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Homework Help: Hess's Law Calculations (Enthalpy)

  1. Nov 5, 2011 #1
    We studied the reactions NH4Cl(aq) → NH4(aq) + Cl (aq) and NH3(aq) + HCL (aq) → NH4Cl(aq) in lab today, and part of our assignment was to give the formation reaction by first calculating the neutralization part ΔH of our lab and the solution reaction part ΔH of our lab.

    We were given this:

    1/2N2(g) +3/2H2(g) → NH3(g) -45.77kj
    1/2H2(g)+ 1/2Cl2(g) → HCl (g) -92.31kj
    NH3(g) → NH3(aq. 1.50M) -35.40kj
    HCl(g) → HCl(aq, 1.50M) -72.84 kj

    And were asked to add the reactions we did in class to them. Then we were asked for Neutralization reaction ΔH and Solution reaction ΔH. After we found this we were asked for Formation reaction ΔH.

    My attempt at a solution:

    My lab partner did everything with the professor while I was cleaning up from the actual experiment, and they went to the office and since lab went over time I had to rush to get to work, so whatever was done I didn't get to see. So I'm trying to work through this on my own until my professor e-mails me back!

    I have done several Hess's Law problems in the past, but was never as confused by the wording of the question as I am now. If someone could just figure that out, I would appreciate it so much!
  2. jcsd
  3. Nov 5, 2011 #2


    User Avatar

    Staff: Mentor

    Probably the best starting point is to write reaction equations for both processes in question.
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