Question

a sample of an element x consists of two isotopes 79 35 x ad 81 35 x if the average atomic mass of this sample of element be 80.4 u calculate the percentage of the two isotopes in this sample

Answer 1

Answer:

Element A whose atomic mass having 79.35 having 47.5%,Element B whose atomic mass having 81.35 having 52.5%

Answer 2

The isotope with 79u is 30% in the sample and the isotope with 81u is 70%

Explanation:

Given the average atomic weight is 80.4u

Let the isotope with 79u be available x%

and the isotope with 81u will be available (100-x)%

Average atomic weight= sum of (atomic weight of each element× percentage availability)/100

i.e,

80.4=$\frac{79x + (81)(100-x)}{100}$

i.e, 8040=8100-2x

2x=60

x=30

100-x =70