Assertion (A) & Reason (B) MCQ

Question 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

Answer

(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

group and reduce Tollen's reagent, Schiff's reagent or Benedict's solution.

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Question 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.

Answer

Aqueous solution of phenol is called carbolic acid. Electron withdrawing groups such as $-NO_2, -CN, -X-$ 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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Question 31 Mark

Assertion $(A):$ Isopropyl chloride is less reactive than $\ce{CH_3Br}$ in $S_N2$ reactions.
Reason $(R): SN^2$ reactions are always accompanied by inversion of configuration.

Answer

As the size of the alkyl groups increases, the $S_N2$ reactivity decreases, further $C - Cl$ bond is stronger and more difficult to cleave than $C - Br$ bond. So $\ce{CH_3Br}$ is more reactive than $\ce{(CH_3)_2CHCl.}$

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Question 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.

Answer

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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Chemistry Assertion (A) & Reason (B) MCQ

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