Which of the following is an unsaturated hydrocarbon? MCQ with Answer and Explanation

Which of the following is an unsaturated hydrocarbon?
A. Propane
B. Cyclohexane
C. Methane
D. Benzene
Answer: Option D
Solution (By JKExamLibrary)
Unsaturated hydrocarbons contain at least one double or triple bond between carbon atoms. Benzene (C6H6) has a ring structure with alternating double bonds (delocalized pi electrons), making it highly unsaturated. Cyclohexane, propane, and methane contain only single bonds and are saturated hydrocarbons.

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Practice More chemistry Questions

Question #1
Niels Bohr's model of the atom introduced the concept of:
A. Wave-particle duality of electrons.
B. Quantized electron orbits.
C. A dense central nucleus.
D. Electrons embedded in a positive sphere.

Correct Answer: Option B


Explanation:
In 1913, Niels Bohr modified Rutherford's model to explain atomic stability and emission spectra. He introduced the concept of quantized electron orbits (or energy levels), stating that electrons revolve in specific, fixed orbits without radiating energy, and they only emit or absorb energy when jumping between these discrete levels.

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Question #2
In the reaction: 2PbO + C → 2Pb + CO₂, which substance is oxidized?
A. CO₂
B. PbO
C. C
D. Pb

Correct Answer: Option C


Explanation:
Oxidation is the gain of oxygen or loss of electrons. Here, Carbon (C) gains oxygen to form Carbon dioxide (CO₂), so Carbon is oxidized. Lead oxide (PbO) loses oxygen to form Lead (Pb), so PbO is reduced. This is a classic redox reaction where both processes occur simultaneously.

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Question #3
Which of the following statements is correct regarding the modern periodic table?
A. Noble gases are in Group 1.
B. There are 8 periods.
C. It is based on atomic mass.
D. Elements in a group have same number of valence electrons.

Correct Answer: Option D


Explanation:
Groups (vertical columns) contain elements with the same number of valence electrons, leading to similar chemical properties. The modern table is based on atomic number; 7 periods exist; noble gases are in Group 18.

This question belongs to: Science chemistry