Thermochemistry: an Ice Calorimeter Determination of Reaction Enthalpy

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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 -363.67 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| 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/-464.2x100 = 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....
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