Percent Abundance of Br-81 in Bromine

In summary, the percent abundance of Br-81 in bromine is approximately 49.31%. It is determined through experiments such as mass spectrometry or nuclear magnetic resonance (NMR) spectroscopy. Knowing this percentage is important for understanding the element's properties. It can also vary slightly in different sources and does not change over time, but the total amount of Br-81 and Br-79 can change due to radioactive decay.
  • #1
mugzieee
77
0
Br consists of Br-79 and Br-81. The atomic mass of Br is 79.9. Find the % of Br-81 in bromine.
 
Physics news on Phys.org
  • #2
Do you know a formula for calculating the atomic mass from percentages of different isotopes?

Atomic mass is equal, in this case, to:

[(Br-79 percentage abundance/100) x 79] + [(Br-81 percentage abundance/100) x 81]


Because you know the atomic mass and not the abundances, let percentage abundance of Br-81 be X. Then you can write an expression for the percentage abundance of Br-79, and so can calculate the value you need.
 
  • #3


The percent abundance of Br-81 in bromine can be calculated using the following formula:

% abundance of Br-81 = (atomic mass of Br - atomic mass of Br-79) / (atomic mass of Br-81 - atomic mass of Br-79) * 100

Plugging in the values given in the question, we get:

% abundance of Br-81 = (79.9 - 79) / (81 - 79) * 100
% abundance of Br-81 = 0.9 / 2 * 100
% abundance of Br-81 = 0.45 * 100
% abundance of Br-81 = 45%

Therefore, the percent abundance of Br-81 in bromine is 45%. This means that out of every 100 atoms of bromine, 45 of them will be Br-81 and the remaining 55 will be Br-79.
 

1. What is the percent abundance of Br-81 in bromine?

The percent abundance of Br-81 in bromine is approximately 49.31%. This means that out of all the bromine atoms in a sample, 49.31% will be Br-81 and the remaining 50.69% will be Br-79.

2. How is the percent abundance of Br-81 determined?

The percent abundance of Br-81 is determined through experiments such as mass spectrometry or nuclear magnetic resonance (NMR) spectroscopy. These techniques can separate and identify different isotopes of an element based on their mass-to-charge ratio or nuclear spin.

3. Why is it important to know the percent abundance of Br-81 in bromine?

Knowing the percent abundance of Br-81 in bromine is important for understanding the chemical and physical properties of the element. Isotopes can have different reactivity and stability, which can impact their role in chemical reactions and biological processes.

4. Does the percent abundance of Br-81 vary in different sources of bromine?

Yes, the percent abundance of Br-81 can vary slightly in different sources of bromine. This is because different sources can have different isotopic compositions due to natural processes such as radioactive decay or fractionation.

5. Can the percent abundance of Br-81 change over time?

No, the percent abundance of Br-81 is a constant value for a given sample of bromine. However, over time, the total amount of Br-81 and Br-79 can change due to radioactive decay. This can affect the overall percent abundance of Br-81 in a sample.

Similar threads

  • Introductory Physics Homework Help
Replies
5
Views
4K
  • Biology and Chemistry Homework Help
Replies
2
Views
2K
Replies
3
Views
3K
  • Biology and Chemistry Homework Help
Replies
7
Views
4K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Biology and Chemistry Homework Help
Replies
2
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
12
Views
4K
  • Biology and Chemistry Homework Help
Replies
2
Views
7K
Back
Top