IsotopeRelative Abudance(%)Atomic Mass(amu)12C98.8921213C1.10813.0033514C2×10−1014.00317
From the data given in the table, calculate the average atomic mass of C
12.011 u
Average atomic mass is the weighted average of atomic mass of all the isotopes.
Contribution by each isotope = (Relative abundance) (Atomic mass)
Contribution by
126C = (0.98892)(12)/100 = 11.86704
136C = (0.01108)(13.00335)/100 = 0.14407712
146C = (2 × 10−10)(14.003170/100 = 28.00634 × 10−12
∴ Average atomic mass = sum of all contribution = 12.011 u