Answer to Question #109451 in General Chemistry for Anastasia

Question

how do you calculate the abundance of carbon-12?

Answer 1

Solution:

The relative atomic mass of carbon is known to be 12.011AU.

Two stable carbon isotopes are known, namely C¹² and C¹³. The atomic masses of these isotopes are respectively equal to 12.0000AU and 13.0034AU.

A very small amount of unstable isotopes (C¹¹ and C¹⁴) can be ignored for this calculation.

Let's denote the variable X to the abundance of C¹², then abundance of C¹² will be 1-X.

Thus, we get an equation with one unknown X:

12*X+13.0034*(1-X)=12.011

1.0034*X=0,9924

X=0.989 or 98.9%

Answer:

the abundance of carbon-12 is 98.9%