Consider the carbon compounds having following molecular formula:
(i) (ii) (iii) (iv) (v)
(a) State the number of double covalent bonds present in
(b) Write the formula of first member of the homologous series to which the carbon compound belongs.
(c) Which one of the above compounds forms ring structure of carbon atoms?
(d) Identify, which of the above compounds, is a member of alkane series.
Consider the carbon compounds having following molecular formula:
(i) (ii) (iii) (iv) (v)
(a) State the number of double covalent bonds present in
(b) Write the formula of first member of the homologous series to which the carbon compound belongs.
(c) Which one of the above compounds forms ring structure of carbon atoms?
(d) Identify, which of the above compounds, is a member of alkane series.
Official answer
(a) There is double covalent bond present in (propene).
(b) The compound (butyne) belongs to the alkyne homologous series (general formula ). The first member of this series is ethyne, which has the molecular formula .
(c) Both (benzene) and (cyclohexane) form ring structures of carbon atoms.
(d) (propane) is a member of the alkane series (general formula ).
Marking scheme
- 1.State 1 double bond for (a) (0.5 marks)
- 2.Identify ethyne / as the first member for (b) (0.5 marks)
- 3.Identify and/or as ring structures for (c) (0.5 marks)
- 4.Identify as the alkane for (d) (0.5 marks)
Hint
Recall the general formulas: Alkanes = , Alkenes = , Alkynes = . Remember that the simplest alkyne must contain at least two carbon atoms.
Quick oral answer
Q: Why can't a one-carbon alkyne exist? A: An alkyne requires a carbon-carbon triple bond (), which is only possible if there are at least two carbon atoms. Therefore, the simplest alkyne is ethyne ().
Common mistakes
- 1.Writing the first member of the alkyne series as methyne (CH) instead of ethyne (). A triple bond requires at least two carbon atoms.
- 2.Confusing cyclohexane () with hexane () or benzene ().
- 3.Miscalculating the number of double bonds in propene as more than one.
Analysis and explanation
This question tests the student's ability to identify and classify organic compounds based on their molecular formulas. By applying the general formulas for alkanes (), alkenes (), and alkynes (), students can determine the degree of unsaturation and homologous series. It also evaluates their understanding of cyclic hydrocarbons like cyclohexane and benzene.
Interesting facts
Ethyne is commonly known as acetylene and is widely used in gas welding due to the extremely high temperature of its flame when burnt with oxygen.
Benzene was discovered by Michael Faraday in 1825 and has a unique cyclic structure with alternating double bonds that exhibits resonance stability.
Question details
Q7 of 15 questions
- Board
- CBSE
- Class
- Class 10
- Subject
- Science
- Year
- 2022
- Section
- Section A
- Marks
- 2
- Type
- Short Answer
- Chapter
- Carbon and its Compounds
- Topic
- Saturated and Unsaturated Carbon Compounds, Chains, Branches and Rings
- Bloom's level
- Applying
- Syllabus topic
- Covalent bonding in carbon compounds. Versatile nature of carbon. Homologous series.
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Frequently asked questions
How many marks does this question carry in CBSE Class 10 Science 2022?
This question carries 2 marks in the CBSE Class 10 Science 2022 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 "Saturated and Unsaturated Carbon Compounds, Chains, Branches and Rings" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2022 paper?
This is a Short Answer question from Section A in the CBSE Class 10 Science 2022 paper.