Carbon and Its Compounds ICSE Class-8th Concise Selina Chemistry Solutions

Carbon and Its Compounds ICSE Class-8th Concise Selina Chemistry Solutions Chapter-9. We Provide Step by Step Answer of Objective, True False , Fill in the blanks, Match the following , Short / Long Answer Type of Exercise-9 Carbon and Its Compounds. Visit official Website CISCE for detail information about ICSE Board Class-8.


Carbon and Its Compounds ICSE Class-8th Concise Selina Chemistry Solutions


Exercise – I


Question 1.

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Fill in the blanks.

(a) Carbon is present in both living and non-living things.
(b) The tendency of an element to exist in two or more forms but in the same physical state is called Allotropy.
(c) Crystalline and non- crystalline are the two major crystalline allotropes of carbon.
(d) Diamond is the hardest substance that occurs naturally.
(e) The name ‘carbon’ is derived from the Latin word carbo.

Question 2.


Choose the correct alternative.

(a) In combined state, carbon occurs as
(i) coal
(ii) diamond
(iii) graphite
(iv) petroleum

Answer:

petroleum

(b) A crystalline form of carbon is
(i) lampblack
(ii) gas carbon
(iii) sugar
(iv) fullerene

Answer:

sugar

(c) Graphite is not found in
(i) Bihar
(ii) Maharashtra
(iii) Orissa

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Answer:

Maharashtra

(d) Diamond is used for
(i) making the electrodes of electric furnaces.
(ii) making crucible for melting metals.
(iii) cutting and drilling rocks and glass.
(iv) making carbon brushes for electric motors.

Answer:

cutting and drilling rocks and glass

(e) Carbon forms innumerable compounds because
(i) it has four electrons in its outermost shell.
(ii) it behaves as a metal as well as a non- metal.
(iii) carbon atoms can form long chains.

(iv) it combines with other elements to form covalent compounds.

Answer:

carbon atoms can form long chains.

 

Question 3.Carbon and Its Compounds ICSE


Write ‘true’ or ‘false’ against the following statements.

(a) Carbon constitues 0.03% of the earth’s crust. – True
(b) Graphite is the purest form of carbon. – False
(c) Coloured diamonds are costlier than colourless and transparent diamonds. – False
(d) Graphite has layers of hexagonal carbon bondings. – True
(e) Diamond is insoluble in all solvents. – True.

 

Question 4.

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Define the following terms:

(a) Allotropy (b) Carat
(c) Crystal (d) Catenation
Answer:
(a) Allotropy: Allotropy is defined as the phenomenon due to which an element exists in two or more forms in the same physical state with identical chemical properties but with different physical properties.

(b) Carat – The weight of diamond is expressed in carats [ 1 carat = 0.2 g]

(c) Crystal – A crystal is a homogeneous solid which particles (atoms, molecules or ions) are arranged in difinite pattern due to which they have definite geometrical shape with plane surfaces e.g. sugar and sodium chloride.

(d) Catenation – The large number of organic compounds is due to the ability of carbon atom to form long chains with other carbon atoms through the sharing of electrons. This unique property of carbon is known as catenation.

 

Question 5.


State the terms:

(a) Substances whose atoms or molecules are arranged in a definite pattern. – Crystals.
(b) Different forms of an element found in the same physical state. – Allotropy.
(c) The property by which atoms of an element link together to form long chain or ring compounds. – Catenation

Question 6.Carbon and Its Compounds ICSE


Name the following:

(a) The hardest naturally occurring substance. – Diamond.
(b) A greyish black non- metal that is a good conductor of electricity. – Graphite.
(c) The third crystalline form of carbon. – Fullerenes.

 

Question 7.


Answer the following questions:

(a) Why is graphite a good conductor of electricity but not diamond?
(b) Why is diamond very hard?
(c) What are fullerenes? Name the most common fullerenes.
(d) What impurity is present in black diamond?
(e) Explain the softness of graphite with reference to its structure.
Answer:
(a) In a graphite molecule, one valence electron of each carbon atom remains free, Thus making graphite a good conductor of electricity. Whereas in diamond, they have no free mobile electron. Thats why diamond are bad conductor electricity.

(b) A diamond is a giant molecule. The number of valence electrons in carbon atom is four. As such each carbon atom is linked with four neighboring carbon atoms. Thus forming a rigid tetrahedral structure. It is the strong bonding’that makes diamond the hardest substance.

(c) Fullerenes: Fullerenes are the third crystalline form of carbon.
Though they were discovered only recently. They have.been found to exist in interstellar dust as well as in the geological formations of the earth.
Common fullerenes are C – 32, C – 50, C – 70 and C – 76

(d) Black diamonds have copper oxide present in them as impurity.

(e) In a graphite molecule of each carbon atoms is linked with three neighboring carbon atoms. Thus forming a hexagonal arrangement of atoms. These hexagonal grouping of carbon atoms are arranged as layers or sheets piled one the top of other. The layers are held together by weak forces such that they can slide over one another. That is why graphite is soft.

Question 8.


Give two uses of (a) graphite (b) diamond.
Answer:

(a) Uses of graphite:

  1. For making the electrodes of electric furnaces.
  2. For making crucibles for melting metals due to its high melting points.

(b) Uses of Diamond:

  1. Diamond is used in jewellery as a gem
  2. It is used for cutting and drilling rocks, glass,

Question 9.


Write three differences between graphite and diamond.
Answer:
Difference between diamond and graphite.

Diamond

  1. Pure diamond is colourless and transparent.
  2. It is the hardest naturally occurring substance.
  3. It has high density i.e. 3.5 g/cm3
  4. It is bad conduct of electricity.
  5. It bums in air at 900°C to form carbon dioxide.

Graphite

  1. Graphite is greyish black opaque and shiny.
  2. It is soft and greasy to touch.
  3. It has low density i.e. 2.39 g / cm3
  4. It is good conductor of electricity.
  5. It bums in air at 700° C to form carbon dioxide.

Exercise – II Carbon and Its Compounds ICSE

Question 1.

Fill in the blanks:

(a) Charcoal is formed when charcoal is burnt in a limited supply of air.

(b) Coal is a amorphous form of carbon.
(c) Peat is the most inferior form of coal.
(d) Wood charcoal is a bad conductor of heat and electricity.
(e) lampblack is used in making black shoe polish.

Question 2.


Choose the correct alternative

(a) Anthracite is
(i) an inferior type of coal
(ii) a superior type of coal
(iii) a cheapest form of coal
(iv) none of above

Answer: 

a superior type of coal

(b) Destructive distillation of coal yields
(i) coal tar
(ii) coal gas
(iii) coke
(iv) a superior type of coal

Answer: 

a superior type of coal

(c) Lamp black is
(i) an amorphous form of carbon
(ii) a crystalline form of carbon
(iii) a pure form of carbon
(iv) a cluster of carbon atoms

Answer: 

an amorphous form of carbon

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