Natural boron is 20 % boron-10 and 80 % boron-11, with an average atomic mass of 10.8 u.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Natural boron is boron-10 and boron-11, with an average atomic mass of . Boron-10 soaks up neutrons, so the boron in the control rods of a nuclear reactor is enriched to boron-10 and boron-11.
- Find the average atomic mass of the enriched boron.
- How much lighter is it than natural boron?
Need a reminder? The key ideaShow
The atomic mass of an element is the average of its isotopes' masses, weighted by how common each one is: . When the average is known, let be one percentage and solve for it.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) .
Step 2. (b) .
Answer: (a) . (b) lighter. The average moves towards as boron-10 becomes more common.
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