Four statements about members of the same homologous series are listed.
- They have the same volatility.
- They have the same molecular formula.
- They have the same functional group.
- They have the same general formula.
Which statements are correct?
A) 1 and 2
B) 1 and 4
C) 2 and 3
D) 3 and 4
▶️ Answer/Explanation
Ans: D
Members of a homologous series have the same functional group (3) and the same general formula (4). They do not have the same molecular formula (2 is incorrect) as each successive member differs by CH2. Volatility (1) decreases as chain length increases, so this is incorrect. Therefore, the correct statements are 3 and 4.
Which statement about compounds in the same homologous series is correct?
A) They have the same chemical properties because they have the same number of carbon atoms.
B) They have the same physical properties because they have the same number of carbon atoms.
C) They have different chemical properties because they have different numbers of carbon atoms.
D) They have different physical properties because they have different numbers of carbon atoms.
▶️ Answer/Explanation
Ans: D
Compounds in a homologous series have similar chemical properties but gradually changing physical properties as the number of carbon atoms increases. The key points are:
1. All members have the same functional group, giving them similar chemical properties (options A and C are incorrect about chemical properties).
2. As chain length increases, physical properties like boiling point change systematically (option B is incorrect about physical properties).
3. Option D correctly states that different numbers of carbon atoms lead to different physical properties while maintaining similar chemical properties.
Which compounds have similar chemical properties?
A) butanol and butanoic acid
B) ethane and ethene
C) methane and butane
D) propene and propanol
▶️ Answer/Explanation
Ans: C
Compounds in the same homologous series have similar chemical properties. Methane and butane are both alkanes (C is correct). The other pairs belong to different functional groups: butanol (alcohol) and butanoic acid (carboxylic acid, A); ethane (alkane) and ethene (alkene, B); propene (alkene) and propanol (alcohol, D). Only option C represents two members of the same homologous series.
Four statements about organic compounds P, Q, R and S are listed.
P is a saturated hydrocarbon.
The formula of Q is CH3CH3.
A molecule of R contains only one oxygen atom.
Compound S is a carboxylic acid.
Which statement about these compounds is correct?
A) P and Q are members of different homologous series.
B) P and S are members of the same homologous series.
C) Q and S are members of the same homologous series.
D) Q, R and S are all members of different homologous series.
▶️ Answer/Explanation
Ans: D
Let’s analyze each compound:
P is a saturated hydrocarbon (alkane series).
Q (CH3CH3) is ethane, also an alkane.
R has one oxygen atom – could be an alcohol, ether, or aldehyde (different from P and Q).
S is a carboxylic acid (completely different functional group).
Option D is correct because Q (alkane), R (could be alcohol/ether), and S (carboxylic acid) are indeed from different homologous series.