Question

Potassium is isotopic and has RAM of 39.5 work out the percentage abundance of each isotope in a given sample of potassium which is found to contain 3 isotopes of K-39, K-40 and K-38 with the abundance of K-38 being 0.01%

Answer 1

Yo sup??

Let the percentage of K-39 be x

then the percentage of K-40 is 100-(x+0.01)

We know that the net weight should be 39.5. Therefore we can say

(39*x+40*(100-(x+0.01))+38*0.01)/100=39.5  

(since we are taking it in percent)

39*x+40*(100-(x+0.01))+38*0.01=3950

39x+4000-40x-0.4+0.38=3950

2x=49.98

x=24.99

=25 (approx)

Therefore K-39 is 25% in nature and K-40 is 75% in nature.

Hope this helps.