Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The concept of mole

  1. May 23, 2012 #1
    i need to get the hang of the mole concept that , 1.008 g of hydrogen constitutes 1 mole atom, whereas 12g of carbon constitute that 1 mole atom! does it mean that these amounts for H & C contains the Avogadro number of atoms??
    does it imply the hydrogen is more denser (or heavier or something crucial) than the carbon as it needs to be only 1 gm of it to be 1 mole?? why does this difference in mole amount (of grams ) happen??
     
  2. jcsd
  3. May 23, 2012 #2

    phyzguy

    User Avatar
    Science Advisor

    A mole is just a number of things, like a dozen. A mole of carbon atoms weighs more than a mole of hydrogen atoms because each carbon atom weighs more than each hydrogen atom. Just like a dozen bowling balls weighs more than a dozen ping-pong balls.
     
  4. May 23, 2012 #3

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    welcome to pf!

    hi cooper607! welcome to pf! :smile:
    … to be precise (almost), 6.022142 1023 things :wink:

    (see http://en.wikipedia.org/wiki/Mole_(unit [Broken]))

    if you go into the garden and find 602,214,200,000,000,000,000,000 moles, that's a mole of moles! :biggrin:
     
    Last edited by a moderator: May 6, 2017
  5. May 23, 2012 #4

    Philip Wood

    User Avatar
    Gold Member

    Why is NA, the Avogadro number, chosen to be [itex]6.02\times10^{23}[/itex] (to 3 sf)?

    Because this number is the number of atomic mass units (u) in 1 gram.

    That is [itex]1 \text{g} = 6.02\times10^{23} \text{u} = N_A \text{u}[/itex]

    So, because the mass of a C12 atom is 12 u, the mass of a mole of them (Avogadro's number of them) will be [itex]N_A \times 12 \text{u} = 12 \times N_A \text{u} = 12 \text{g}.[/itex]

    [Note:in the SI, the Avogadro constant is defined to be a quantity with units, namely
    Avogadro constant = [itex]6.02\times10^{23} \text{mol}^{-1}.[/itex]]
     
  6. May 23, 2012 #5

    Borek

    User Avatar

    Staff: Mentor

    No, the only thing it is related to is the mass of a single atom (molecule). Light atom (molecule) - low molar mass, heavy atom (molecule) - large molar mass.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: The concept of mole
  1. Mole Concept (Replies: 22)

  2. Mole ratios (Replies: 1)

  3. Mole Concept (Replies: 1)

  4. Help with moles (Replies: 5)

Loading...