exp7 - Experiment 7 Thermochemistry Fall 2007 Name TA Emily...

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Experiment 7 – Thermochemistry Fall 2007 Name Emily Winslett Lab Day and Time Tuesday, 1:00 TA Duy Le Section 409 Documentation Kenan Hill (lab partner), Lab Manual, Pre-lab lecture Possible Points Points Received Introduction 10 Purpose of report Goals of the experiment Materials and Methods 10 Reference lab manual Only describe deviations Results and Discussion 60 Inserted titles for tables Inserted graphs into template Inserted captions for each graph Showed complete sample calculations Summarized all data in tables Answered questions completely Error analysis Laboratory Technique 20 TOTAL (100) TA Comments/Suggestions:
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C HEMISTRY 11L R EPORT T EMPLATE EXPT. Thermochemistry 7 Introduction The purpose of this experiment is to introduce the concept of thermochemistry. Also, the purpose of this experiment and lab report is to prove Hess’s Law. This law states that if a reaction is the sum of two or more other reactions, the enthalpy change for the overall reaction must be the sum of the enthalpy changes for the two other reactions. In this experiment, the enthalpy changes of three reactions were calculated, and then the enthalpies of two were added to that of the third. The enthalpy values calculated in the experiment were then compared to literature values. Materials and Methods The procedure for this experiment was taken from the Chemistry 101 Lab Manual. There were no deviations from the given procedure. Results and Discussion In part A of the experiment an initial volume of a liquid was put in a calorimeter, and then an amount of NaOH was later added. Solid NaOH was used in the first and third reaction, and when the mass was determined it as added to a flask. In the first reaction, 50 mL of water was mixed with 2.064 g of NaOH. The NaOH was added to the water in the calorimeter after 185 seconds. In reaction 2, 50 mL of 1 M HCl was put in the calorimeter, and after 182 seconds 50 mL of liquid NaOH was added to the HCl. In the third reaction, 55 mL of 1 M HCl was diluted to 100 mL, and then after 186 seconds 2.039 g of NaOH was added to the HCl. Table 1. Raw Data of Flask Mass, NaOH Mass, and the Time of Mixing for All Three Reactions Reaction 1 Reaction 2 Reaction 3 Calorimeter Constant Volume (mL) 50 100 100 Hot water: 50.00 g Cold water: 50.00 g Initial Mass Flask (g) 84.735 N/A 80.337 N/A Final Mass Flask (g) 86.799 N/A 82.376 N/A Mass NaOH (g) 2.064 N/A 2.039 N/A Time of Mixing (s) 185 182 186 N/A Table 2 contains the values used to determine the calorimeter constant. The masses of the hot and cold water are included in Table 2. These values are 50.00 g for both, because the volume was 50.00 mL and since the density of water is 1, the mass was equal to the volume. The temperatures of the hot, cold,
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This note was uploaded on 05/01/2008 for the course CHEM 101L taught by Professor Austell during the Spring '08 term at UNC.

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exp7 - Experiment 7 Thermochemistry Fall 2007 Name TA Emily...

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