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Chem 222 Lab 5 Report Essay

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IMF: Evaporative Cooling and Molecular Modeling
ChemInquiry 5

Experiment Completed on Tuesday, October 21, 2014
Report turned in on Tuesday, November 3, 2014

Author: Katyna Omidfar-Tran
Partner: Jesus Palomo
Data Analysis Questions
1. Molecular Series I, II, and III all have London Dispersion forces, Dipole-Dipole moment forces, and Hydrogen Bonding forces.
2. Molecular Series IV all have London Dispersion forces only
3. In Molecular Series I (Straight-Chain Alcohols): As you go through the group from methanol  ethanol  1-propanol  1-butanol:
A. The IMFs that are changing in Molecular Series I are London Dispersion forces.
B. Claim: As we go from methanol  ethanol  1-propanol  1-butanol the dispersion forces increase. …show more content…

The more molecules that are able to escape into the vapor, the greater the decrease in temperature due to evaporative cooling. Thus, a larger negative ΔT corresponds to a substance in which the IMFs are weak.
A greater number of electrons correspond to a great polarizability of a molecule. Greater polarizability leads to greater dispersion forces. Thus, as molar mass increases, the number of electrons increase, which increases the polarizability of the molecule and hence the strength of the dispersion forces of the substance.
4. In Molecular Series II (Branched-Chain Alcohols): As you go through the group from 1-butanol  sec-butanol  1-ter-butanol:
A. The dipole moments, surface area (shape), steric hindrances, and change in temperature (degree of evaporative cooling) affect IMF strength and are changing from one molecule to the next.
B. Claim: As we go from 1-butanol  sec-butanol  1-ter-butanol the dipole moments and the surface areas decrease. As we go from 1-butanol  sec-butanol  1-ter-butanol the steric hindrance increases. As we go from 1-butanol  sec-butanol  1-ter-butanol the ΔT (degree of evaporative cooling) decreases. As we go from 1-butanol  sec-butanol  1-ter-butanol the strength of the IMFs decrease.
C. Evidence: As can be seen in Table 2 on page 2A of the attached Appendix, the Spartan molecular modeling data shows surface area decreases in the

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