Chemistry-Atomic & Molecular Mass

NEET Chemistry Atomic & Molecular Mass Assertion Reason Question

Type: Assertion Reason-assertion-Hard-Class 11

Assertion (A): The atomic mass of carbon-12 is exactly 12 atomic mass units. | Reason (R): The mass of a carbon-12 atom is determined by a mass spectrometer as 1.992648 × 10^-23 g.

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.

Correct Answer

Option B

Detailed Explanation

The atomic mass of carbon-12 is defined as exactly 12 atomic mass units by definition, not because of its measured mass. The mass spectrometer value provides the basis for calculating Avogadro's number, not directly defining atomic mass units.

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