The 2 most abundant isotopes of carbon are carbon-12 (mass=12.00 amu) and carbon-13 (mass=13.00 amu). Their relative abundance are 98.9% and 1.10%, respectively. Calculate the atomic mass of carbon.

The answer to your question is: 12.011 amu

Explanation:

Carbon - 12 mass = 12.00 amu abundance = 98.9 %

Carbon-13 mass = 13 amu abundance = 1.10 %

atomic mass of carbon = (mass number isotope 1) (abundance) / 100+

(mass number isotope 2) (abundance) / 100

atomic mass of carbon = (12) (0.989) + (13) (0.011) = 11.868 + 0.143

= 12.011 amu