Question

Carbon occurs in nature as a mixture of carbon-12 and carbon-13. The average atomic mass of carbon is 12.011. What is the percentage abundance of carbon-12 in nature?

• A. 98.90 %
• B. 54.40 %
• C. 65.78%
• D. 78.99 %

Answer 1

The correct option is A 98.90 %

Let the percentage abundance of carbon-12 be $x$.
Then the percentage abundance of carbon-13 will be $100-x$
$\text{Average atomic mass}=\frac{12x+13(100-x)}{100}=12.011$
$x=98.90\%$