Carbon and its Compounds: CBSE Class 10 Chemistry practice questions
Practise 50 questions on Carbon and its Compounds, free, with an explanation for each answer.
Sample questions
A carbon atom has 4 valence electrons. To get a noble gas configuration, it could gain four electrons or lose four electrons. Why does carbon not do this?
- Carbon already has a completely filled outer shell, so it never forms bonds
- Carbon has six valence electrons, so it only needs to gain two, which is easy
- Gaining or losing four electrons is very hard, so carbon shares electrons
- Electrons can never be shared between atoms in a molecule
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C. Gaining or losing four electrons is very hard, so carbon shares electrons
Carbon (atomic number 6, configuration 2, 4) would have to gain four electrons, but a nucleus of 6 protons cannot easily hold 10 electrons; or it would have to lose four electrons, which needs a huge amount of energy and leaves just 2 electrons round 6 protons. So carbon shares its valence electrons with other atoms and forms covalent bonds. Carbon has 4 (not 6) valence electrons, its outer shell is not full, and electron sharing is exactly how many molecules form.
Ethane has the molecular formula . How many covalent bonds does it have?
- 6
- 7
- 8
- 9
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B. 7
In the structure of ethane there are six C-H single bonds (three on each carbon) and one C-C single bond, so 7 bonds in all. The common trap is to count only the six C-H bonds and forget the C-C bond (answer 6). Counts of 8 or 9 over-count the bonds.
Pentane is . How many structural isomers can be drawn for it? (Count straight-chain pentane also.)
- 2
- 3
- 4
- 5
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B. 3
Pentane has three structural isomers: straight-chain pentane, 2-methylbutane (a four-carbon chain with one methyl branch) and 2,2-dimethylpropane (a central carbon with four other carbons). The trap is counting the same skeleton drawn bent in a different way as a new isomer.
Topics covered
- Bonding in carbon: the covalent bond
- Properties of covalent compounds
- Allotropes of carbon
- Versatile nature of carbon
- Saturated and unsaturated compounds
- Homologous series
- Chains, branches and rings
- Functional groups
- Nomenclature of carbon compounds
- Combustion
- Oxidation
- Addition reaction
- Substitution reaction
- Ethanol
- Ethanoic acid
- Reactions of ethanol and ethanoic acid
- Soaps and detergents