Living Science Chemistry Class 8 ICSE Solutions Chapter 9 Carbon and Its Compounds

ICSE Living Science Chemistry for Class 8 Solutions Chapter 9 Carbon and Its Compounds

Check Your Progress (Page 117)

Answer these questions.
Question 1.
Name the three crystalline allotropes of carbon.
Answer:
Diamond, graphite and fiillerene are the three crystalline allotropes of carbon.

Question 2.
Which is the purest form of carbon?
Answer:
Diamond is the purest form of carbon.

Question 3.
Which type of bond joins the carbon atoms in a diamond?
Answer:
Each carbon atom in diamond is joined to four other carbon atoms by covalent bonds.

Question 4.
Name an allotrope of carbon that is a good conductor of electricity.
Answer:
Graphite is a good conductor of electricity.

Question 5.
How many carbon atoms can fullerenes have?
Answer:
A molecule of fullerenes can have about 30 to 900 atoms of carbon.

A. Tick the most appropriate answer

Question 1.
Graphite is used as a lubricant because it is
a. a good conductor of heat
b. a good conductor of electricity.
c. soft and slippery.
d. soluble in organic solvents.
Answer:
a. a good conductor of heat.

Question 2.
An example of an amorphous form of carbon –
a. diamond.
b. graphite
c. fullerene.
d. wood charcoal.
Answer:
d. wood charcoal.

Question 3.
A form of carbon that is a good conductor of –
a. diamond.
b. graphite.
c. wood charcoal.
d. coke.
Answer:
a. diamond.

Question 4.
Buckyball is found in –
a. dust
b. rocks.
c. soot
d. none of these
Answer:
c. soot

Question 5.
Lampblack is used in making –
a. shoe polish.
b. black paint
c. ink.
d. all of these
Answer:
d. all of these

Question 6.
Calcium carbonate on heating produces –
a. Ca.
b. CaO₂
c. Ca₂O
d. CO₂
Answer:
d. CO₂

Question 7.
Carbon monoxide reduces Fe₂O₃ to –
a. Fe.
b. Fe₂O
c. FeO₂
d. none of these
Answer:
a. Fe.

B. Fill in the blanks

Question 1.
…………. , …………. and ………… are the three crystalline forms of carbon.
Answer:
Diamond, graphite and fullerene are the three crystalline forms of carbon.

Question 2.
Some diamonds have different colours due to ………….. in them.
Answer:
Some diamonds have different colours due to impurities in them.

Question 3.
The diamond crystal is a regular ……………. having one carbon at each of its ………… corners and one carbon
lying at its …………..
Answer:
The diamond crystal is a regular tetrahedron having one carbon at each of its four comers and one carbon lying at its centre.

Question 4.
The molecules of the first fullerene are composed of …………… carbon atoms.
Answer:
The molecules of the first fullerene are composed of 60 carbon atoms.

Question 5.
……………. is the purest form of amorphous carbon.
Answer:
Gas carbon is the purest form of amorphous carbon.

Question 6.
……………. is used in making shoe polish and printer’s ink.
Answer:
Lamp black is used in making shoe polish and printer’s ink.

Question 7.
Gas carbon and graphite are ……………. conductors of electricity.
Answer:
Gas carbon and graphite are good conductors of electricity.

Question 8.
…………. is produced when metal carbonates or bicarbonates are treated with dilute acids.
Answer:
Carbon dioxide is produced when metal carbonates or bicarbonates are treated with dilute acids.

C. Write true or false. Correct the false statements

Question 1.
Synthetic diamonds are used in cutting and grinding tools.
Answer:
True

Question 2.
Diamond is a good conductor of heat and electricity.
Answer:
False; Diamond is a good conductor of heat.

Question 3.
Diamond is the purest form of carbon.
Answer:
True

Question 4.
Graphite is used as a lubricant in machinery.
Answer:
True

Question 5. Carbon dioxide is collected by the downward displacement of air.
Answer:
True

Question 6.
Carbon dioxide is acidic in nature.
Answer:
True

Question 7.
Carbon monoxide combines with the haemoglobin in the red blood cells of our body to form carboxyhaemoglobin.
Answer:
True

D. Match the columns

1. Adsorption – a. used for making electrodes
2. Reducing agent – b. CO + H₂
3. Gas carbon – c. CO + N₂
4. Fullerene – d. wood charcoal
5. Ivory black – e. carbon monoxide
6. Water gas – f. used as a black pigment
7. Producer gas – g. electronic devices
Answer:
1. Adsorption – d. wood charcoal
2. Reducing agent – e. carbon monoxide
3. Gas carbon – a. used for making electrodes
4. Fullerene – g- electronic devices
5. Ivory black – f. used as a black pigment
6. Water gasn – b. CO + H₂
7. Producer gas – c. CO + N₂

E. Name the following

Question 1.
Existence of an element in more than one form in the same physical state
Answer;
Allotropy

Question 2.
The bond between carbon atoms in graphite
Answer:
Covalent

Question 3.
The process of breakdown of organic substances on heating strongly in the absence of air
Answer:
Destructive distillation

Question 4.
The property of attracting gases, liquids or solids to its surface by a solid
Answer:
Adsorption

Question 5.
A mixture of sodium bicarbonate and tartaric acid
Answer;
Baking powder

Question 6.
A condition that can cause death by breathing in carbon monoxide
Answer:
Asphyxia

F. Write balanced chemical equations of the following

Question 1.
Dehydrating cane sugar with concentrated sulphuric acid
Answer:

Question 2.
Passing carbon dioxide through lime water
Answer:
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Question 3.
Sodium bicarbonate reacting with dil. sulphuric acid
Answer:
2NaHCO₃+ H₂SO₄ → Na₂SO₄ + 2H₂O + 2CO₂

Question 4.
Carbon dioxide reacting with gaseous ammonia
Answer:
2NH₃ + CO₂ → NH₂CONH₂ + H₂O

Question 5.
Carbon monoxide reacting with iron (III) oxide
Answer:
Fe₂O₃ + 3CO > 2Fe + 3CO₂

G Answer the following in short

Question 1.
What is allotropy ?
Answer:
The existence of an element in two or more forms in the same physical state is known as allotropy. Examples : Carbon, sulphur and phosphorous show allotropy.

Question 2.
Name the crystalline allotropes of carbon.
Answer:
The crystalline allotropes of carbon are diamond, graphite and fullerenes.

Question 3.
How are synthetic diamonds prepared ?
Answer:
Synthetic or artificial diamonds can be prepared by compressing carbon under extremely high pressure and temperature.

Question 4.
What is the electrical and thermal conductivity of graphite?
Answer:
Graphite is a good conductor of heat and electricity.

Question 5.
What is fullerene ?
Answer:
Fullerene is the most recently discovered crystalline allotropic form of carbon. It looks like a soccer ball and consists of 30 to 900 atoms of carbon in molecule.

Question 6.
What do you understand by destructive distillation ?
Answer:
The process of the breakdown of organic substances such as coal and wood on heating them strongly in the absence of air is known as destructive distillation.

Question 7.
What is adsorption ?
Answer:
The property of a solid to attract gases, liquids or solids to its surface is called adsorption.

Question 8.
Why is wood charcoal a better fuel than wood ?
Answer:
Wood charcoal is a better fuel than wood because it bums better and causes less air pollution.

Question 9.
How is bone charcoal prepared ?
Answer:
Bone charcoal is obtained by heating bones in the presence of a limited supply of air.

Question 10.
How is coke obtained ?
Answer:
Coke is obtained as a residue during the destructive distillation of coal.The gases and other substances present in coal are given off on heating.

H. Answer the following in detail

Question 1.
Explain the structure of diamond.
Answer:
Each carbon atom in diamond is joined to four other carbon atoms by covalent bonds. The diamond crystal is a regular tetrahedron having one carbon atom at each of its four comer and one carbon atom lying at its centre. Each carbon at the comer is further attached to three more carbon atoms and so on. As a result, a diamond crystal appears to be a closely packed three- dimensional rigid structure.

Question 2.
Explain the arrangement of carbon atoms in graphite.
Answer:
Graphite has a layered structure. It is made up of flat planar layer of carbon atoms. Each layer contains hexagonal rings consisting of six carbon atoms. In graphite, each carbon atom is covalently linked to three carbon atoms, rather than four (valency of carbon is 4), leaving the fourth valence electron of carbon atom free. The free-electron accounts for the electrical conductivity of graphite. Graphite contains layers of carbon atoms held together by weak forces of attraction. The layers, therefore, slide over each other easily, making graphite soft and slippery.

Question 3.
Differentiate between diamond and graphite.
Answer:

Question 4.
Explain the structure of Buckminsterfullerene.
Answer:
A molecule of fullerenes can have about 30 to 900 atoms of carbon, for example, C₃₂, C₅₀, Go and so on. Molecules of fullerenes form either a closed cage or a cylinder in shape. The first fullerence was prepared (artificially) in 1985 by R. Buckminster Fuller. Hence, it was named Buckminsterfullerene after him. It’s molecules are composed of 60 carbon atoms (C₆₀). The C₆₀ arrangements of carbon atoms look like the dome structures. The shape of buckminsterfullerene or buckyball looks like a soccer ball and has 12 pentagonal and 20 hexagonal faces.

Question 5.
Write four uses of coal.
Answer:
Uses of coal.

• It is used as a fuel.
• It is used in the production of coke.
• It is used in the generation of electricity.
• It is used to manufacture numerous compounds such as dyes, waxes and oils.
• It is also used to produce liquid and gaseous fossil fuels.

Question 6.
Write four uses of carbon dioxide.
Answer:

• Uses of carbon dioxide In carbonated drinks: As it is easily soluble in water under pressure, carbon dioxide is used in the manufacture of carbonated drinks.
• As a refrigerant for preservation of foods: Dry ice (solid carbon dioxide) is extremely cold. It sublimes and is non- poisonous. Hence, it is used as a refrigerant for preserving food items such as vegetables, fruits and meat.
• In the manufacture of urea(fertilizer): Carbon dioxide is reacted with gaseous ammonia to manufacture urea, an important nitrogenous fertilizer.
• In the manufacture of chemicals: Carbon dioxide is used in the manufacture of chemicals such as washing soda (sodium carbonate) and baking soda (sodium bicarbonate).

Question 7.
Describe the poisonous nature of carbon monoxide.
Answer:
Carbon monoxide is a highly poisonous gas. By breathing in it, it combines with the haemoglobin in the red blood cells of our body to form a stable compound called carboxyhaemoglobin, which lowers the oxygen-carrying capacity of red blood cells. This results in death due to suffocation, which is known as asphyxia.

I. Draw diagrams of the following

Question 1.
Structure of diamond
Answer:
Each carbon atom in diamond is joined to four other carbon atoms by covalent bonds. The diamond crystal is a regular tetrahedron having one carbon atom at each of its four comer and one carbon atom lying at its centre. Each carbon at the comer is further attached to three more carbon atoms and so on. As a result, a diamond crystal appears to be a closely packed three- dimensional rigid structure.

Question 2.
Destructive distillation of dry wood
Answer:
Destructive distillation of dry wood

Question 3.
Preparation of carbon dioxide in the laboratory
Answer:
Preparation of carbon dioxide in the laboratory

Think And Answer

Question 1.
Diamonds have extraordinary brilliance. Explain.
Answer:
When light enters a diamond crystal, it undergoes multiple internal reflections, which makes the diamond sparkle.

Question 2.
Graphite is soft and slippery and a good conductor of electricity. Why?
Answer:
Graphite contains layers of carbon atoms held together by weak forces of attraction. Therefore, the layers slide over each other easily, making graphite soft and slippery. For this reason, graphite is used as a lubricant.

Question 3.
Coke is used in the extraction of metals such as zinc and iron from their ores. Why?
Answer:
Coke is a good reducing agent. It is therefore used in the extraction of metals such as zinc and iron from their ores.

Question 4.
Carbon monoxide causes asphyxia. Why?
Answer:
By breathing in it, it combines with the haemoglobin in the red blood cells of our body to form a stable compound called carboxyhaemoglobin, which lowers the oxygen-carrying capacity of red blood cells. This results in death due to suffocation, which is known as asphyxia.

Living Science Chemistry Class 8 ICSE Solutions