Question

Carbon occurs in nature as a mixture of $^{12}C$ and $^{13}C$. The average atomic mass of carbon is $12.011$. What is the $\%$ abundance of $^{12}C$ in nature?

• A. $89\%$
• B. $98.9\%$
• C. $89.9\%$
• D. $79.9\%$

Answer 1

Answer: (B)

Let $\% $abundance of $^{12}C = x $
$ \%$ abundance of $^{13}C =100-x $
$ \because \frac{12x}{100} +\frac{13\left(100-x\right)}{100} = 12.011 $
$ 12x+1300-13x= 1201.1$
$ \Rightarrow x=98.9$
Thus, $\% $ abundance of $^{12}C$ is $98.9\%$