Molar Mass vs. Atomic Weight

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Yen Ho Chou 1D
Posts: 28
Joined: Wed Feb 27, 2019 12:16 am

Molar Mass vs. Atomic Weight

Postby Yen Ho Chou 1D » Wed Jun 26, 2019 10:23 pm

Can someone explain to me the difference between molar mass and atomic weight. When should I use them?

Leah farhadi 1F
Posts: 36
Joined: Mon Jun 17, 2019 7:23 am

Re: Molar Mass vs. Atomic Weight

Postby Leah farhadi 1F » Thu Jun 27, 2019 12:28 am

I think they are relatively the same, but atomic mass is related to the element itself (found on the periodic table, i.e carbon, oxygen, hydrogen). But molecular mass takes into account that there are multiple elements (atomic masses) that make up the compound (i.e H2O or CO2).

Haorui Li 1A
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Joined: Mon Jun 17, 2019 7:23 am

Re: Molar Mass vs. Atomic Weight

Postby Haorui Li 1A » Thu Jun 27, 2019 11:17 am

The unit for atomic mass is in amu, however, the unit for molar mass is g/mol.

Brian Kwak 1D
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Joined: Fri Sep 28, 2018 12:17 am

Re: Molar Mass vs. Atomic Weight

Postby Brian Kwak 1D » Fri Jun 28, 2019 10:47 am

Atomic mass is related to a single element while molar mass is the total mass of the compound. So you would need to sum the atomic masses of the compound(molecular formula) to get the molar mass of the compound. It’s important to note that atomic mass and molar mass is g/mol.

jlinwashington1B
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Joined: Fri Sep 28, 2018 12:22 am

Re: Molar Mass vs. Atomic Weight

Postby jlinwashington1B » Thu Jul 04, 2019 12:53 pm

Molar mass is the sum of the atomic mass (the elements listed on the periodic table).

Karina Vasquez 1D
Posts: 35
Joined: Fri Mar 01, 2019 12:15 am

Re: Molar Mass vs. Atomic Weight

Postby Karina Vasquez 1D » Sat Jul 06, 2019 2:12 pm

From what I know molar mass and atomic weight are numerically equivalent, although they have different units. So the unit for atomic weight is amu and molar mass would be in g/mol. Hope that helped!

Daniel Kim 1D
Posts: 38
Joined: Wed Oct 03, 2018 12:17 am

Re: Molar Mass vs. Atomic Weight

Postby Daniel Kim 1D » Sat Jul 06, 2019 6:05 pm

They are pretty much the same thing. Molar mass is to find the mass for one mole. Atomic weight is the mass in grams, I’m pretty sure!

Chem_Mod
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Re: Molar Mass vs. Atomic Weight

Postby Chem_Mod » Sun Jul 07, 2019 10:49 am

Atomic mass is the mass of an atom. A single atom has a set number of protons and neutrons, so the mass is unequivocal (won't change) and is the sum of the number of protons and neutrons in the atom. Electrons contribute so little mass that they aren't counted.

Atomic weight is a weighted average of the mass of all the atoms of an element, based on the abundance of isotopes. The atomic weight can change because it depends on our understanding of how much of each isotope of an element exists.

Both atomic mass and atomic weight rely on the atomic mass unit (amu), which is 1/12th the mass of an atom of carbon-12 in its ground state.

Can Atomic Mass and Atomic Weight Ever Be the Same?

If you find an element that exists as only one isotope, then the atomic mass and the atomic weight will be the same. Atomic mass and atomic weight may equal each other whenever you are working with a single isotope of an element, too. In this case, you use the atomic mass in calculations rather than the atomic weight of the element from the periodic table.


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