Chapter 13 Carbon: An Important Element Solutions

Maharashtra State Board Class 9 Science Solutions Chapter 13 Carbon: An Important Element

Class 9 Science Chapter 13 Carbon: An Important Element Textbook Questions and Answers

1. Select the proper option and complete the statements
(single, all, double, ionic, carbon, give and take, hydrogen, multiple, share, most, covalent)

a. A carbon atom forms a ….……………. bond with other atoms. In this bond the two atoms ….electrons.
Answer:
covalent, share

b. All the carbon bonds in a saturated hydrocarbon ….……………. electrons.
Answer:
share

c. At least one carbon bond in an unsaturated hydrocarbon is ….…………….
Answer:
multiple

d. ….……………. is the essential element in all the organic compounds.
Answer:
Carbon

e. The element hydrogen is present in ….. organic compound.
Answer:
all

2. Answer the following questions

a. Why are carbon and its compounds used as fuels?

Answer:
(i) The name ‘carbon’ is derived from Latin word ‘carbo’meaning coal. In the earth’s crust, carbon is present to an extent of approximately 0.27% in the form of carbonate, coal and petroleum. One of the non-crystalline and amorphous form of carbon is coal. Coal is a fossil fuel.

(ii) Peat, lignite, bituminous and anthracite are the four types of coal in the increasing order of their carbon content and heat produced respectively. Charcoal and coke are the other amorphous forms of carbon used as fuel.

(iii) Compounds of carbon such as hydrocarbons consist of carbon and hydrogen and they are easily combustible. For example, methane (CH₄) which occurs in natural gas is highly inflammable. It bums by reacting with oxygen to give a bluish flame. In this reaction, 213 Kcal/mol of heat is given out. Methane bums completely.

Chemical reaction:
CH₄+ 2O₂→ CO₂+ 2H₂O + Heat

(iv) Thus when hydrocarbons are burnt in air, large amount of heat is evolved with formation of carbon dioxide (CO₂) and water (H₂O). Due to evolution of heat on combustion, carbon and its compounds are used as fuels.

b. In which compound forms does carbon occur?
Answer:
Carbon in its combined state exists as various compounds such as:

c. Write the uses of the diamond.
Answer:
Uses of diamonds are:

3. Explain the difference:

a. Diamond and graphite.

Answer:

b. Crystalline and non-crystalline forms of carbon.
Answer:

4. Write scientific reasons

a. Graphite is a conductor of electricity.
Answer:

b. Graphite is not used in ornaments.
Answer:

c. Limewater turns milky when CO₂is passed through it.
Answer:

d. Biogas is an eco-friendly fuel.
Answer:

5. Explain the following.

a. Diamond, graphite and fullerenes are crystalline forms of carbon.
Answer:

b. Methane is called marsh gas.
Answer:

c. Petrol, diesel, coal are fossil fuels.
Answer:
(i) A fossil fuel is a fuel formed by natural processes, such as anaerobic decomposition of buried dead organisms. Fossil fuels contain high percentage of carbon. The word carbon is derived from the Latin word ‘Carbo’ meaning coal.

(ii) Coal is formed from the remains of trees and other vegetation. Approximately 350 million years ago, these remains were trapped on the bottom of swamps, accumulating layer after layer and creating a dense material called peat. As this peat was buried under more and more ground, the high temperature and pressure transformed it into coal.

(iii) Petrol and diesel are obtained from mineral oil. Mineral oil also called as crude oil or petroleum oil is formed from the remains of plants and animals that lived in the seas millions of years ago. This plant and animal matter has been drawn down and subjected to extremes of temperature and pressure over millions of years ago.

(iv) Mineral oil is commonly formed in rocks under the sea bed. The word petroleum is derived from Latin word ‘Rock oil’. Petrol and Diesel are obtained from mineral oil by the process called as fractional distillation.
Thus petrol, diesel and coal are fossil fuels.

d. Uses of various allotropes of carbon.

e. Use of CO₂in fire extinguisher.
Answer:

f. Practical uses of CO₂.
Answer:
Practical uses of CO₂are:

6. Write two physical properties each.

a. Diamond
Answer:
Properties of diamond are:

b. Charcoal
Answer:

c. Fullerene
Answer:
Properties of fullerenes are:

7. Complete the following Chemical reactions.

1. ………………..+………………..→ CO + 2H₂O + Heat
2. ………………..+………………..→ HCl + Cl + HCl
3. 2 NaOH + CO₂→………………..+………………..
Answer:

8. Write answers to the following in detail.

a. What are the different types of coal? What are their uses?
Answer:
Coal is a fossil fuel. It contains carbon, hydrogen and oxygen. It also contains nitrogen, phosphorus and sulphur. It occurs in the solid state. It is of four types.

Uses of coal:

b. How will you prove experimentally that graphite is good conductor of electricity?
Answer:
Apparatus required: Lead pendi, electrical wires, battery/cell, small bulb, etc.

Step-I: Remove the lead from a pencil and assemble the apparatus as shown in the diagram.

Step-II:

c. Explain the properties of carbon.
Answer:
Allotropic nature of Carbon: Some elements occur in nature in more than one form. The chemical properties of these different forms are the same but their physical properties are different. This property of elements is called allotropy. Carbon shows the property of allotropy.

Carbon allotropes are of two types:
(A) Crystalline forms:
Carbon has three crystalline allotropes: Diamond, Graphite and Fullerene. Properties of crystalline forms of carbon are as follows:

(B) Amorphous forms or non-crystalline forms: Coal, charcoal, coke are the non-crystalline forms of carbon.
Properties of non-crystalline forms of carbon are as follows:

d. Classify carbon.
Answer:
Carbon is classified as follows:

9. How will you verify the properties of carbon dioxide?
Answer:
Properties of carbon dioxide can be verified in the following ways:

Class 9 Science Chapter 13 Carbon: An Important Element Intext Questions and Answers

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Class 9 Science Chapter 13 Carbon: An Important Element Additional Important Questions and Answers

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