Lab 6: Heat of Reaction and Hess’s Law Essay

Purpose: The purpose of this lab is to verify Hess’s Law of Additivity of Reaction Enthalpies

Chemical Reaction/Physical Reaction:
1.) Na(aq) + OH(aq) -> NaOH(s)
2.) NaOH + HC2H3O2(aq) -> H2O(l) + Na(aq) + C2H3O2
3.) Na(aq) + OH(aq) + HC2H3O2(aq) -> H2O(l) + Na(aq) + C2H3O2

List of Materials:Digital Thermometer, foamed polystyrene cups (3), 250 mL beaker,Weighing boat or small beaker, Graduated cylinders, 100mL(1), 25 mL(2),sodium hydroxide pellets, sodium hydroxide 2.0M, Acetic acid 1.0M and 2.0M.

Safety Considerations: Always have safety goggles covering your eyes, do not inhale the fumes of chemicals used. Also to not eat or drink chemicals used in this lab.

Procedure:Begin by assembling the calorimeter using styrofoam cups. Poke a hole in the lid. Record the initial temperature of the liquid in the calorimeter. Watch the thermometer until maximum temperature is achieved. Weigh out 2.0g of NaOH pellets. Record the temperature of the distilled water in the calorimeter until the temperature is constant then add all of the pellets at once. Gently stir the pellets until the acid is dissolved by shaking the the apparatus. Lift the calorimeter lid and wash out its contents and the thermometer. Repeat this experiment using 50.0 mL of 1.0M acetic acid. Repeat experiment using 25.0 mL of each 2.0M sodium hydroxide and 2.0M acetic acid.

Data Table(s):

Reaction equation
Mass of solid NaOH
Initial Temp.
Final Temp
Delta T
NaOH
2.0351 g
23.6 C
31.8 C
8.2 C
HC2H3O2
1.9966
24.8 C
41.6 C
16.8 C
NaOH + HC2H3O2

25.4 C
32.8 C
7.4 C



Calculations/Results: 2.0g NaOH/ 40.0g NaOH= .05M NaOH
174.8kj + -351.12kj = -176.32
174.8 + -351.12) - (154.66) / 154.66 = 2.14%
Questions/Problems:Pre-Lab
1.) 2Na+(aq) + OH-(aq)+ HC2H3O2(aq) -> H2O(l) + 2NaOH(s)+C2H3O2-(aq)
2.)Na+(aq) + OH-(aq) -> NaOH(s) +NaOH(s) + HC2H3O2(aq) -> H2O(l) + Na+(aq) + C2H3O2-(aq)
2Na+(aq) + OH-(aq)+ HC2H3O2(aq) -> H2O(l) + 2NaOH(s)+C2H3O2-(aq)
3.) The...