entropy - K=7.98 Q=c water*m water(t final-t initial...

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Entropy April 9, 2008 Section 2731/2712 Chemistry 002 Ruili Nick Hookham Purpose -
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To determine the entropy change in a reaction of urea and water. Procedure - Weigh 2-4g of urea to 3 decimal places and slowly add water while stirring. Measure the exact volume when urea is completely dissolved. Repeat at least one more time. Then use a calorimeter to measure enthalpy change, using a Styrofoam cup and a thermometer measure out 20-200mL of water and measure the temp every 15 sec for 90 sec. Then put in enough urea to make a 1M solution and measure the temp until it has reached a max or min. Data - Mass urea 1- 2.095 g mL water 1- 4.2mL Mass urea 2- 2.206g mL water 2-4.6mL average k=8.145 part 2 2.999g urea 50mL water Just water water and urea Time Temp Time Temp
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15 26.2 90 26 30 26.5 105 25 45 26.7 120 24.2 60 26.7 135 23.7 75 26.8 150 23.8 90 26.8 Calculations - K=mass urea/MW urea/L water K=2.206/60.06/.0046
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Unformatted text preview: K=7.98 Q=c water *m water *(t final-t initial ) Q=4.184*50*(23.7-26.8) Q=-750.2 J Discussion-It was found that the q was -750.2J and that the k of urea is about 8.145. The reaction was endothermic and the reaction is not spontaneous. Entropy also was lost in this reaction. And if the experiment were done at a greater temp, ΔH would be different because it would not drop as much if at all. The error was abundant in the first part of this lab because it was extremely easy to add too much water because the dissolving took too long to be sure how much water to add. Also the temperature change was relatively low in the second part and thus caused for another chance for human error. Conclusion-Thus in this experiment it was shown how to find the entropy by measuring the k value and the enthalpy....
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This lab report was uploaded on 04/17/2008 for the course CHEM 2 taught by Professor Ryan during the Spring '08 term at Marquette.

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entropy - K=7.98 Q=c water*m water(t final-t initial...

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