# Postlab 5 - Thermodynamics - Enthalpy of Rxn using Calorimetry and Hess's Law.docx

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Chapter 13 / Exercise 12
Introductory Chemistry: A Foundation
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10.  Identify which instrumental  uncertainty(ies) will be most important in  determining the accuracy of this experiment.   List the types of measurements (e.g. mass ...)  you made in the experiment. Using the  uncertainty values for each instrument, determine the % uncertainty in the measurement. (For  example, an uncertainty of 0.01 in a measurement of 100 is a 1 x 10 -2  % uncertainty.)  Which  uncertainty(ies) in measurement limit the number of significant figures for the calculated enthalpy  of formation of MgO(s)?
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Chapter 13 / Exercise 12
Introductory Chemistry: A Foundation
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of MgO(s) except for perhaps the liquid thermometer which was used to check the temperature of the hot water in a general range and didn't need very specific data. So there were many factors that limited the number of significant figures for the calculated enthalpy of formation of MgO. Edit Answer [The temperature change limits the sig figs to 2 for the MgO reaction and 3 for the Mg reaction. You need to quantify the uncertainty for each measurement. ] 11.  Does heat loss to the environment limit the accuracy of the experiment?   If so, explain.  If  you were able to correct for this, you should  include how you did that in your answer. 2 2
Edit Answer [Answer Correct] 12.  Does heat loss to the calorimeter limit the  accuracy of the experiment?   If so, explain.  If  you were able to correct for this, you should  include how you did that in your answer.