remaining free which makes it more reactive than carbon.

Question: 7. State the reasons for

(a) Use of diamond – as an. item of jewellery,
(b) Use of graphite –
(i) as a lubricant for heated machine parts,
(ii) as a lining for crucibles used in manufacture of high grade steel,
(iii) as an electrode in electroplating.

Answer: (a) Diamond has a sparkling brilliance due to high refractive index hence, it is used as the most precious & expensive item of jewelry.

(b) (i) Ordinary lubricating oils gets charred due to high temperature whereas graphite is non-volatile and non-sticky and can withstand high temperatures.

(ii) Graphite can withstand very high temperature as it has a high melting point and is a good conductor of heat. So it is used as a lining for crucibles used in manufacture of high grade steel.

(iii) Graphite is a good conductor of electricity and is relatively inert. Chemically it is almost inactive with acids hence is used as an electrode in electroplating.

Question: 8. State in brief the transformation of vegetable matter to different types of coal varying in carbon content. State two uses each of-

(a) coal
(b) coke
(c) lampblack or soot.

Answer: Coal is formed by slow bacterial decomposition of vegetable matter. It is formed under the influence of heat, pressure & limited air, over millions of years. The different stages of transformation of vegetable matter results in a residue rich in varying amounts of carbon, hence giving different types of coal

  • Peat [60% C]
  • Lignite [65% C]
  • Bituminous [85% C]
  • Anthracite [90% C ]

(a) Uses of coal —

  1. Mainly as a cheap fuel.
  2. Manufacture of coke, coal gas and synthetic petrol.

(b) Uses of coke —

  1. As a fuel.
  2. As a reducing agent in the iron & steel production.

(c) Uses of lampblack or soot —

  1. For making printers ink, black shoe polish, typewriter ribbons & black paints.
  2. As a filler in rubber tyres.

Question: 9. ‘Wood charcoal – an amorphous allotrope of carbon reduces heated metallic oxides to metals’. Give a balanced equation to support the statement.

Answer: ZnO    +    C    ⟶     Zn   +   CO

Question: 10. Carbon dioxide occurs both in the free state and in the combined state.
State three methods how carbon dioxide is added to the atmosphere.

Answer: Carbon dioxide is added to the atmosphere by:

  1. Respiration in living organisms.
  2. Burning of carbon compounds – e.g. wood, petroleum.
  3. Decay & decomposition of organic matter – e.g. animals, plants.

Question: 11. In the laboratory preparation of carbon dioxide by action of a dilute acid on a metallic carbonate give –

(a) A balanced equation for the preparation
(b) A reason for
(i) use of a washer bottle containing cone. H2SO4 in the preparation
(ii) Not collecting the prepared gas over water
(iii) Not using dilute sulphuric acid as a reactant in the preparation.

Answer: (a) CaCO3 + 2HCl [dil.] ⟶ CaCl2 + H2O + CO2

(b) (i) The evolved carbon dioxide is passed through the washer bottles containing conc. H2SO4, to absorb moisture.

(ii) Carbon dioxide is fairly soluble in water, hence, it is not collected over water,

(iii) Dilute sulphuric acid reacts with calcium carbonate forming a coating of insoluble calcium sulphate on the marble chips thereby the reaction slowly comes to a stop.
CaCO3 + H2SO4 [dil.] ⟶ CaSO4 [insoluble] + H2O + CO2

Question: 12. How would you prove experimentally that

(a) Carbon dioxide does not support combustion
(b) Is slightly acidic in nature.

Answer: (a) Insert a burning candle inside a jar containing carbon dioxide gas. The burning candle is extinguised. It is concluded that carbon dioxide does not support combustion.

(b) Insert a moist blue litmus paper in a jar containing carbon dioxide gas. The paper turns pink or scarlet. It is concluded that carbon dioxide is slightly acidic in nature.

Question: 13. Starting from carbon dioxide how would you obtain

(a) A weak acid
(b) A fertilizer
(c) A highly poisonous gas
(d) Black particles of carbon.
[Give balanced equations for the same] 

Answer: (a) CO2 dissolves in water under pressure to give a weak acid called carbonic acid [H2CO3].

CO2 + H2O ⟶ H2CO3

(b) CO2 reacts with ammonia gas at elevated temperatures & pressures forming Urea [(NH2)2CO], an important nitrogenous fertilizer.

2NH3 + CO2 ⟶ (NH2)2CO + H2O

(c) CO2 when passed over heated coke [carbon] is reduced to Carbon monoxide [CO] which is a highly poisonous gas.

CO2 + C ⟶ 2CO

(d) Burning magnesium burns in CO2 producing Magnesium oxide [MgO] & black particles of carbon [C].

2Mg + CO2 ⟶ 2MgO + C

Question: 14. State how you would convert carbon dioxide to a metallic carbonate using a basic oxide e.g. sodium oxide. [Give a balanced equation]

Answer: Basic oxides such as Na2O & MgO react with CO2 to give metal carbonates such as Na2CO3 & MgCO3 respectively

Na2O + CO2 ⟶ Na2CO3

Question: 15. ‘When carbon dioxide is bubbled into lime water, the lime water turns milky and when bubbled in excess the milkiness disappears’. Give balanced equations to support the statement.

Answer: When carbon dioxide is bubbled into lime water, the lime water turns milky due to the formation of insoluble calcium carbonate.

Ca(OH)2 + CO2 ⟶ CaCO3 ↓ + H2O

When CO2 is bubbled in excess the milkiness disappears due to the formation of soluble calcium bicarbonate [Ca(HCO3)2]

CaCO3 + H2O + CO2 ⟶ Ca(HCO3)2

Question: 16. Explain the term ‘dry ice’. State its application. Give three reasons why carbon dioxide finds application in fire extinguishers.

Answer: Liquid carbon dioxide on sudden evaporation results in freezing and formation of solid carbon dioxide which is called ‘dry ice’.

It is used as a refrigerant for preservation of foods.

Three reasons for using carbon dioxide in fire extinguishers:

  1. It is non-combustible.
  2. It is non-supporter of combustion.
  3. It is heavier than air, hence cuts out the fire.

Question: 17. Using a magnesium ribbon, how would you prove that a given gas jar contains carbon dioxide.

Answer: On burning magnesium ribbon in a jar of carbon dioxide, the black particles of carbon are deposited on the walls of the jar. Hence, the presence of carbon dioxide can be detected.

CO2 + 2Mg ⟶ 2MgO + C

Question: 18. State the function of cone, sulphuric acid in the laboratory preparation of carbon monoxide from oxalic acid.

Answer: Conc. sulphuric acid acts as a dehydrating agent & removes a molecule of water from oxalic acid to produce carbon monoxide and carbon dioxide. The reaction is given below:

Conc. sulphuric acid

Question: 19. Give reasons why carbon monoxide is considered a highly poisonous gas. State why it is dangerous.

1. To sleep in a closed room with a fuel burning
2. To be in the vicinity of smokers.

Answer: Carbon monoxide combines with the haemoglobin in the red cells forming a stable compound carboxyl-haemoglobin which prevents the haemoglobin from taking up oxygen. A person thus dies due to lack of oxygen resulting in asphyxia which is a condition caused by lack of oxygen resulting in suffocation or death.

(i) It is dangerous to sleep in a closed room with a coal fire burning since carbon burns in a limited supply of air forming carbon monoxide, which is fatal to life.

(ii) As fumes of burning tobacco contains traces of carbon monoxide, which is a poisonous gas, hence it it dangerous to be in the vicinity of smokers.

Question: 20. Convert carbon monoxide to carbon dioxide using two different methods.

Answer: (i) Carbon monoxide burns in oxygen forming carbon dioxide.

2CO + O2 ⟶ 2CO2

(ii) Carbon monoxide reduces heated metallic oxides to metals and evolve carbon dioxide gas.

ZnO + CO ⟶ Zn + CO2

Question: 21. State how carbon monoxide finds application in

1. The metallurgy of iron
2. Preparation of an alcohol.
[Give balanced equations for the same]

Answer: (i) Carbon monoxide is used in the extraction of metals from their ores — Reduces heated metallic oxides e.g. iron [III] oxide to iron.

Fe2O3 + 3CO ⟶ 2Fe + 3CO2

(ii) Two volumes of H2 reacts with one volume of carbon monoxide to form methyl alcohol.

CO + 2H2 ⟶ CH3OH [methyl alcohol]

– : End of Carbon & Its Compound Class-8 Dalal Solutions :–

Return to –  Dalal Simplified Chemistry for ICSE Class-8 Solutions


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