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Homework Help: Diploma Help!

  1. Jan 7, 2005 #1
    In my Chemistry class we are doing some old diploma review questions in order to prepare for this year's Chemistry diploma. I have answered almost all of the questions.

    It says:

    The above apparatus (I'll explain the diagram later) was used to determine experimentally the molar enthalpy of the combustionm of candle wax, C25H52(s) (I don't know how to do subscripts).


    a. List all the measurements that must be taken in order to determine the molar enthalpy of combustion.

    - I finished this part....this was pretty easy.

    b. Write a mathematical equation that uses the data collected and that will allow you to detrmine the molar heat of combustion. Label each of the mathematical variables used in the equation.

    - I finished this part too....not hard at all.

    c. Suggest two improvements to the experimental design.

    - I've always been really bad at answering these type of questions, maybe because I'm not a conceptual person....

    The diagram is just a picture of a calorimeter made out of a solid copper container. The container has a lid on with a thermomenter sticking out of it. Inside the container is liquid water, and the container is being heated with the wax candle. I'm not sure how I could improve the experimental design....
  2. jcsd
  3. Jan 7, 2005 #2


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    - What is ACTUALLY being heated? The water, the copper container, the air inside the container, the atmosphere, even the thermometer... each part of the system is warming up, so to do an accurate calculation, the warming of each part must be taken into consideration, even the candle wax itself as it melts.

    So how could we ONLY test for the heat generated by the burning candle wax? Note that even the nitrogen in the air supporting combustion affects the overall calculation.
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