Question 11 markVery Short AnswerSection A

Write the name and formula of the 2nd member of homologous series having general formula CnH2nC_nH_{2n}.

Carbon and its Compounds
Homologous Series

Official answer

The general formula CnH2nC_nH_{2n} represents the homologous series of alkenes (unsaturated hydrocarbons with one double bond). The first member of this series is ethene (C2H4C_2H_4) where n=2n=2. Therefore, the second member is propene, which has the molecular formula C3H6C_3H_6.

Answer keywords:PropeneC3H6C_3H_6Alkenes

Marking scheme

  1. 1.Name: Propene (0.5 mark)
  2. 2.Formula: C3H6C_3H_6 (0.5 mark)

Hint

Recall that the alkene series starts with two carbon atoms because a double bond cannot exist with only one carbon atom.

Quick oral answer

The second member of the CnH2nC_nH_{2n} series is propene (C3H6C_3H_6). It belongs to the alkene family, characterized by at least one carbon-carbon double bond.

Common mistakes

  1. 1.Writing 'methene' as the first member (it does not exist).
  2. 2.Confusing the formula with alkanes (CnH2n+2C_nH_{2n+2}) or alkynes (CnH2n−2C_nH_{2n-2}).

Analysis and explanation

The general formula for alkenes is CnH2nC_nH_{2n}. Since a double bond requires at least two carbon atoms, the series starts with n=2n=2.

  • 1st member (n=2n=2): Ethene (C2H4C_2H_4)
  • 2nd member (n=3n=3): Propene (C3H6C_3H_6)
  • 3rd member (n=4n=4): Butene (C4H8C_4H_8)

Interesting facts

Propene is the second simplest alkene and is a byproduct of oil refining and natural gas processing.

Question details

Q1 of 36 questions

Board
CBSE
Class
Class 10
Subject
Science
Year
2015
Section
Section A
Marks
1
Type
Very Short Answer
Chapter
Carbon and its Compounds
Topic
Homologous Series
Bloom's level
Remembering
Syllabus topic
Homologous series

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Frequently asked questions

How many marks does this question carry in CBSE Class 10 Science 2015?

This question carries 1 mark in the CBSE Class 10 Science 2015 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 "Homologous Series" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2015 paper?

This is a Very Short Answer question from Section A in the CBSE Class 10 Science 2015 paper.