Question

jmap Base your answer to the question on the information.Naturally occurring elemental carbon is a mixture of isotopes. The percent composition of the two most abundant isotopes is listed below.98.93% of the carbon atoms have a mass of 12.00 atomic mass units.1.07% of the carbon atoms have a mass of 13.00 atomic mass units.Calculate the average atomic mass of carbon.

Answer 1

Answer : The atomic mass of carbon is, 12.01 amu

Explanation :

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

$\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i$

As we are given that,

• Mass of C-12 isotope = 12.00 amu

Percentage abundance of C-12 isotope = 98.93 %

Fractional abundance of C-12 isotope = 0.9893

• Mass of C-13 isotope = 13.00 amu

Percentage abundance of C-13 isotope = 1.07 %

Fractional abundance of C-13 isotope = 0.0107

Now put all the given values in above formula, we get:

$\text{Average atomic mass }=[(12.00\times 0.9893)+(13\times 0.0107)]$

$\text{Average atomic mass }=12.01amu$

Therefore, the atomic mass of carbon is, 12.01 amu