BPSC PGT Chemistry Important Questions- Classification of Organic Compounds

1. Tropolone is a benzenoid compound.
a) True
b) False

Answer: b
Explanation: Tropolone is a non-benzenoid compound because it lacks a benzene ring. On the other hand, benzenoid compounds contain one or more benzene rings, such as benzene, aniline, and naphthalene.

2. What is the other name for acyclic compounds?
a) Aliphatic
b) Aromatic
c) Heterocyclic
d) Alicyclic

Answer: a
Explanation: Acyclic or open-chain compounds are known as aliphatic compounds because they have straight or branched chains. In contrast, aromatic, heterocyclic, and alicyclic compounds are closed-chain or ring structures.

3. Which of these is not an aliphatic compound?
a) Acetic acid
b) Acetaldehyde
c) Ethane
d) Tetrahydrofuran

Answer: d
Explanation: Tetrahydrofuran is a ring (closed-chain) compound, whereas acetic acid, acetaldehyde, and ethane are open-chain compounds and hence classified as aliphatic. Tetrahydrofuran has the molecular formula (CH₂)₄O.

4. The successive members of a homologous series differ by an unit of which of the following?
a) –CH₃
b) CH₃CH₃
c) –CH₂
d) –CH₂CH₃

Answer: c
Explanation: In a homologous series, each successive member differs from the previous one by a CH₂ unit. For example, methanol (CH₃OH), ethanol (CH₃CH₂OH), and propanol (CH₃CH₂CH₂OH) show that the difference between consecutive members is always a CH₂ group.

5. Pick out the option that is not a functional group from the following.
a) Hydroxyl group
b) Benzene group
c) Aldehyde group
d) Carboxylic acid group

Answer: b
Explanation: The benzene group is not considered a functional group. A functional group is an atom or a group of atoms arranged in a specific way that determines the characteristic chemical properties of an organic compound. Examples include the hydroxyl group (–OH), aldehyde group (–CHO), and carboxyl group (–COOH), all of which alter the chemical behavior of hydrocarbons when attached to them.