Lab+6+Heats+of+Reaction+and+Hess's+Law


 * Name:** Cullen Orengo


 * Title /Date:** Lab 6: Heat of Reaction and Hess’s Law


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

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
 * Chemical Reaction/Physical Reaction:**


 * 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 ||

174.8kj + -351.12kj = -176.32 174.8 + -351.12) - (154.66) / 154.66 = 2.14% 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 reactions will be endothermic because since all of the temperatures will increase this means that heat is being absorbed. 4.) 2.0g NaOH/ 40.0g NaOH= .05M NaOH 1.)Delta H1= 174.8 kj Delta H2= -351.12 kj Delta H3= 154.66 kj 2.) 174.8kj + -351.12kj = -176.32 3.)(174.8 + -351.12) - (154.66) / 154.66 = 2.14% 4.) This assumption is reasonably valid for reactions 2 and 3 because they are both diluted with water but the first reaction contains no water. 5.)This should be true because if you combine the enthalpy values for 1 and 2 you come relatively close to the value of reaction 3 so either way you flip the equations the sums of two reactions should come close the the third. 6.)If you open the calorimeter before everything is fully dissolved. I feel that this would have the greatest effect on temperature because it would be the best opportunity for heat to escape. 7.) Leftover precipitate from previous trials could alter results of future trials and possibly decrease maximum temperature.
 * Calculations/Results:** 2.0g NaOH/ 40.0g NaOH= .05M NaOH
 * Questions/Problems:****Pre-Lab**
 * Analysis**
 * Analysis/Summary:** Through this lab can be learned how to properly use Hess’s Law. Also the usage of calorimetry can be used in future labs or situations. In this lab you use the Calorimeter to determine the change in temperature and enthalpy throughout different endothermic reactions. These results must then be entered into several equations to find data such as change in enthalpy, quantity of heat released and Moles of different substances. Also the relationships between different reactions containing most of the same solutions or compounds can be clearly seen.