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NS FL#6 C/P Q42

Posted: Tue May 14, 2019 7:29 am
by sdaswani
Hi! I wanted to make sure my understanding of the solution to this problem is correct. I understand how we get 35g of FDG that underwent the radioactive decay. From here, 35g = 35g / 181g per mol to get the number of moles of FDG that underwent decay. Moving forward, is it true that each particle of the total number of moles of FDG, underwent the decay and released 2 gamma rays of 511 keV, each?

Why do we think of decay per particle instead of per mole?

Thanks!
-Saakshi

Re: NS FL#6 C/P Q42

Posted: Tue May 14, 2019 8:40 am
by NS_Tutor_Will
Yes, your reasoning is correct! We don't necessarily have to think of decay as a per particle situation, we are perfectly within our rights to think of it on a molar scale (after all, moles just refers to a whole bunch of individual particles so a mole should act pretty much the same as a particle, just on a larger scale!).

In this case, since we're given answer choices in keV and since we're told about gamma rays in terms of particles ("2 gamma rays are emitted, each with 511 keV"), it makes the most sense to think on the scale of particle for the sake of efficiency.

Thanks for the question!

Re: NS FL#6 C/P Q42

Posted: Tue May 14, 2019 11:46 am
by sdaswani
Got it, thanks for the help!!