11. Which compound is known as the simplest alkyne?
a) Ethylene
b) Propylene
c) Acetylene
d) Butyne
Answer: c) Acetylene
Explanation: Acetylene (C₂H₂) is the simplest alkyne, consisting of two carbon atoms connected by a triple bond.
12. What is the general formula for alkenes?
a) CnH₂n-2
b) CnH₂n+2
c) CnH₂n
d) CnH₂n-1
Answer: c) CnH₂n
Explanation: The general formula for alkenes is CnH₂n, indicating that for every n carbon atoms, there are 2n hydrogen atoms, with at least one double bond present.
13. Which of the following statements is true about the stability of alkenes?
a) More substituted alkenes are less stable.
b) Less substituted alkenes are more stable.
c) More substituted alkenes are more stable.
d) Alkenes do not have stability considerations.
Answer: c) More substituted alkenes are more stable.
Explanation: More substituted alkenes (such as tetrasubstituted alkenes) are more stable due to hyperconjugation and the inductive effect from alkyl groups.
14. Which reaction is used to test for the presence of unsaturation in hydrocarbons?
a) Bromine water test
b) Litmus test
c) Baeyer’s test
d) Tollen’s test
Answer: a) Bromine water test
Explanation: The bromine water test is used to identify unsaturation in hydrocarbons. When an alkene or alkyne is present, the reddish-brown bromine water decolorizes.
15. What is the hybridization of the carbon atoms in ethyne?
a) sp
b) sp²
c) sp³
d) dsp²
Answer: a) sp
Explanation: In ethyne (C₂H₂), the carbon atoms are sp hybridized due to the presence of a triple bond, which consists of one sigma bond and two pi bonds.
16. Which of the following is a characteristic reaction of aromatic compounds?
a) Addition reactions
b) Substitution reactions
c) Elimination reactions
d) Hydrolysis reactions
Answer: b) Substitution reactions
Explanation: Aromatic compounds predominantly undergo electrophilic substitution reactions, where an electrophile replaces one of the hydrogen atoms on the aromatic ring.
17. Which of the following alkenes can exhibit cis-trans isomerism?
a) 1-Butene
b) 2-Butene
c) 1-Pentene
d) 1-Hexene
Answer: b) 2-Butene
Explanation: 2-Butene can exhibit cis-trans isomerism due to the presence of two different substituents on either side of the double bond, allowing for different spatial arrangements.
18. What type of bond is formed between carbon atoms in an alkyne?
a) Single bond
b) Double bond
c) Triple bond
d) Quadruple bond
Answer: c) Triple bond
Explanation: Alkynes contain a triple bond between carbon atoms, which consists of one sigma bond and two pi bonds.
19. Which of the following compounds is a terminal alkyne?
a) 1-Butyne
b) 2-Butyne
c) 1-Pentyne
d) 3-Hexyne
Answer: a) 1-Butyne
Explanation: 1-Butyne is a terminal alkyne as it has the triple bond located at the end of the carbon chain.
20. What is the main product of the combustion of hydrocarbons?
a) Carbon dioxide and water
b) Carbon monoxide and water
c) Carbon and hydrogen
d) Alkane and alkene
Answer: a) Carbon dioxide and water
Explanation: The complete combustion of hydrocarbons produces carbon dioxide (CO₂) and water (H₂O) as the main products.
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