TPRH Chem P4, Q5 (page# 5)

[cartman1980]

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Unable to figure out something very basic. Question states that during a fusion reaction 2.2x10-31 kg of mass is unaccounted for. How much energy is generated? Mass of e = 9.1x10-31 kg, 1 amu = 931MeV, 1eV = 1.6x10-19J

Now, easy answer to this is to use einstein's e=mc^2. I tried an alternate way to solve this but the answer doesn't seem to be quite right. Just wondering why: mass lost is know, covert amu to kg, since energy of 1amu is known, energy of 1kg is known too, therefore energy of given mass diff should Be known as well.

 

[MT Headed]

The MCAT way:
(2.2*10^-31)(3*10^8)*(3*10^8) = 20*10^-15 = 2*10^-14

Your way:
(2.2*10^-31 kg)(1 amu/1.6605*10^-27 kg)(931.5 MeV/1 amu)(1*10^6 eV/1 MeV)(1.6*10^-19 J/1 eV) = 2.0*10^-14 J

They both get the same answer. I have no idea how you'd come up with the first conversion factor. I have no idea why you would want to do so much work on a timed test.

 

[cartman1980]

Thanks much...
Guess it was just a long day 🙂

And no, Wasn't trying to get the answer via a longer way... Just getting my thought process in order, and linking what I've learnt so far 🙂