# How do you determine the average weighted isotopic mass of Carbon?

Feb 5, 2017

Well, first you must quote the percentage isotopic masses of the common isotopes.

#### Explanation:

According to this site, ""^12C has a 99% abundance, and ""^13C has a 1% abundance (there are other isotopes, but these are the most abundant). The weighted average is $\left(12 \times 0.99\right)$ $+ \left(13 \times 0.01\right)$ $\text{amu}$ $=$ $12.01$ $\text{amu}$.

The ""^13C isotope is a very important nucleus inasmuch as ""^13C{""^1H} $\text{NMR spectroscopy}$ can be routinely performed.