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Chemistry Assertion (A) & Reason (B) MCQ

MODEL PAPER 5 · CBSE STD 12 Science (CBSE - English Medium). 4 questions.

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Assertion (A) & Reason (B) MCQ

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4 questions · timed · auto-graded

MCQ 11 Mark
Assertion (A): With excess of HI, glycerol ultimately gives isopropyl iodide.
Reason (R): The reaction occurs through intermediate formation of allyl iodide and propylene.
  • ✓
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • C
    A is true but R is false.
  • D
    A is false but R is true
Answer
Correct option: A.
Both A and R are true and R is the correct explanation of A.
(a) Both A and R are true and R is the correct explanation of A.
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MCQ 21 Mark
Assertion (A): Vinyl halides do not give nucleophilic substitution reaction.
Reason (R): Vinyl group is electron donating in vinyl halides.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • ✓
    A is true but R is false.
  • D
    A is false but R is true.
Answer
Correct option: C.
A is true but R is false.
(c) A is true but R is false.
Explanation: A is true but R is false.
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MCQ 31 Mark
Assertion (A): Reactivity of ketones is more than aldehydes.
Reason (R): The carbonyl carbon of ketones is less electrophilic as compared to aldehydes.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • C
    A is true but R is false.
  • ✓
    A is false but R is true.
Answer
Correct option: D.
A is false but R is true.
(d) A is false but R is true.
Explanation:
The carbonyl carbon in aldehydes generally has a more partial positive charge than in ketones due to the electron-donating nature of alkyl groups. Aldehydes only have one e-donor group while ketones have two.
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MCQ 41 Mark
Assertion (A): D-glucose and D-mannose form same osazone with phenylhydrazine.
Reason (R): Osazone formation involves only the last four carbon atoms.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • ✓
    A is true but R is false.
  • D
    A is false but R is true.
Answer
Correct option: C.
A is true but R is false.
(c) A is true but R is false.
Explanation: A is true but R is false.
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Assertion (A) & Reason (B) MCQ - Chemistry STD 12 Science Questions - Vidyadip