Thermochemistry: an Ice Calorimeter Determination of Reaction Enthalpy

Thermochemistry: An Ice Calorimeter Determination of Reaction Enthalpy Heidi Moen Chemistry 151 Lab Section No. 47905 09/02/2010 Instructor: John Weide Abstract: In this experiment, an ice calorimeter was used to measure the energy transferred from a system to the surroundings in an isothermal heat transfer. By measuring the change in volume by milliliters before, during, and after a reaction of Sulfuric acid and Magnesium ribbon takes place in the calorimeter reaction test tube. Two trial experiments were preformed. The average of both trials was calculated to be -363. 7 kJ/mol, which is compared to the theoretical yield of enthalpy change; -464. 2 kJ/mol. Lab partner was John Grek.

Results: Table 1 Change in volume in calorimeter after adding magnesium ribbon to Sulfuric acid Time (seconds) Milliliters 0| 0. 79| 60| 0. 73| 120| 0. 57| 180| 0. 46| 240| 0. 39| 300| 0. 345| 360| 0. 315| 420| 0. 299| 480| 0. 28| 540| 0. 27| 600| 0. 265| 660| 0. 26| Table 1 Change in volume in calorimeter after adding magnesium ribbon to Sulfuric acid Time (seconds) Milliliters | 0. 87| 60| 0. 84| 120| 0. 829| 180| 0. 82| 300| 0. 72| 360| 0. 635| 420| 0. 51| 540| 0. 43| 630| 0. 37| 690| 0. 33| 750| 0. 315| 840| 0. 28| 930990 | 0. 270. 26| Sample Calculations Calculations are given for the first addition of magnesium ribbon to H2SO4 0. 82 ml – 0. 32 ml x g/0. 0911 ml x 333 J/g x 1/0. 0049 x kJ/1000J = -372. 99 kJ/mol With the same calculations the result of the second addition of magnesium ribbon to H2SO4 are given -354. 34 kJ/mol Figure 1. Graph of change in volume in calorimeter after adding magnesium ribbon to Sulfuric acid

Figure 2. Graph of change in volume in calorimeter after adding magnesium ribbon to Sulfuric acid Discussion After averaging both trials the results are shown to be -363. 67 kJ/mol, which is compared to the theoretical yield of enthalpy change; -464. 2 kJ/mol. The % error is -363. 67/-464. 2×100 = 78. 34% Conclusion With getting an average ? H of -363. 67 kJ/mol with a 78. 34% yield, the results where unsatisfactory. If having to repeat the experiment, more precise measuring and recording would take place for a more accurate result. GENERAL INSTRUCTIONS

The report must be typewritten (or use a word processor) and should not be written in the first person. Each page should have a 1″ border on all four sides of the page. A page number should appear either in the upper right hand corner (or the bottom center) of each page except the first page of the report. The report should contain each of the following: I. Title Page II. Purpose of the Experiment: This should be a brief statement explaining why the experiment was conducted. (Abstract)Be sure to include names of lab partners and unknown numbers. Or you will lose points. III.

Procedure: A very brief outline of the procedure(s) you used along with a list of any special equipment should be given here. IV. Drawing of Equipment (this is rarely used): A labeled drawing of any specialized equipment setups should be presented here. If you do a drawing, it should look GOOD. A digital photograph is an acceptable substitute. Cameras are available in the stockroom. V. Table of Data and Results: Data and results should be presented in a neat tabular form (must be typed). All Tables should be labeled. All the data should have units. VI. Calculations:

A. Any formulas used should be presented here. A complete setup with UNITS should be shown for each type of calculation. You may accomplish this using an ink pen. B. Graphs should be neat and utilize as much as possible of the whole page without compromising the scaling. Graph title should be an accurate description of what is being plotted. X and Y axes should be labeled to explain both the property plotted and its UNITS. SCALING should be in reasonable increments (i. e. 1, 2, 5, 10 etc. ). For experiments that use the slope, the slope should be printed on the graph. VII.

Questions and Answers: Any questions asked in the lab should be answered here in complete sentences. VIII. Discussion & Conclusion: In this section, the experiment and the results obtained are discussed that results in a conclusion of what was learned. The conclusion should directly address the purpose of the experiment. Also any problems encountered in the experimentation are stated along with any suggestions for improvement of the experiment. IX. Sign and Date your report. Or you will lose points. X. Appendices: Turn in your carbon copy of your data & report sheet as an appendix. Or you will lose points.

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