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Class 11 Hydrocarbons worksheet
CBSE Chemistry. Alkanes, alkenes, alkynes and benzene: preparation, reactions, Markovnikov, aromaticity. Every sheet has 20 questions in three sections and an answer key, and the numbers change every time.
Sample questions
Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.
Section A · multiple choice
- 1.
The general formula of alkanes is:
- CₙH₂ₙ₋₂
- CₙHₙ
- CₙH₂ₙ
- CₙH₂ₙ₊₂
Answer
(d) CₙH₂ₙ₊₂
- 2.
But-1-ene reacts with HBr in the presence of a peroxide. The main product is:
- 1-bromobutane
- ethanal (two molecules)
- propanone and methanal
- methanal (two molecules)
Answer
(a) 1-bromobutane
anti-Markovnikov (peroxide effect)
- 3.
An open-chain hydrocarbon C₅H₈ has at most one multiple bond. It is an:
- arene
- alkene
- alkyne
- alkane
Answer
(c) alkyne
CₙH₂ₙ₋₂
Section B · short answer
- 4.
State Markovnikov’s rule, with an example.
Answer
When HX adds to an unsymmetrical alkene, the negative part (X) goes to the carbon with fewer hydrogen atoms. CH₃CH=CH₂ + HBr → CH₃CHBrCH₃ (2-bromopropane).
- 5.
Write the balanced equation for the complete combustion of methane. How many moles of oxygen are needed to burn 1 mol of it?
Answer
CH₄ + 2O₂ → CO₂ + 2H₂O; 2 mol
balance C, then H, then O
Section C · long answer
- 6.
Describe three methods of preparing alkanes, with equations.
Answer
From alkenes and alkynes by hydrogenation over Ni, Pt or Pd: CH₂=CH₂ + H₂ → CH₃CH₃. From alkyl halides by the Wurtz reaction: 2CH₃Br + 2Na → C₂H₆ + 2NaBr (dry ether). From carboxylic acid salts by decarboxylation with soda lime: CH₃COONa + NaOH → CH₄ + Na₂CO₃; or by Kolbe’s electrolysis.
Fresh sheets for your child
In the app, every Hydrocarbons sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.
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