Question on radiolysis of H20 -Reply

[Keith Brown <KDB1@nrc.gov>]

>>>>>>>>>>>>>>>
OK, right up front let me say that I'm taking a university course in
Radiobiology, and the following question is part of an assignment.  I've
tried looking through a few texts on the subject, but I'm still having trouble
with what looks like a very simple problem.  I figured that RADSAFE isn't
much different from any other resource, or from asking a professor for
help - just more convenient - so here goes...

(c) Calculate the concentration of H2O2 formed.

Well, the number of moles of H2O2 formed is
3.43e18 / (6.023e12 mol^-1) = 5.70e5 mol
This is in 500 ml (0.5 liter), so the concentration is
5.70e5 mol / 0.5 liter = 1.14e6 mol/l = 1.14e6 M


Ridiculous!  At a molecular weight of about 38 g/mol, 1.14e6 mol of H2O2
molecules (the number per litre of water) would have a mass of over 40
tonnes!

Where have I gone wrong?!?!
<<<<<<<<<<<<<<<
Look up Avogadro's number again.  That should fix your problem.

Keith Brown
kdb1@nrc.gov