Assertion (A) & Reason (B) MCQ

MCQ 11 Mark

Assertion (A): 232.508 can be written as $2.32508 \times 10^2$ in scientific notation.
Reason (R): While writing $2.32508 \times 10^2$, the decimal had to be moved to the left by two places and the same is the exponent (2) of 10 in the scientific notation.

✓
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
Both A and R are false.

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: 232.508 can be written as $2.32508 \times 10^2$ in scientific notation. While writing it, the decimal had to be moved to the left by two places and the same is the exponent (2) of 10 in the scientific notation.

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MCQ 21 Mark

Assertion (A): In Sommerfeld's model, circular orbit is possible for the electron in K shell.
Reason (R): Electron present in $K$ shell corresponds to principal quantum number $n =1$.

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
Both A and R are false.

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: Sommerfeld's model is an extension of Bohr's model. Electrons in an atom revolve around the nuclei in elliptical orbit. The circular path is a special case of the elliptical orbit. The Association of elliptical orbit with circular orbit explains the fine line spectrum of atoms.

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MCQ 31 Mark

Assertion (A): Overlapping in benzene is $sp ^2- sp ^2$ type.
Reason (R): C-C bond length in benzene is $1.3 \stackrel{\circ}{A}$.

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
Both A and R are false.

Answer

Correct option: C.

A is true but R is false.

(c) A is true but R is false.
Explanation: C-C bond length in benzene is $1.39 \stackrel{o}{A}$ which is greater than C=C bond length of $1.34 \stackrel{o}{A}$ and less than C-C bond length of $1.54 \stackrel{\circ}{A}$.

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MCQ 41 Mark

Assertion (A): Sodium extract is made alkaline in the test of sulphur.
Reason (R): On reacting with $FeCl _3$, alkaline sodium extract, gives red colour.

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: In the Lassaigne's test for sulphur, sodium extract is made acidic before the addition of lead acetate, because the black precipitate of lead sulphide is insoluble in acidic medium.

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Chemistry Assertion (A) & Reason (B) MCQ

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