Assertion (A) & Reason (B) MCQ

MCQ 11 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.

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.

View full question & answer→

MCQ 21 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.

✓
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 $A$.

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 $\ce{(CH_3)_2CHCl}.$

View full question & answer→

MCQ 31 Mark

Assertion $(A):$ Rate of addition of $\ce{HCN}$ on carbonyl compounds increases in presence of $\ce{NaCN}.$
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 $A.$

The addition of $\ce{HCN}$ to carbonyl compounds involves the addition of $CN^-$ in rate determining step which are supplied easily by $\ce{NaCN}$ and thus addition becomes fast.

View full question & answer→

MCQ 41 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

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

View full question & answer→

Chemistry Assertion (A) & Reason (B) MCQ

Test yourself on this topic