Question

The average atomic mass of a sample of an element X is 16.2u. What are the percentage of isotopes ({16}^8H) and ({18}^8H) in the sample?

Answer 1

The average atomic mass of a sample X= 16.2 u.

Let the % of isotope of (_{16}^8H) be y and % of isotope of y = (100 – y)%

fi 18y + 1600 = 16y = 1620

fi 2y = 1620 – 1600

∴ 2y = 20

y = 10

Percentage of isotope X = 10%

Percentage of isotope y = 100 - 10 = 90%.