Question

What is the average atomic mass of chlorine if the mass of one isotope is 34.97 amu and has a p?er cent abundance of 75.77%. The other isotope has a mass of 36.97 amu and has a percent abundance of 24.23%

Answer 1

Answer : The average atomic mass of chlorine is, 32.37 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 isotope 1 = 34.97 amu

Percentage abundance of isotope 1 = 75.77 %

Fractional abundance of isotope 1 = 0.7577

Mass of isotope 2 = 36.97 amu

Percentage abundance of isotope 2 = 24.23 %

Fractional abundance of isotope 2 = 0.2423

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

$\text{Average atomic mass of element}=\sum[(34.97\times 0.7577)+(24.23\times 0.2423)]$

$\text{Average atomic mass of element}=32.37amu$

Therefore, the average atomic mass of chlorine is, 32.37 amu