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Past Papers & Board-Style Questions | Organic Chemistry | SM-Educate

Past Papers & Board-Style Questions | Organic Chemistry | SM-Educate
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CS-991 · Module E-1

Past Papers & Board-Style Questions

Exam Preparation Hub
🛈 These are original practice questions written in the style and difficulty level of FBISE board exams — not scanned copies of official past papers. Use them to test your understanding of exam-style phrasing.

📋 Board-Style Practice Questions

A mix of short-answer and long-answer questions covering organic chemistry across Class IX–XII, written in the typical FBISE exam style.

Class IX
Define a homologous series. Give its two characteristics.
Show Answer
Definition: A homologous series is a group of organic compounds with the same general formula and similar chemical properties, where each successive member differs by a CH₂ group.
Characteristics: (1) Same general formula, (2) Gradual change in physical properties (e.g. boiling point) along the series.
Class X
Differentiate between aromatic and aliphatic compounds with one example each.
Show Answer
Aromatic: Contains a benzene ring with special stability (e.g. Benzene, C₆H₆).
Aliphatic: Does not contain a benzene ring; can be open-chain or cyclic (e.g. Methane, CH₄).
Class XI
What is the difference between homolytic and heterolytic bond fission? State the products of each.
Show Answer
Homolytic fission: The bond breaks symmetrically, each atom keeping one electron → produces two free radicals.
Heterolytic fission: The bond breaks unsymmetrically, both electrons go to one atom → produces a carbocation and a carbanion.
Class XII
Explain why the Cannizzaro reaction occurs only in aldehydes without an α-hydrogen.
Show Answer
Aldehydes with an α-hydrogen undergo base-catalysed aldol condensation instead, since the base can remove that α-H to form an enolate. Aldehydes with no α-hydrogen (like benzaldehyde) have no such pathway, so in strong base they instead undergo disproportionation: one molecule is oxidized to a carboxylate while another is reduced to an alcohol.
Class XII
Outline the Williamson synthesis and explain why it works best with primary alkyl halides.
Show Answer
Reaction: R-O⁻Na⁺ + R'-X → R-O-R' + NaX.
The alkoxide ion acts as a nucleophile in an SN2 mechanism, requiring backside attack on the alkyl halide's carbon. Primary halides have the least steric hindrance around that carbon, favouring SN2. Bulkier secondary/tertiary halides instead favour E2 elimination over substitution.
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