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Chemo Reacting Volumes Of Gasses q's

  1. Oct 15, 2003 #1
    Hi guys i need a bit of help, with a couple of questions, if possible can someone show me how to work these with the answer, thanks a lot, any help appreciated!

    1.A mixture of 2 litres of methane (Ch,4) and 4 litres of oxygen was ignited causing a combustion. Calulate the composition and volume of the gaseous mixture remaining.

    2. A mixture of 40cm^3 of hydrogen and 40cm^3 of oxygen was sparked to create an explostion. calculate the compostition and final volume of the resultant gas mixture.

    any help guys!
    cheers

    si
    :wink:

    ps, sorry i only just found there was a hwk zone bit, if a mod wants 2 move it is fair enough
     
    Last edited: Oct 15, 2003
  2. jcsd
  3. Oct 15, 2003 #2

    Monique

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    Hi SiCharlton, how are you every supposed to be able to solve this?? Is the system enclosed? What are the pressures? How much heat is released? I can't help you on this one..
     
  4. Oct 15, 2003 #3
    It's just like any other of these chemistry problems. First, figure out how many moles of material you have. Then figure out the limiting reagent. Then figure out how much product you get. The total volume after reaction will depend on the number of mole of product plus the number of moles left of the limiting reagent.

    You do know how to get moles from volume of gas and vice versa, right?
     
  5. Oct 15, 2003 #4
    chemicalsuperfreak thankyou very much helped a lot!!!
    :>:>:> all done now,
    cheers
    si
     
  6. Oct 16, 2003 #5

    Monique

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    Well, yeah, but..

    The volume of a gas depends on its temperature and under how much pressure it is.. there is nothing said about that in the question, especially.. what happens after an explosion? The volume would fill the room.

    Anyway, if it solved it for you, SiCharlton, than it is all good.
     
  7. Oct 16, 2003 #6
    If it's not stated assume STP. You can also assume it's a sealed container, a closed system, and that the final state will also be STP. Just to simplify things. You also have to assume a complete reaction resulting in a single prouct. And the latter is probable the most difficult to justify if this were a real world problem.
     
  8. Oct 16, 2003 #7

    Bystander

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    STP is not a necessary assumption; it is necessary to assume ideal gas behavior, and that reactants and products are at the same conditions of T,P. Information enough is given to determine mole ratios only.
     
    Last edited: Oct 16, 2003
  9. Oct 16, 2003 #8
    Yes, for this question. But often there are questions where the pressure and temperature do matter, and it is not given. And in these cases STP is conventionally assumed. Plus, knowing the volume of one mole of gas at STP makes for quite an easy "back of the envelope" approach to this problem.
     
  10. Oct 16, 2003 #9

    Monique

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    What was that conversion constant? 14.6 seems to stand out in my memory, am I right? I haven't used that in like 4-5 years so I could be very far off
     
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