Question

39. Assertion (A) : One atomic mass unit is defined as one twelfth of the mass of
one carbon-12 atom.
Reason (R) : Carbon-12 isotope is the most abundunt isotope of carbon
and has been chosen as standard.
(i) Both A and Rare true and R is the correct explanation of A.
(ii) Both A and Rare true but R is not the correct explanation of A.
(iii) A is true but R is false.
(iv) Both A and R are false.​

Answer 1

Both A and R are true and R is correct explanation of A.

Also one more reason is that there are equal number of protons and neutrons that is 6 in Carbon - 12 isotope. So it was concluded that carbon will be the best atom for comparison of atomic masses of other elements' atom as it had exactly 12 atomic mass.

Answer 2

Answer:

Both A and R are true and R is the correct explanation of A.

Explanation:

Just like it.