21. Which of the following is a characteristic of aromatic compounds?
a) High reactivity
b) Low stability
c) Planar structure
d) Non-planar structure
Answer: c) Planar structure
Explanation: Aromatic compounds have a planar structure which allows for effective overlap of p-orbitals, contributing to their stability and resonance.
22. What is the IUPAC name of the compound C6H5-CH2-CH3?
a) Ethylbenzene
b) Benzyl ethyl
c) Phenethyl
d) Benzene ethane
Answer: a) Ethylbenzene
Explanation: The IUPAC name for C6H5-CH2-CH3 is ethylbenzene, indicating an ethyl group attached to a benzene ring.
23. Which of the following is a key characteristic of alkenes?
a) They cannot undergo addition reactions.
b) They have at least one double bond.
c) They are saturated hydrocarbons.
d) They are less reactive than alkanes.
Answer: b) They have at least one double bond.
Explanation: Alkenes are defined by the presence of at least one double bond between carbon atoms, making them unsaturated hydrocarbons.
24. What type of isomerism can occur in alkenes?
a) Structural isomerism
b) Geometric isomerism
c) Optical isomerism
d) Both a and b
Answer: d) Both a and b
Explanation: Alkenes can exhibit structural isomerism (different connectivity of atoms) and geometric isomerism (cis-trans isomerism) due to restricted rotation around the double bond.
25. Which of the following reactions does not involve the addition of hydrogen?
a) Hydrogenation
b) Hydrohalogenation
c) Halogenation
d) Dehydrogenation
Answer: d) Dehydrogenation
Explanation: Dehydrogenation involves the removal of hydrogen, while hydrogenation, hydrohalogenation, and halogenation all involve the addition of hydrogen or halogens.
26. Which compound can be formed by the hydration of propene?
a) Propanol
b) Butanol
c) Ethanol
d) Acetone
Answer: a) Propanol
Explanation: The hydration of propene in the presence of an acid catalyst leads to the formation of propanol (C₃H₈O), specifically isopropanol (2-propanol).
27. Which of the following has the highest boiling point?
a) Butane
b) 1-Butene
c) 2-Butene
d) 1-Butyne
Answer: d) 1-Butyne
Explanation: 1-Butyne has a higher boiling point compared to butane and alkenes due to the presence of a triple bond, which leads to stronger intermolecular forces.
28. Which of the following statements is true regarding the combustion of aromatic hydrocarbons?
a) Aromatic hydrocarbons burn cleanly without soot.
b) Aromatic hydrocarbons do not produce CO₂.
c) Aromatic hydrocarbons produce soot when burned.
d) Aromatic hydrocarbons do not undergo combustion.
Answer: c) Aromatic hydrocarbons produce soot when burned.
Explanation: The combustion of aromatic hydrocarbons often produces soot due to the incomplete combustion of carbon-rich structures.
29. Which of the following is the correct IUPAC name for 2,3-dimethylpentane?
a) 2,3-Dimethyl-2-pentene
b) 2-Methyl-3-pentene
c) 3,4-Dimethyl-2-pentene
d) 3-Methyl-2-pentene
Answer: a) 2,3-Dimethylpentane
Explanation: The compound is named 2,3-dimethylpentane, indicating that two methyl groups are on the second and third carbon atoms of a pentane chain.
30. What is the product when propene reacts with water in the presence of H₂SO₄?
a) Propanol
b) Propionic acid
c) Ethanol
d) Isopropanol
Answer: d) Isopropanol
Explanation: The reaction of propene with water in the presence of H₂SO₄ results in isopropanol (2-propanol) through Markovnikov’s addition.
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