Five mole of calcium carbide is combined with 10 mol of liquid water in a closed, rigid, high-pressure vessel of volume 750 mL. Acetylene gas is produced by the reaction:
CaC2(s) + 2 H2O(l) => C2H2(g) + Ca(OH)2(s)
Initial conditions are 25oC and 1 bar, and the reaction goes to completion. For a final temperature of 125oC, determine
a.) The final pressure
b.) The heat transferred
At 125oC, the molar volume of Ca(OH)2 is 33.0 mL/mol. Ignore the effect of any gas present in the vessel initially.
2 comments:
I've correctly calculated both P2 as 204 bar and Hr as -6.3kj/mol. I also calculated Hrxn, and H required to heat up the products from 25-125 degrees C. When I sum these together I get -619.7 kj/mol. Is there an enthalpy I'm not counting? I also considered that the enthalpy change at constant T from P=1 to P=204 bar is zero, and the Hr of the product gas at 1bar and 25 C is .05 kj/mol, indicating that the gas is essentially ideal at those conditions.
spoonman 4:48 PM
Your P2 is pretty much correct and your Hr is right on.
Did you take into account the energy required to heat up the Ca(OH)2 (s) ? You can lookup the Cp of this solid in the textbook. I think this is the issue.
Yes, I did not calculate Hr for the feed gas because I assumed it was ideal at 35C and 1 bar. Your results confirm my assumption.
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