Question

Assertion (A): A single C-12 atom has a mass exactly 12 amu and a mole of these atoms has a mass of exactly 12 grams.

Reason (R): A mole of atoms of any element has a mass in grams equal to its atomic mass.

पर्याय

• If both A and R are true, and R is the correct explanation of A.

• If both A and R are true, but R is not the correct explanation of A.

• If A is true, but R is false.

• If both A and R are false.

Answer 1

If both A and R are true, but R is not the correct explanation of A.

Explanation:

The assertion is true because the atomic mass unit (amu) is explicitly defined using the carbon-12 isotope, making one atom exactly 12 amu and one mole exactly 12 grams. The reason is also true because the molar mass of any element in grams always numerically matches its atomic mass. However, R is not the correct explanation for A because the exact 12-gram value of a C-12 mole is a direct consequence of the baseline definition of Avogadro's number and the amu scale, rather than a derivation from a general rule applied to other elements.