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If molar mass and molecular mass are calculated the same way why do we need both?

  1. Oct 12, 2012 #1
    Is it just so chemistry is extra confusing to students? I don't understand...
     
  2. jcsd
  3. Oct 12, 2012 #2
    Re: If molar mass and molecular mass are calculated the same way.. why do we need bot

    Ugh...no...it is not the same.
    Molecular mass is the average quantity of nucleons (protons + neutrons) in a single molecule of the compound. It is NOT measured in grams, but in gram/mole. This means, for example, water, H2O, has a molecular mass of 18g/mol, because the average hydrogen has 1 proton and the average oxygen has 16 nucleons (1*2+16=18).
    Thus, 18 grams of water are 1 mole.
    Any pair of scales measures weight, not molecular mass, so you forcefully need to know the molecular mass and the required weight to get the quantity of moles you need.

    And chemistry is not confusing if you get into it. Try to have a friend explain you, I am aware some teachers are terrible.
     
  4. Oct 13, 2012 #3
    Re: If molar mass and molecular mass are calculated the same way.. why do we need bot

    Ugh omg you didn't explain what molar mass was? *eyeroll*

    And yes my teacher doesn't speak good english so its hard to understand, and I don't have friends so my bad if this question is SOOOO beneath your intelligence level.
     
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