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Gas laws corrections

  1. Nov 4, 2005 #1

    DB

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    could u guys tell if im right with these:
    1)
    a) calculate the volume occupied by 6.5 g of Nitrogen gas @ STP

    [tex]\frac{1_{mol}}{28g_{N_2}}=\frac{x_{mol}}{6.5g}[/tex]

    [tex]x\sim0.23[/tex]

    [tex]\frac{101.3*V}{273*0.23}=8.31[/tex]

    so i got that 6.5 grams of N_2 is ~ 0.23 mol so using the ideal gas law i solved for V getting 5.15 L

    b) calculate the volume occupied by this mass of gas at -40.0 C and 65.0 kPa

    [tex]\frac{65*V}{233*0.23}=8.31[/tex]

    so i did the same thing as "a" except filled in those values of temperature(kelvin) and pressure, i got 6.9 L
    2)
    this one im not so sure about:
    what is the molar mass of a gas if 375 cm^3 have mass 0.800 g at 85 C and 100.7 kPa?
    using the ideal gas law i did:

    [tex]\frac{100.7*0.375}{358*n}=8.31[/tex]

    [tex]n\sim ~ 0.013 mol[/tex]

    then i divided 0.800g by 0.013 mol and got ~ 61.5 grams molar mass
    is that right?
    thanks in advance
     
    Last edited: Nov 4, 2005
  2. jcsd
  3. Nov 5, 2005 #2

    GCT

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    you're using the wrong units, review your text or use common sense and use the correct units, remember standard temperature is 25C
     
  4. Nov 5, 2005 #3

    DB

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    no you're thinking standard AMBIENT temp and pressure, these problems deal with STP, being 0C and 101.3 kPa
     
  5. Nov 5, 2005 #4

    GCT

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    alright, check your answers with the that obtained by using the conversion factor 1mole/22.4L, part a) seems right, the third one seems fine by me
     
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