3 marksShort AnswerSection A

(a) Why are most carbon compounds poor conductors of electricity? (b) Write the name and structure of a saturated compound in which the carbon atoms are arranged in a ring. Give the number of single bonds present in this compound.

Q: (a) Why are most carbon compounds poor conductors of electricity? (b) Write the name and structure of a saturated compound in which the carbon atoms are arranged in a ring. Give the number of single bonds present in this compound.

### (a) Electrical Conductivity of Carbon Compounds Most carbon compounds are poor conductors of electricity because they form **covalent bonds** by sharing electrons. In these compounds, no ions or free charged particles are formed to conduct an electric current. ### (b) Saturated Ring Compound - **Name**: Cyclohexane - **Formula**: $C_6H_{12}$ - **Structure**: ```diagram {"xrange": [25.6, 174.4], "yrange": [35.6, 184.4], "lines": [{"from": [100.0, 50.0], "to": [160.0, 80.0], "label": ""}, {"from": [160.0, 80.0], "to": [160.0, 140.0], "label": ""}, {"from": [160.0, 140.0], "to": [100.0, 170.0], "label": ""}, {"from": [100.0, 170.0], "to": [40.0, 140.0], "label": ""}, {"from": [40.0, 140.0], "to": [40.0, 80.0], "label": ""}, {"from": [40.0, 80.0], "to": [100.0, 50.0], "label": ""}], "points": [{"x": 100.0, "y": 50.0, "label": "C"}, {"x": 160.0, "y": 80.0, "label": "C"}, {"x": 160.0, "y": 140.0, "label": "C"}, {"x": 100.0, "y": 170.0, "label": "C"}, {"x": 40.0, "y": 140.0, "label": "C"}, {"x": 40.0, "y": 80.0, "label": "C"}]} ``` *(Note: In the complete molecule, each carbon atom is also bonded to two hydrogen atoms to satisfy its tetravalency.)* - **Number of Single Bonds**: There are **18 single bonds** in total (6 $C-C$ single bonds and 12 $C-H$ single bonds).

Carbon and its Compounds

Bonding in Carbon and Saturated/Unsaturated Compounds

Official Answer

(a) Electrical Conductivity of Carbon Compounds

Most carbon compounds are poor conductors of electricity because they form covalent bonds by sharing electrons. In these compounds, no ions or free charged particles are formed to conduct an electric current.

(b) Saturated Ring Compound

Name: Cyclohexane
Formula: $C_6H_{12}$
Structure:

(Note: In the complete molecule, each carbon atom is also bonded to two hydrogen atoms to satisfy its tetravalency.)

Number of Single Bonds: There are 18 single bonds in total (6 $C-C$ single bonds and 12 $C-H$ single bonds).

Covalent bondsNo ionsCyclohexane18 single bondsRing structure

Marking Scheme

1Explanation of poor conductivity due to covalent bonding and absence of ions/free electrons (1 mark)
2Correct name (Cyclohexane) and formula/structure of the ring compound (1 mark)
3Correct count of single bonds (18 single bonds) (1 mark)

Hint

For part (a), think about what is needed to conduct electricity (ions or free electrons). For part (b), think of a six-carbon ring compound with the formula $C_6H_{12}$ and count all the lines representing single covalent bonds.

Quick Oral Answer

Q: Why does cyclohexane have 18 single bonds? A: It has 6 carbon atoms joined in a ring by 6 $C-C$ single bonds, and each carbon is bonded to 2 hydrogen atoms, contributing 12 $C-H$ single bonds, making a total of 18 single bonds.

Analysis & Explanation

According to the NCERT text, carbon compounds have low melting and boiling points because the intermolecular forces between covalent molecules are weak. Since the bonding does not give rise to any ions, they are non-conductors of electricity. Cyclohexane ( $C_6H_{12}$ ) is a classic example of a saturated cyclic hydrocarbon (an alicyclic alkane) where all carbon-carbon bonds are single covalent bonds arranged in a ring skeleton.

Common Mistakes

1Confusing cyclohexane ( $C_6H_{12}$ ) with benzene ( $C_6H_6$ ), which is unsaturated and has alternating double bonds.
2Counting only the 6 carbon-carbon bonds and forgetting to count the 12 carbon-hydrogen bonds, leading to an incorrect answer of 6 single bonds instead of 18.

Interesting Facts

Although graphite is an allotrope of carbon, it conducts electricity exceptionally well because each carbon atom is bonded to only three others, leaving one free valence electron per carbon atom to conduct charge.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2018?

This question carries 3 marks in the CBSE Class 10 Science 2018 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Carbon and its Compounds" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Bonding in Carbon and Saturated/Unsaturated Compounds" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2018 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2018 paper.