Chapter 10: Haloalkanes & Haloarenes
NCERT Solutions for CBSE Class 10 Chemistry — 11 solved questions with detailed explanations.
Solved Questions
Q1. The order of reactivity of alkyl halides in Sₙ₂ reactions is:
- Primary > Secondary > Tertiary
- Tertiary > Secondary > Primary
- All equal
- Secondary > Primary > Tertiary
Difficulty: Easy-Medium · Topic: SN2 Reactions
Solution
Sₙ₂: backside attack. Steric hindrance increases from 1° to 3°, so reactivity: 1° > 2° > 3°.
Q2. Grignard reagent (RMgX) reacts with CO₂ followed by hydrolysis to give:
- Aldehyde
- Ketone
- Carboxylic acid
- Alcohol
Difficulty: Easy-Medium · Topic: Grignard
Solution
RMgX + CO₂ → RCOOMgX →(H₂O/H⁺) RCOOH. Gives carboxylic acid.
Q3. The reaction of chlorobenzene with NaOH at 623 K and 300 atm is called:
- Kolbe's reaction
- Dow's process
- Wurtz reaction
- Fittig reaction
Difficulty: Easy-Medium · Topic: Named Reactions
Solution
Dow's process: PhCl + NaOH →(623K, 300atm) PhOH + NaCl. Industrial phenol synthesis.
Q4. Elimination reactions produce:
- alcohols
- alkenes
- ethers
- alkanes
Difficulty: Easy-Medium · Topic: Haloalkanes & Haloarenes
Q5. Saytzeff rule states that:
- both equally
- less substituted
- more substituted alkene is major product
- no preference
Difficulty: Easy-Medium · Topic: Haloalkanes & Haloarenes
Solution
more substituted alkene is major product.
Q6. Aryl halides are less reactive in Sₙ reactions because:
- they are less stable
- C-X bond is weak
- they are more polar
- C-X bond has partial double bond character
Difficulty: Easy-Medium · Topic: Haloalkanes & Haloarenes
Solution
C-X bond has partial double bond character.
Q7. Finkelstein reaction converts:
- R-I to R-Cl
- R-Cl/R-Br to R-I using NaI/acetone
- R-OH to R-X
- R-NH₂ to R-X
Difficulty: Easy-Medium · Topic: Haloalkanes & Haloarenes
Solution
R-Cl/R-Br to R-I using NaI/acetone.
Q8. Wurtz reaction involves:
- esterification
- dehydration
- polymerization
- R-X + Na → R-R (higher alkane)
Difficulty: Easy-Medium · Topic: Named Reactions
Solution
Wurtz reaction: R-X + Na → R-R (higher alkane).
Q9. Friedel-Crafts alkylation involves:
- Electrophilic substitution with R-X/AlCl₃
- addition
- reduction
- elimination
Difficulty: Easy-Medium · Topic: Named Reactions
Solution
Friedel-Crafts alkylation: Electrophilic substitution with R-X/AlCl₃.
Q10. Kolbe electrolysis involves:
- oxidation
- dehydration
- RCOO⁻ electrolysis → R-R + CO₂
- esterification
Difficulty: Easy-Medium · Topic: Named Reactions
Solution
Kolbe electrolysis: RCOO⁻ electrolysis → R-R + CO₂.
Q11. Cannizzaro reaction involves:
- addition
- condensation
- Aldehyde without α-H + NaOH → acid + alcohol
- substitution
Difficulty: Easy-Medium · Topic: Named Reactions
Solution
Cannizzaro reaction: Aldehyde without α-H + NaOH → acid + alcohol.
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