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Homework Help: Heat of formation of nh4cl

  1. Feb 12, 2007 #1

    mullen1120

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    1. The problem statement, all variables and given/known data
    i did a lab calorimeter lab with 50ml 1.51M nh3 and 50ml 1.59M hcl yeilding nh4cl (aq)
    the deltaT was 8.6 degC
    second part is 100ml of h2o and 4.082g nh4cl
    deltaT was -2.8 degC



    2. Relevant equations
    how do i find deltaH per mole for each reaction?


    3. The attempt at a solution
     
    mullen1120, Feb 12, 2007
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  3. Feb 12, 2007 #2

    chemisttree

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    Give us your try at the answer.....

    Hint: Write out the reactions for the first part and the second part. What form was the ammonia? Was it aqueous? How should that be written?
     
    chemisttree, Feb 12, 2007
  4. Feb 12, 2007 #3

    mullen1120

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    its nh3(aq) + hclz(aq) = nh4cl(aq)
    and nh4cl(s) = nh4cl(aq)

    but where do i go from there?
     
    mullen1120, Feb 12, 2007
  5. Feb 13, 2007 #4

    chemisttree

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    NH3 in water is NH4+ OH-
    HCl in water is H3O+ Cl-

    one of the two reactions is:

    NH4+(aq) + Cl-(aq) ----> NH4Cl(aq)

    Can you determine the other reaction?

    You will need the heat capacity of the ammonium chloride solution. Can you determine what the concentration will be?
    Alternatively, you could assume the heat capacity of pure water, but it won't be an exact solution. Can you think of why you need to obtain the heat capacity?
     
    chemisttree, Feb 13, 2007
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