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AP Chemistry – Lab 07 – Hess’s Law


The goal of this lab is to verify Hess’s Law: if the sum of two chemical reactions is a third reaction then the sum of the two reaction enthalpies is the enthalpy of the third.

Procedure Notes [LINK]

  • make sure that the calorimeter is clean and dry before each use
  • do not contaminate the solutions with each other as that will distory the results
  • any acid spill – neutralize with baking soda
  • any base spill – neutralize with vinegar
  • the smell of ammonia is powerful – be very careful and do not directly smell
  • be sure and ask how to be coached on using the GLX to save files
Data Processing
  • be sure and determine the heat capacity of the calorimeter
  • determine the change in enthalpy for each reaction (per mole)
  • determine the change in enthalpy for the unknown reaction (per mole) using your data
  • calculate the percent difference between the theoretical and experimental values
  • be sure and complete pre-lab if you did not already do so
Posting Information
  • make sure the data, calculations, graphs are in the LNB
  • the final data, calcs, graphs, results should be posted to Tumblr in polished, final form


This entry was posted on November 9, 2011 by in Chemistry, CLab, SHP and tagged , , .


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