Molar Mass

[Natalie_Martinez_1I]

How do you calculate the molar mass of substance?

[sylvie_1D]

You use the periodic table and look up the element's atomic mass. If you have a compound like h2o, you add up the atomic masses of 2(h) and 1 (o) to get the molar mass.

[Isobel Tweedt 1E]

Can someone please clarify when we use molar mass versus atomic mass?

[april_bussey_1C]

Atomic mass is measured via mass spectrometry. Molar mass is computed from the atomic weight. There are no units of measurement for atomic masses because these are relative masses meaning these are “unitless.” So the atomic mass is measured by calculating the mass of protons and neutrons. Whereas the Molar Mass is the grams per moles of a specific element. (or a specific compound by adding the molar mass of each element in the compound). The molar mass had units (g/moles) and the atomic mass is unitless.

[kimberlysanchez-1E]

april is correct

[AlyssaRivera]

Atomic mass is the mass of an individual atom but molar mass is the mass of one mole of an atom.

[juliaschreib1A]

The correct units for molar mass is grams/mole, so you calculate the grams and that will be equal to one mole.

[Chem_Mod]

The atomic mass does have units of mass. It can be in terms of "atomic mass unit" or even "kg" since this term refers to the mass of a single atom.

Unless we are talking atomic scale reactions (few tens and hundreds of atoms), we typically use molar mass since most everyday reactions concern with large quantities (moles) of chemicals in a reaction.

[Elijah E 1C]

It's also important to understand that Atomic mass is "unitless", while molar mass is grams/mol.

[Jennifer 1G]

I believe you add up all the weights of the elements. For example, in H20, you would multiply the weight of Hydrogen times two and add the weight of oxygen. I just noticed someone used H20 as an example previously, but this applies for other examples.