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Homework Help: Mass Balance Qn

  1. Nov 13, 2016 #1
    • Member advised to use the homework template for posts in the homework sections of PF.
    Acetylene (C2H2) is reacted with excess O2 in a container. After complete reaction, the volume of the gaseous mixture of the combustion products is 300ft3 at 60C and 10mmHg gauge pressure. P(atm) is 735mmHg. The relative humidity if the product gas is 100% with no condensed water present. Calculate the moles of acetylene and oxygen in the original mixture.

    GIven: Saturated vapour pressure of water at 60C is 150mmHg

    Pls help!!

    I dont really know how to continue
  2. jcsd
  3. Nov 13, 2016 #2
    What is the balanced chemical reaction equation for the reaction of acetylene with oxygen? How many moles of gases are present in the final state of the system? What are the gases present in the final state of the system? How many moles of water are present in the final state of the system?
  4. Nov 13, 2016 #3
    The equation is C2H2 + 5/2 O2 -> 2CO2 + H2O
    Gases in final state would be O2, CO2, and H2O.
    I can find the mole fraction of H20 through Raoults law but i dont really know how to continue from there
  5. Nov 13, 2016 #4
    OK. How many moles of water are there? How many moles of C2H2 reacted to produce this amount of water?
  6. Nov 13, 2016 #5
    Hmmm ok correct me if im wrong.
    Mole fraction (h2o) = 150/745 = 0.20134
    use this to find the moles of h2o using PV= nRT, assuming ideal gas.

    use n to find moles of c2h2 and o2 in original mixture.
  7. Nov 13, 2016 #6

    First find total number of moles. Then get moles of h20. From this get original moles of c2h2. From this get moles of co2. From this info, get original moles of o2.
  8. Nov 13, 2016 #7
    Alright!! thnks!!!
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