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Chemistry Assertion (A) & Reason (B) MCQ [1M]

MODEL PAPER 4 · Bihar Board (BSEB) STD 12 Science (BSEB - English Medium). 4 questions.

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Assertion (A) & Reason (B) MCQ [1M]

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MCQ 11 Mark
Assertion (A): Glucose and fructose are reducing sugars.
Reason (R): Glucose and fructose contain a free aldehydic and ketonic group adjacent to a >CHOH group respectively
  • ✓
    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: Reducing sugars contain a free aldehydic or ketonic groupadjacent to a Image group and reduce Tollen's reagent, Schiff's reagent or Benedict's solution.
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MCQ 21 Mark
Assertion (A): Aqueous solution of phenol is called as carbonic acid.
Reason (R): Increasing order of acidity of phenols is m nitrophenol >o-nitrophenol >p-nitrophenol.
  • 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.
  • ✓
    Both A and R are false.
Answer
Correct option: D.
Both A and R are false.
(d) Both A and R are false.
Explanation:
Aqueous solution of phenol is called carbolic acid. Electron withdrawing groups such as -NO2, -CN, -X- increase the acidity.
The increase is more at o and p - positions than at m-position.
i.e. p-nitrophenol >o-nitrophenol >m-nitrophenol.
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MCQ 31 Mark
Assertion (A): Isopropyl chloride is less reactive than CH3Br in SN2 reactions.
Reason (R): SN2 reactions are always accompanied by inversion of configuration.
  • A
    Both A and R are true and R is the correct explanation of A.
  • ✓
    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: B.
Both A and R are true but R is not the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
Explanation: As the size of the alkyl groups increases, the SN2 reactivity decreases, further C - Cl bond is stronger and more difficult to cleave than C - Br bond. So CH3Br is more reactive than (CH3)2CHCl.
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MCQ 41 Mark
Assertion (A): Rate of addition of HCN on carbonyl compounds increases in presence of NaCN.
Reason (R): Reaction involves the addition of Cn in rate determining step.
  • ✓
    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: The addition of HCN to carbonyl compounds involves the addition of CN- in rate determining step which are supplied easily by NaCN and thus addition becomes fast.
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Assertion (A) & Reason (B) MCQ [1M] - Chemistry STD 12 Science Questions - Vidyadip