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Propane: Liquid to Gas

  1. Dec 12, 2011 #1

    I was wondering, if 1 ml of liquid propane (120 psi @ 70°F) is released into the atmosphere assume 14.696 psi (constant temperature), what will be the change in volume of what used to be 1 ml of liquid propane when changed to gas?

    From what i heard, the ratio for most gases expanded from liquid is 1:800 units.
    I got it from some fun facts website years ago. given the difference in properties of different gasses i really doubt the 1:800 ratio, so please lend me a hand if you have the time :)

    Thanks ahead of time!

    follow up question,
    what is the diffuse velocity of the gas and how long will it take? Assume the 1ml propane is contained in a cylindrical canister with an circular opening of .75" dia.
    Last edited: Dec 12, 2011
  2. jcsd
  3. Dec 13, 2011 #2
    Well, here's how I'd solve it, with fair precision:

    Propane (C3H8) is ~44.1 g/mol (you can look it up to the desired accuracy)

    A mole of most gases at Standard Temperature/Pressure (1atm, 0 C) occupies ~22.4 L

    Therefore, 1 g of propane gas @ STP occupies .508 L.

    Dividing by the density of liquid propane would give the answer for 1 cc, instead of 1 g

    You'd need to look up thermal corrections for 70F vs 32F (O C), but often these are given as density (specific gravity) charts in g/cc or kg/L, from which you could read expansion fairly directly without much calculation. The main advantage of my method is that it is easy to approximate the expansion for most gases from standard references like the CRC tables

    This online calculator gives an expansion ratio of 311, using actual values, not general principles.
  4. Dec 13, 2011 #3
    Thanks! this is really really useful :D
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