Molar mass vs. Molecular Weight

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anjali41
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Joined: Fri Aug 09, 2019 12:15 am

Molar mass vs. Molecular Weight

Postby anjali41 » Wed Oct 02, 2019 2:08 pm

I was wondering what the difference between molar mass and molecular weight is. How would you calculate each one?

Isha_Maniyar_Dis2E
Posts: 110
Joined: Thu Jul 11, 2019 12:16 am

Re: Molar mass vs. Molecular Weight

Postby Isha_Maniyar_Dis2E » Wed Oct 02, 2019 2:15 pm

I think molar mass is the mass of one MOLE of a molecule, while molecular weight is the mass of the molecule itself. To find molecular weight, you just find the molecular formula, multiply the atomic mass of each element by how many atoms of that element are present, and add them all together. I believe the unit for molecular weight is just amu? Hope this helped!

Lauren Haight 1E
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Re: Molar mass vs. Molecular Weight

Postby Lauren Haight 1E » Wed Oct 02, 2019 2:19 pm

The textbook defines molecular weight as the numerical value of the molar mass of a molecular compound. It defines molar mass three ways: The mass per mole of atoms of an element.(2) The mass per mole of molecules of a molecular compound. (3) The mass per mole of formula units of an ionic compound. So, what I am gathering from the textbook is that molar mass contributes to the molecular weight of a molecular compound. If we look closely, it almost looks like the second definition for molar mass is nearly the same as the textbook definition for molecular weight.

Cynthia Gong 1L
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Re: Molar mass vs. Molecular Weight

Postby Cynthia Gong 1L » Wed Oct 02, 2019 2:21 pm

^^ That is correct! We can use water as an example. For instance, water is made of hydrogen and oxygen. Hydrogen has a molar mass of 1.0079g while oxygen has a molar mass of 15.999. The values of molar mass are found from the periodic table. Meanwhile, water is a molecule made up of oxygen and hydrogen atoms. To find the molecular weight of water, H20, we would multiple the molar mass of hydrogen by 2 (2*1.0079) and then add the molar mass of oxygen to the sum (2*1.0079 + 15.99). The total will be the molecular weight of water, which is around 18.02g.

Haley Fredricks 1B
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Re: Molar mass vs. Molecular Weight

Postby Haley Fredricks 1B » Wed Oct 02, 2019 2:22 pm

I have a hard time discerning these two terms as well, but what I have gathered is that the molar mass is the mass per mole of particles, and it is measured in g/mol. This is found using the atomic weight of the constituent elements. The molecular weight is in atomic mass units (amu) and is found using the atomic mass of the constituent elements based on the number of protons and neutrons they have.

chrischyu4a
Posts: 52
Joined: Thu Jul 25, 2019 12:16 am

Re: Molar mass vs. Molecular Weight

Postby chrischyu4a » Fri Oct 04, 2019 4:58 pm

Molecular weight is basically the mass of one molecule. Molar mass would be the mass of a mole of a molecule.


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