Quantum Jim's Journal: Interesting Google Calculator Problems (updated)

Updated: see bottom of post.

I should know this, but I forgot. I asked google for the mass of hydrogen, and it told me the answer is 1.00794 amu according to this web page. Then I asked google to compute the mass of proton + mass of electron in amu, which it says is 1.00782549 atomic mass units. Where did the extra .00121167351 amu (2.01202991 * 10^-30 kg) mass come from? The binding energy of hydrogen?

P.S. I got moderator points again, even though I didn't metamoderate since my last journal entry. /. want's me to waste time, doesn't she? ;-)

Update:

Thanks for the suggestions: they were very insightful. According to the Wikipeida, deuterium exists in .015% of natural hydrogen, while the rest don't have a large enough lifetime to affect the natural abundance ratios. I had Google calculate (1-.00015) * (proton mass + electron mass) + .00015 * (1.009132 amu + proton mass + electron mass) in amu (odd that Google doesn't have the neutron mass in the calculator). I could have calculated proton mass + electron mass + .00015 * 1.009132 amu in amu for the same result.

Now Google thinks the mass of naturally occuring hydrogen is 1.00797686 amu. Where did the extra .00004 amu in Google's calculation come from? That's about 2.5 times the binding energy (13.6 keV), so I don't think that accounts for it. Puzzling, I think. It has been too long since chemistry class. ;-)

Hydrogen isn't *always* a 0-neutron element...

[PugMajere]

Perhaps the rates of naturally occuring deuterium and tritium are used to figure the average mass?

Re:Hydrogen isn't *always* a 0-neutron element...

[Geoffreyerffoeg]

I'm pretty sure you're right. A google search for [mass of protium]* yields several pages giving 1.007825, or 1p + 1e.

(Actually, try [mass of protium -"twice the"], since there are a bunch of pages describing the mass of deuterium vs. that of protium)

There is some binding energy, isn't there?

[sam_handelman]

Convert the energy yield form an electron at d= infinity moving into energy level 0 of the proton and see what mass difference you get.

Actually, that doesn't even make sense, since that lowers the mass some excruciatingly tiny amount. It must be the natural abundance of deuterium.