NTEXT QUESTIONS 28.1
1. What is the valency of carbon?
Answer: The valency of carbon is 4.
2. What is the nature of bonds formed by carbon?
Answer: The bonds formed by carbon are covalent bonds.
3. Why carbon forms a large number of compounds?
Answer: Carbon forms a large number of compounds because it has the property of catenation, which allows it to form long chains and rings with other carbon atoms. It also shows isomerism, where compounds have the same formula but different structures, and forms compounds with various functional groups, increasing the variety of carbon compounds.
4. Name the branch of chemistry which is devoted to the study of carbon compounds.
Answer: The branch of chemistry devoted to the study of carbon compounds is organic Chemistry.
5. How many electrons are needed by a carbon atom to complete its octet?
Answer: A carbon atom needs 4 electrons to complete its octet.
INTEXT QUESTIONS 28.2
1. Which allotropic form of carbon has been discovered few years back?
Answer: The allotropic form of carbon discovered a few years back is fullerene.
2. Each carbon atom is linked to how many carbon atoms in
(i) Diamond
(ii) Graphite
Answer: (i) In diamond, each carbon atom is linked to 4 other carbon atoms.
(ii) In graphite, each carbon atom is linked to 3 other carbon atoms.
3. Why diamond has high melting point?
Answer: Diamond has a high melting point because a large amount of heat energy is required to break its strong three-dimensional network of covalent bonds.
4. Is diamond a conductor of electricity? Give reason for your answer.
Answer: No, diamond is not a conductor of electricity because it has no free electrons to carry electric current. All its valence electrons are used in forming strong covalent bonds.
5. Why is graphite a good lubricant?
Answer: Graphite is a good lubricant because the weak forces between its layers of carbon atoms allow the layers to slide over each other easily.
6. Give two uses of graphite.
Answer: Two uses of graphite are:
(i) As electrodes.
(ii) As a lubricant.
7. What kind of structure is possessed by fullerenes?
Answer: Fullerenes have a closed structure similar to a football.
8. Name the three microcrystalline forms of carbon and give their use.
Answer: The three microcrystalline forms of carbon and one use of each are:
(i) Charcoal is used for absorbing coloured impurities.
(ii) Coke is used as a reducing agent in metallurgy.
(iii) Carbon black is used as a pigment in inks or in automobile tyres.
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