Calculating % Abundance of Br-79 & Br-81

  • Thread starter Thread starter sjung915
  • Start date Start date
  • Tags Tags
    Abundance Percent
AI Thread Summary
To calculate the percent abundance of the bromine isotopes Br-79 and Br-81, the atomic weights of both isotopes and the average atomic weight of bromine are used. The initial equation incorrectly assumes equal abundances for both isotopes, which is not the case. The correct approach involves using two variables to represent the different abundances and setting up a system of equations: one for the weighted average and another for the total abundance. The final results indicate that Br-79 has an abundance of approximately 50.66% and Br-81 about 49.33%. This method ensures accurate calculations for isotope abundance based on their respective weights.
sjung915
Messages
4
Reaction score
0

Homework Statement


Naturally occurring bromine contains two isotopes; Br-79, which has a weight of 78.9183 and Br-81 with a weight of 80.9163. If the atomic weight of Br is 79.904, determine the % abundance of Br-79 and Br-81.

Homework Equations



To solve this equation I try to put the equation as

(x)(78.9183) + (x)(80.9163) = 79.904

The value of x = .499946789



The Attempt at a Solution



The answers were given because this is a practical exam I'm studying for. Can someone point me in the right direction. Something seems to be missing from the equation.


Br-81 49.33%
Br-79 50.66%
 
Physics news on Phys.org
Nevermind I found the answer.. Thank you
 
For the record:

sjung915 said:
(x)(78.9183) + (x)(80.9163) = 79.904

is wrong, as abundances of both isotopes are different, not identical - so you need two variables. The correct equation is

(x1)(78.9183) + (x2)(80.9163) = 79.904

and you need another equation:

x1 + x2=1
 

Thread 'Prove that evolution is constant (Provide at least two arguments to support your position)'

I don't get how to argue it. i can prove: evolution is the ability to adapt, whether it's progression or regression from some point of view, so if evolution is not constant then animal generations couldn`t stay alive for a big amount of time because when climate is changing this generations die. but they dont. so evolution is constant. but its not an argument, right? how to fing arguments when i only prove it.. analytically, i guess it called that (this is indirectly related to biology, im...
View full post »

Similar threads

Isotopic mass, or maybe just a silly math question
Replies
7
Views
4K
Chemistry Calculate fraction of relative molecular mass
Replies
2
Views
4K
Chemistry - Why does Bromine-80 not occur in nature?
Replies
1
Views
4K
What Is the Atomic Mass of Element A with Given Isotopes and Abundances?
Replies
1
Views
2K
Bromine Isotopes: Mass, Atomic Mass & Percent Abundance
Replies
2
Views
7K
Percent Abundance of Br-81 in Bromine
Replies
2
Views
52K
Finding mass based on amu and % abundance
Replies
2
Views
14K
Calculate % Natural Abundance of Carbon-13
Replies
2
Views
3K
Percent composition of Silver (two naturally occurring isotopes)
Replies
1
Views
2K
Easy percentage prob (for pro) hahah
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top