CHEM 1040L Lecture 9: Experiment 9: Enthalpy of Reaction Lab
Experiment 9
Introduction
The objectives of Experiment 9 were to determine the temperature changes for a series of
chemical processes, to determine the enthalpy changes for the chemical processes, to compare
the enthalpy changes with available literature values, and to test the validity of Hess's Law. This
was accomplished by adding various amounts of solid NH4 and NaOH to the solutions and then
measuring the temperature changes with the probe. The concepts that related to lecture
include enthalpy, Hess's Law, work, and specific heat capacity. The concepts that related to lab
include using the MeasureNet to take plots of temperature versus time, using the temperature
probe, measuring weight and volume, using the analytical balances, and using a calorimeter.
Experimental Procedure
The experimental procedure was downloaded and printed off of Chem21labs.com, titled
"Experiment 9: Enthalpy of Reaction-Hess's Law". It came from pages 9-4 through 9-7. The
procedures were followed exactly as they were stated in the handout, with the exception being
that the distilled water came from the tab, not a container in the room at room temperature.
Results
1. Enthalpy Changes- NH4Cl and NaOH Reaction
Mass of NH4Cl 2.677 2.676
Initial Temperature of NaOH 21.66 21.36
Initial Temperature of water 21.32 21.02
First Step:
Initial Temperature 21.32 21.19
Final Temperature 17.51 21.59
Temperature Change -3.81 0.4
Heat Capacity 209.2 418.4
Q -797.052 167.36
Enthalpy change 797.052 -167.36
Second Step:
Initial Temperature 19.585 21.500
Final Temperature 20.19 20.29
Temperature Change 0.605 -1.21
Heat Capacity 418.4 418.4
Q 253.132 -506.264
Enthalpy change -253.132 506.264
2. Enthalpy Changes- NaOH and HCL Reaction
Mass of NaOH 1.998 2.005
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Document Summary
This was accomplished by adding various amounts of solid nh4 and naoh to the solutions and then measuring the temperature changes with the probe. The concepts that related to lecture include enthalpy, hess"s law, work, and specific heat capacity. The concepts that related to lab include using the measurenet to take plots of temperature versus time, using the temperature probe, measuring weight and volume, using the analytical balances, and using a calorimeter. The experimental procedure was downloaded and printed off of chem21labs. com, titled. The procedures were followed exactly as they were stated in the handout, with the exception being that the distilled water came from the tab, not a container in the room at room temperature. Results: enthalpy changes- nh4cl and naoh reaction. 506. 264: enthalpy changes- naoh and hcl reaction. Questions: 14,7; -44. 2, 15. 00; -34, 2. 04, ;23. 07. There were many possible sources of error in this experiment.