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Topic: Atomic Mass Unit  (Read 3035 times)

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Offline kevinmorales

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Atomic Mass Unit
« on: September 26, 2017, 09:38:10 PM »
Hi,
This is my first time here :)
I have a pretty weird question. It kept bugging me so I had to ask here. One atomic mass unit is equal to 1,660 538 921 × 10−27 kg, which is theoratically equal to 1/12 of the mass of the carbon 12. But if I do the equation 1/12*(6*(proton mass)+6*(neutron mass))...basically (proton mass + neutron mass)/2 = (carbon 12 mass)/12, it equals to 1.674×10^-27 kilograms.... I find it pretty strange since it's supposed to be equal to one atomic mass unit.
Thank you for your time in advance :)

Offline Borek

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Re: Atomic Mass Unit
« Reply #1 on: September 27, 2017, 02:48:02 AM »
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline Vidya

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Re: Atomic Mass Unit
« Reply #2 on: September 29, 2017, 10:23:03 AM »
Hi,
This is my first time here :)
I have a pretty weird question. It kept bugging me so I had to ask here. One atomic mass unit is equal to 1,660 538 921 × 10−27 kg, which is theoratically equal to 1/12 of the mass of the carbon 12. But if I do the equation 1/12*(6*(proton mass)+6*(neutron mass))...basically (proton mass + neutron mass)/2 = (carbon 12 mass)/12, it equals to 1.674×10^-27 kilograms.... I find it pretty strange since it's supposed to be equal to one atomic mass unit.
Thank you for your time in advance :)
You must have heard about mass defect ...?

Offline Enthalpy

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Re: Atomic Mass Unit
« Reply #3 on: October 10, 2017, 06:43:29 AM »
The biggest error here is that you've forgotten the electron mass.

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