Chemistry Question...Help!

Discussion in 'Community Discussion' started by ipodtouchy333, Mar 1, 2009.

  1. ipodtouchy333 macrumors 65816

    Nov 15, 2007
    Ok, I'm doing some chem homework and trying to figure out this question. Using the ideal gas law (pV=nRT): What volume would be occupied by 100 g of oxygen gas at a pressure of 1.5 atm and a temperature of 25 degrees C? Thanks!
  2. alphaod macrumors Core


    Feb 9, 2008
    n is number of moles
    R is a constant (ideal gas constant)
    T you have (temp in Kelvin)
    p you have

    So solve it.
  3. ipodtouchy333 thread starter macrumors 65816

    Nov 15, 2007
    Wait, what is n though? I'm sorry if I sound dumb but I was absent from school, lol.
  4. fireshot91 macrumors 601


    Jul 31, 2008
    Northern VA
  5. eldy macrumors 6502

    Jan 30, 2009
    The City
    you have to convert 100 g of oxygen number into number of moles of oxygen. hint: use the periodic table of elements to get the weight of one mole of oxygen.
  6. SLC Flyfishing Suspended

    SLC Flyfishing

    Nov 19, 2007
    Portland, OR
    n is the number of moles of the product you're working with, in this case oxygen.

    If you take a look at the periodic table you'll note that Oxygen's molar mass is 15.9994 g/mol meaning that 15.9994 grams of oxygen is equivalent to one mol of oxygen. A mole incase you aren't familiar with the term is an atom or molecule count, it represents 6.022x10^23 particles (or any item really).

    So what you do is take your 100 g of oxygen and divide it by the 15.9994 grams that constitute each mol of Oxygen and that gives you your # of moles. In this case it's (100g)/(15.9994g/mol)=6.25 mol

    You then take that mol amount and use it as your n figure in the PV=nRT equation. Isolating for the variable you're interested in, which for this question is Volume.

    So: V=(nRT/P)

    plug in your values and you have
    V=((6.25mol)(0.082 057 46(Lxatm/molxK)(298K))/(1.5atm)

    All units save the litres cancel out and you're left with a volume of 229.248 Litres.

    I've done your homework for you, but I've outlined just how it's done so make sure you learn it now!


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