The two most abundant isotopes of carbon are carbon-12 (mass = 12.00 amu) and carbon-13 (mass = 13.00 amu). their relative abundances are 98.9% and 1.10%, respectively. calculate the average atomic mass of carbon.

The answer to your question is: Average atomic mass = 12.011 amu

Explanation:

Data

Carbon -12   mass 12 amu   abundance = 98.9%

Carbon -13   mass 13 amu   abundance = 1.10%

Average atomic mass = ?

Process

Average atomic mass = (Isotope1 x abundance) + (Isotope2 x abundance)

Average atomic mass = (12 x 0.989) + (13 x 0.011)

Average atomic mass = 11.868 + 0.143

Average atomic mass = 12.011

not clear