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Topic: Difference between amu and grams?  (Read 3050 times)

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Offline derrickla1

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Difference between amu and grams?
« on: April 12, 2017, 08:43:39 AM »
Hello.

I am reading up on high school chemistry curricula during my holidays to compensate for the two-year-loss from not studying in class heretofore. I searched on the internet regarding this topic and have yet to come to a clear idea regarding the topic.

What is the difference between amu and grams?

From my understanding, an amu is 1/12th of 12 grams of carbon-12 atom. And a gram is amu, but unlike amu, it calculates the atomic weight of 6.022e23 atoms.

Am I wrong here? The book issued by the curricula development center has not defined any of these terms whatsoever, only mentioning the value of Avogadro's number and the terms without explaining the relationship in between. The two reference books and online resources I referred to led me to the conclusion above.

Thanks for your time.

Offline mjc123

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Re: Difference between amu and grams?
« Reply #1 on: April 12, 2017, 11:31:56 AM »
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an amu is 1/12th of 12 grams of carbon-12 atom.
No. 1/12 of 12 grams is 1 gram. An amu is a mass unit equal to 1/12 the mass of ONE carbon-12 atom. Its value is 1.66056 x 10-27 kg.
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And a gram is amu, but unlike amu
How is it amu if it is unlike amu?
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it calculates the atomic weight of 6.022e23 atoms
An atom has an atomic weight. Do you mean "the weight of 6.022e23 atoms"? That is wrong unless the atomic weight is exactly 1.
The mass of Avogadro's number of (identical) atoms is equal to the atomic weight in grams. Thus e.g. NA atoms of carbon-12 weigh exactly 12 g.
See https://en.wikipedia.org/wiki/Relative_atomic_mass (the more correct term for "atomic weight")

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