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Homework Help: Why the experimental error for CaOH is larger than MgO?

  1. Jan 7, 2016 #1
    1. The problem statement, all variables and given/known data

    I did a lab on the experimental application of Hess's law. There were two experiments where a substance in a solution was dissolved and the temperatures were recorded. Then the standard heat of formation for the substance was calculated. The first experiment used MgO and HCL and the second experiment used CaOH and water.

    A question in the lab was :

    "Explain why the experimental error for the calcium error for the calcium hydroxide is much larger than magnesium oxide.In this experiment, it was assumed that the calcium hydroxide formed was in the solid form, whereas some of the solid that formed must have dissolved. Using this information, determine by calculation how much of an impact the above assumption had on the final experimental value for the heat of formation of calcium hydroxide."

    I don't quite understand what calculation to do here, or an explanation for this either. It cannot be the percentage error as i have already calculated those in an earlier question. Any help on this question would be very much appreciated, thank you.
  2. jcsd
  3. Jan 7, 2016 #2


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    Science Advisor
    Homework Helper
    Gold Member

    Can you account for the discrepancy with an assumption of partial hydrolysis?
  4. Jan 7, 2016 #3
    I dont know what that means, we havent learned it in class.
  5. Jan 8, 2016 #4


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    Staff: Mentor

    Sounds cryptic to me.

    But to be honest - your post starts with CaOH instead of Ca(OH)2 and contains statements like

    so I am not convinced the problem is correctly represented.
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