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Homework Help: - Mole and Avogadro's Number -

  1. Nov 19, 2005 #1
    2.95 mol Ba(OH)4 to atoms. (I think I wrote this problem wrong. It might be (OH)2 instead).
    I'm confused >.< Do I:
    1) multiply 2.95 mol by 6.02 x 10^23 atoms or
    2) multiply 2.95 mol x 6.02 x 10^23 molcules x 9 atoms.
    or is it something else?

    Also, how do I do these?
    Calculate the mass of 3.01 x 10^23 formula units (ions) of Strontium hydroxide.
    Find the number of atoms in 16.0g of sulfur

    Please help if you can. ~____~
    Last edited: Nov 19, 2005
  2. jcsd
  3. Nov 19, 2005 #2


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    moles is amount of particals. When this compound is broken down it is split into 1Ba and 4(OH) [according to you].

    moles * 6.02E23= number of particals
    (Number of particles)*(Number of particles the molecule can decompose to)=number of ions of that particular particle.
  4. Nov 20, 2005 #3
    hence no. of molecules=2.95*6.023*10^23
    hence no. of atoms= no. of molecules*no. of atoms per molecule(9 in your case, though it is Ba (OH)2, i.e. 5):smile:
    Strontium hydroxide is Sr (OH)2
    hence no. of formula units= no. of atoms
    hence mass = (molarmass/avogadro's no.)*no. of units
    same for next.
    refer University Chemistry by Bruce Mahan for details.
  5. Nov 20, 2005 #4


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    Homework Helper

    if they're asking for the atoms of Ba(OH)2 and not its constituent ions, then you would simply solve this by factor labeling

    2.95mol Ba(OH)2(6.022x10^23 molecules Ba(OH)2/1mol Ba(OH)2) =?, you should verify that the units cancel out during such processes
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