Carbon Unit 1

Question 1

What do you understand by the term Organogens? Name the four elements that constitue as organogens.

Answer 1

Elements hydrogen, oxygen, carbon and nitrogen are called organogens, which means the substances from which organic life, i.e., plants and animals, started.

Question 2

Name two substances in which carbon occurs in free state.

Answer 2

Diamond, Graphite

Question 3

Name two substances in which carbon occurs in combined solid state.

Answer 3

Lime, Marble

Question 4

Name two substances in which carbon occurs in combined liquid state.

Answer 4

Vegetable Oil, Petrol

Question 5

Name two substances in which carbon occurs in combined gaseous state.

Answer 5

natural gas, coal gas

Question 6

Define Allotropy.

Answer 6

The phenomenon due to which an element exhibits different physical forms, which have same chemical properties is called allotropes.

Question 7

Define allotropic forms.

Answer 7

Various physical forms of an element, having different physical properties, but same chemical properties are called allotropes or allotropic forms.

Question 8

Name the crystalline forms of carbon.

Answer 8

Diamond, Graphite, Fullerenes

Question 9

Name the amorphous forms of carbon.

Answer 9

Wood charcoal, lamp black, coke, gas carbon

Question 10

How are diamonds formed in nature?

Answer 10

The earth contains molten magma. Sometimes, carbon present within the earth dissolves in molten magma. When molten magma, containing dissolved carbon, is pushed up towards the surface of the earth, it solidifies.
The iron present in magma, on solidification, expands and exerts a great pressure on carbon. The carbon, in turn, crystallises out in the form of diamond. This fact is supported by discovery of diamonds in shafts of extinct volcanoes.

Question 11

Describe the structure of a diamond molecule.

Answer 11

A diamond crystal has usually eight sides, forming double pyramids. To a regular diamond crystal, each carbon atom is held firmly in place four bonds of neighbouring carbon atoms. Such a configuration forms highly strong bond and hence makes it the hardest naturally occurring
substance.

Question 12

What factors determine the value of a diamond?

Answer 12

The value of a diamond depends upon:

1. Its weight.
2. Freedom from flaws and impurities.

Question 13

State six physical properties of a diamond.

Answer 13

1. It is the hardest naturally occurring solid. Amongst the diamonds, the black diamonds are the hardest.
2. A pure diamond is a (i) colourless, (ii) transparent, and (ii) brittle solid.
3. A pure diamond is transparent to X-rays and the visible light.
4. It is a very poor conductor of heat and electricity.
5. It is insoluble in all solvents.
6. It is stable towards heat. If diamond is heated in vacuum, it does not melt. However, prolonged heating will change it to graphite.

Question 14

State the uses of a black diamond.

Answer 14

(i) For cutting glass as well as diamonds.
(ii) As tips of deep boring drills.
(iii) As bearings in watches.
(iv) As tips of tools for cutting very hard machines
(v) Diamond dust is used for polishing Diamonds
(vi) Diamonds are used as needles for record-players

Question 15

What is graphite?

Answer 15

Graphite is a crystalline form of carbon which occurs in free state. It is one of the pure forms of carbon.

Question 16

Describe the structure of graphite.
OR
Why is graphite a good conductor of electricity?
OR
Why is graphite smooth and slippery to touch?
OR
Why is graphite an excellent lubricant?

Answer 16

In graphite, the atoms are arranged in the form of hexagonal rings in flat planes, such that the rings are stacked on top of each other. Each carbon atom in a hexagonal ring is attached to three other carbon atoms in the same ring. The fourth valence electron remains loose between the rings. These valance electrons are the reason that graphite is a good conductor of heat and electricity. Furthermore, the loose bonds between the rings enable them to slide, hence making graphite smooth, slippery and an excellent lubricant.

Question 17

How is graphite artificially manufactured?

Answer 17

Graphite is manufactured by mixing powdered coke, a little sand and ferric oxide in an electric furnace.

Question 18

State the physical properties of graphite.

Answer 18

1. It is a dark grey solid having a metallic lustre.
2. It has a soft greasy touch. t marks the paper grey.
3. Its density is 2.25 gcm-3
4. It is a good conductor of heat and electricity.
5. It is insoluble in ordinary solvents.

Question 19

State the uses of Graphite.

Answer 19

Check notes

Question 20

What is a fullerene?

Answer 20

Crystalline forms of carbon having 30 to 960 atoms in their molecules are called Fullerenes.

Question 21

How many atoms are present in a buckminsterfullerene? How are these atoms arranged?

Answer 21

In Buckminsterfullerene, each molecule has 60 atoms arranged in hexagons and pentagons.

Question 22

Water has two more physical forms, ice and steam. Why are ice and steam not called allotropes of water?

Answer 22

Check Notes

Question 23

Name two important places of India where diamonds are mined.

Answer 23

Panna, MP; Golconda, Telengana

Question 24

Name two world famous diamonds mined from India.

Answer 24

Kohinoor, Nizam