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Hydrocarbons
Written by Dr. Ayesha Nadeem (Chemistry)
8 Class 12 Chemistry questions with answers and explanations.
Printable worksheet with answer key
All questions with answers
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Benzene has the formula:
- 1 C6H6
- 2 C5H5
- 3 C6H14
- 4 C6H12
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Correct answer: C6H6
Benzene is C6H6.
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Alkenes mainly undergo:
- 1 No reactions
- 2 Elimination only
- 3 Substitution reactions only
- 4 Addition reactions
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Correct answer: Addition reactions
The double bond opens to add atoms.
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The hybridisation of carbon in ethene is:
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Correct answer: sp2
Each carbon in ethene forms three sigma bonds, so sp2.
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Addition of HBr to propene follows Markovnikov's rule to give mainly:
- 1 Bromopropene
- 2 1-bromopropane
- 3 2-bromopropane
- 4 Propane
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Correct answer: 2-bromopropane
Hydrogen adds to the carbon with more hydrogens, so bromine goes on the middle carbon.
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Benzene reacts mainly by:
- 1 Nucleophilic addition
- 2 Addition
- 3 Free radical chain only
- 4 Electrophilic substitution
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Correct answer: Electrophilic substitution
The stable ring is kept and a hydrogen is replaced.
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The compound CH3CH=CH2 is:
- 1 Butene
- 2 Propyne
- 3 Propene
- 4 Propane
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Correct answer: Propene
It has three carbons and a double bond.
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The test that distinguishes alkenes from alkanes is:
- 1 Fehling's solution
- 2 Bromine water
- 3 Tollens' reagent
- 4 Litmus
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Correct answer: Bromine water
Alkenes decolourise bromine water.
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Ethyne is also known as:
- 1 Acetylene
- 2 Ethylene
- 3 Methane
- 4 Benzene
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Correct answer: Acetylene
Acetylene is the common name.
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