Question

How would you find the average atomic mass of sulphur from the following data: $S-3295.002\mathrm{\%}(31.972),S-330.76\mathrm{\%}(32.971),S-344.22\mathrm{\%}(33.967),andS-360.014\mathrm{\%}(35.967)$?

Answer 1

Hint: The average atomic mass of a chemical is going to be calculated based on the atomic mass of the isotopes and their respective percentage of abundances in nature. The formula to calculate the average atomic mass of an element is as follows:
$$Averageatomicmass=\sum _i(isotop{e}_i\times abundance{e}_i)$$
Here i = number of isotopes of the element

Complete answer:
- In the question it is asked to calculate the average atomic mass of sulphur from the data provided.
- The given data shows that sulphur atom has four isotopes in nature and the given data is as follows.

S. No	Isotope of sulphur	Atomic weight	Percentage of abundance
1	${}^{32}S$	31.972	95.002
2	${}^{33}S$	32.971	0.76
3	${}^{34}S$	33.967	4.22
4	${}^{36}S$	35.967	0.014

- The average atomic mass of the sulphur can be calculated from its isotopes and it is as follows.
$Averageatomicmass=(31.972)\ast (95.002)+(32.917)\ast (0.76)+(33.967)\ast (4.22)+(35.967)\ast (0.014)=32.063$
Therefore the calculated average atomic mass of the sulphur from its isotopes is 32.063.

Note: Without knowing the atomic weights and percentages of abundance of the isotopes of an element we cannot calculate the average atomic mass of the element. The sum of the product of percentage of abundance of isotopes and atomic weights of the isotopes will give the average atomic weight of the element.