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Homework Help: Gas Stoichiometry

  1. Nov 7, 2009 #1
    1. The problem statement, all variables and given/known data

    Calcium carbide reacts with water to produce acetylene gas: CaC2 (s) + 2H2O (l) >> Ca(OH)2 (aq) + C2H2 (g). What volume of wet acetylene is collected at 25C and 715 torr when 5.20g CaC2 is reacted with an excess of water? (Vapor pressure of water at 25C = 23.8 torr)

    2. Relevant equations


    3. The attempt at a solution

    I found the moles of "dry" C2H2 (.0811 mol). However, I'm not very sure where vapor pressure and the "wet" comes in...
  2. jcsd
  3. Nov 7, 2009 #2
    What is the total pressure, Ptotal, of the system? What are the partial pressures?
  4. Nov 7, 2009 #3
    Ptotal=715 torr
    PH2O=23.8 torr
    PC2H2=691.2 torr

    I'm still not exactly sure how all of these fit in....
  5. Nov 8, 2009 #4


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    Staff: Mentor

    What is volume of acetylene calculated using its partial pressure?

  6. Nov 18, 2009 #5
    Using the equation PV = nRT, do you recall what P, V, n, R and T stand for? They also need to be in certain units. This may or may not require converting. Do you still need help for this?
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