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Chemistry Assertion (A) & Reason (B) MCQ

MODEL PAPER 9 · 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): Ortho-nitrophenol is more acidic than phenol.
Reason (R): Nitro group is electron donating group and therefore stabilizes ortho-nitrophenoxide ion.
  • 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 21 Mark
Assertion (A): In comparison to ethyl chloride it is difficult to carry out nucleophilic substitution on vinyl chloride.
Reason (R): Vinyl group is electron-donating.
  • 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: $CH _2= CH - Cl$ has some partial double bond character between carbon and a chlorine atom. So, nucleophilic substitution is difficult to carry as it is difficult to break the partial double bond in vinyl chloride than ethyl chloride $CH _3 CH _2$
→ Cl where there is no double bond character.
The vinyl group is not electron-donating. The carbon halogen bond in vinyl halides has some double-bond character and thus a little difficult to break.
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MCQ 31 Mark
Assertion (A): Halogen acids do not add on to carbonyl bond.
Reason (R): Addition depends upon the polarisation of HX and carbonyl bond.
  • ✓
    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 .
Explanation: Both A and R are true and R is the correct explanation of A .
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MCQ 41 Mark
Assertion (A): At isoelectric point, the amino group does not migrate under the influence of electric field.
Reason (R): At isoelectric point, amino acid exists as a zwitterion.
  • 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.
  • D
    A is false but R is true.
Answer
(a) Both A and R are true and R is the correct explanation of A.
Explanation: The high degree of polarity in HX as well as in carbonyl bond shows the easy addition of HX on carbonyl bond but as soon as the addition products are formed, the products loses HX to show the backward reaction.
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Assertion (A) & Reason (B) MCQ - Chemistry STD 12 Science Questions - Vidyadip