Essay on Chm1046 Experiment 2: Intermolecular Forces

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Experiment 2: Intermolecular Forces
Performed: 9/12/2011
Submitted: 9/20/2011
Chemistry 1046L

The purpose of partI in this experiment is to identify a variety of unknown substances’ properties using observations of the temperature changes that occur during evaporation. We know that substances with weaker intermolecular forces, such as London dispersion, will have a faster vaporization rate and thus a higher temperature difference compared to those with stronger molecular bonds such as hydrogen and dipole-dipole forces. By measuring the average kinetic energy (or the temperature) of the liquid left behind after some evaporation takes place, we can determine its type of intermolecular
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Also, to familiarize students with Boyle’s law to determine the pressure neededin order to determine the unknown triplet point as well as calculating percent error to accurately publish our experimental data.
Dry ice was white, cylindrical shaped solid that smoked and sublimed when placed onto paper towel. The solids were crushed into a fine grain and a few small chunks. While in the pipet, the dry ice crystallized on outside bottom and inside some layer of “fog” and smoke was created. During submersion into the cup of water, the dry ice observed began to liquefy (the triple point) and after the first slight release of the pliers on the pipet, there was an explosion.

P1 V1 = P2 V2
Pressure of the room taken off the barometer: 10125 kPa
1015 kPa X 1 atm = 10.02 atm 101. 325 kPa

(10.02 atm)(5 mL) X (P2 )(3 mL)
P = 16.7 atm
% Error = 16.7 – 5.1X 100 = 233% 5.1

Conclusion: Based on the observations, it is concluded that unknown C is water because this substance has the least decrease in temperature which correlates to high intermolecular forces. Out of the five unknowns, water has the strongest intermolecular forces having hydrogen bonding. The substance with the weakest
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