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### Problem 107

00:22
University of Miami

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Problem 106

Relative Abundances Magnesium constitutes about 2$\%$
of Earth's crust and has three naturally occurring isotopes. Suppose you analyze a mineral and determine
that it contains the three isotopes in the following proportions: Mg- 24 (abundance = $79 \% ), \mathrm{Mg}-25$ (abundance $=10 \% ),$ and $\mathrm{Mg}-26$ (abundance = 11 $\%$ ). If your
friend analyzes a different mineral containing magnesium, do you expect her to obtain the same relative
abundances for each magnesium isotope? Explain your
reasoning.

Yes.

## Discussion

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## Video Transcript

you know, work on problem 106 from chapter four in this problem, Um, we're talking about magnesium and it's London's, we're told in about 2% of the earth's crust is magnesium and there are three naturally occurring isotopes. And so if we interlace mineral and we see that it contains three s it hopes of magnesium with magnesium 24 an abundance of 79%. What an abundance of 10% for maybe some 25. And for my niece from 26 you have an abundance of 11%. So if someone else friend were to analyze another part of the earth, a different mineral continue magnesium. Would we expect them to obtain the same abundance for each magnesium? So here we're talking about ah, different percentages isotopes. And the answer is that yes, it should be the same. Now, why is this? This is because, um when isotopes are naturally occurring, it's largely independent environment. Um, the ice Ato. There's no particular reason in the environment why we should change the natural abundance of any particular isotope. We could do this lab changing the uh percent abundance of a particular isotope. But in nature percent, abundance largely remains unchanged. So the abundance the relative abundance of these magnesium isotopes should be the same