Chemistry Question...Help!

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

  1. ipodtouchy333 macrumors 65816

    Joined:
    Nov 15, 2007
    Location:
    US
    #1
    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

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
    #2
    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

    Joined:
    Nov 15, 2007
    Location:
    US
    #3
    Wait, what is n though? I'm sorry if I sound dumb but I was absent from school, lol.
     
  4. fireshot91 macrumors 601

    fireshot91

    Joined:
    Jul 31, 2008
    Location:
    Northern VA
  5. eldy macrumors 6502

    Joined:
    Jan 30, 2009
    Location:
    The City
    #5
    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

    Joined:
    Nov 19, 2007
    Location:
    Portland, OR
    #6
    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!

    SLC
     

Share This Page