Practise 25 real Federal Board questions on Hydrocarbons from 2023 to 2025. See the answer and explanation as soon as you answer.
Hydrocarbons is one of the 11 main chapters in our Federal Board Matric Chemistry question bank (10th class), and about 7% of its real questions come from it. Tayyari Karo has 25 real questions on this chapter from 2023 to 2025; 7 are multiple choice and marked instantly, and the rest are short and long questions with a model answer. By difficulty: 15 medium, 10 easy.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
These are real past-paper questions. Think of your answer first, then open the explanation.
Which gas is widely used for welding and cutting metals?
Answer: D. Acetylene
Acetylene (ethyne) burns with oxygen in the oxy-acetylene torch to give a very high-temperature flame, used for welding and cutting metals.
Halogenation of methane in diffused sunlight does NOT produce:
Answer: C. Carbon Black, C
In diffused (controlled) sunlight, methane undergoes stepwise substitution giving CH₃Cl, CH₂Cl₂, CHCl₃ and CCl₄; carbon black (soot) forms only under a violent/explosive reaction in strong direct sunlight.
Bromine water test is used to indicate the presence of all EXCEPT:
Answer: B. H₃C−CH₃
Bromine water decolorizes in the presence of unsaturation (C=C or C≡C bonds); H₃C−CH₃ (ethane) is saturated and does not react, so it does not decolorize bromine water.
Which of the following is a straight chain hydrocarbon?
Answer: A. C₄H₁₀
C₄H₁₀ as n-butane (CH₃−CH₂−CH₂−CH₃) is an unbranched, straight chain of 4 carbon atoms.
Which compound will discharge the pink color of KMnO₄ solution and will be oxidized?
Answer: B. Ethene
Ethene, being unsaturated, is readily oxidized by KMnO₄ (Baeyer's reagent), decolorizing its pink/purple color; the saturated alkanes (ethane, methane, butane) do not react this way.
The reduction of alkyl halides takes place in the presence of:
Answer: D. Zn + HCl
Alkyl halides are reduced to alkanes using zinc and dilute hydrochloric acid (nascent hydrogen replaces the halogen).
What is homologous series? Give one example.
A homologous series is a group (family) of organic compounds having the same general formula, similar chemical properties, and each successive member differing from the next by a constant unit (usually −CH₂−, 14 amu).
Example: the alkane series — CH₄, C₂H₆, C₃H₈, C₄H₁₀, ... (general formula CₙH₂ₙ₊₂).
Discuss the preparation of ethene by following methods with chemical equations: (a) Dehydration of alcohols (b) Dehydrohalogenation of alkyl halides
(a) Dehydration of alcohols: Ethanol is heated with excess concentrated sulfuric acid (H₂SO₄) at about 170°C, which removes a water molecule (intramolecular dehydration) to form ethene:
CH₃−CH₂−OH --(conc. H₂SO₄, 170°C)--> CH₂=CH₂ + H₂O
(b) Dehydrohalogenation of alkyl halides: Ethyl chloride (or another haloalkane) is heated with alcoholic potassium hydroxide (KOH), which removes a molecule of HCl (elimination reaction) to form ethene:
CH₃−CH₂−Cl + KOH --(alcoholic, Δ)--> CH₂=CH₂ + KCl + H₂O
| Session | Questions |
|---|---|
| 2025 1st Annual | 7 |
| 2025 2nd Annual | 8 |
| 2024 Annual | 6 |
| 2023 Annual | 4 |
25 real Federal Board (FBISE) Chemistry questions on Hydrocarbons from 2023 to 2025, for 10th class. Each one shows the session it came from.
No. We could not find an official FBISE marking scheme for these papers, so the answers and explanations are written by Tayyari Karo for practice. Check anything important with your teacher or textbook.
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