Asked by 0oooooooo0

Bromine has two isotopes, Br- 79 and Br- 81. The relative atomic mass of bromine is 79.9.

CALCULATE THE PERCENTAGE of Br-79 atoms in a sample of bromine.



PLease help i'm really stuck

Someone said:
The total for 79 and 81 is 100% and the total for fraction is 1, so
let X = fraction 79 and 1-X = fraction of 81.
Then 79(X) + 81(1-X) = 79.9
Solve for X.


I dont get it the total is 160 and there are 2 numbers so 2 fractions? and I dont get the x thing with 1-x AND 79(X)+81(1-X) iM VERY CONFUSED PLEASE HELP.
I need a simple clear explanation please.

Answered by bobpursley
assume you have x percent of 79. Then you have 100-x percent of 81, and you have 100 percent of the mixture.

x*79+(100-x)81=79.9*100
solve for x, then 100-x.
Of course there are two fractions, each isotope has a differing content. Now if you cant solve that equation above, you have very serious chemistry issues ahead, this is algebra I.

Answered by 0oooooooo0
is it 40.1 percent??
Answered by Tricia
It’s 55%