CHEM106 HW1

Chemical bonds holding atoms together within molecules have bond energies of 150-500 kJ/mol. Hydrogen bonding intermolecular attractions between molecules are normally in the 10-25 kJ/mol range, while London dispersion forces and dipole-dipole interactions are typically near 5 kJ/mol.

For a temperature of 298 K, calculate the fraction of molecules that have a kinetic energy greater than 200 kJ/mol.

200000
8.314
298
8.7484E-36

For a temperature of 298 K, calculate the fraction of molecules that have a kinetic energy greater than 15 kJ/mol.

15000
8.314
298
0.002347711

For a temperature of 1000K, calculate the fraction of molecules that have a kinetic energy greater than 15 kJ/mol

15000
8.314
1000
0.164608441

For a temperature or 298 K, calculate the fraction of molecules that have a kinetic energy greater than 5 kJ/mol.

5000
8.314
298
0.132907109

Determine the ratio of the fraction of molecules with at least 5 kJ/mol of kinetic energy to the fraction having 15kJ/mol. Explain the significance of your answer.

5 15 Ration
298 0.132907109 0.002347711 56.61135842
1000 0.548046448 0.164608441 3.329394561

Determine the ratio of the fraction of molecules at 1000 K with at least 15 kJ/mol of kinetic energy to the fraction at 298 K having at least 15kJ/mol. Explain the significance of your answer.

5 15
298 0.132907109 0.002347711
1000 0.548046448 0.164608441

4.123529969 70.11443936

Tabulate all your results clearly

Show the intermolecular forces between two butane molecules and between two methane molecules by showing all bonds in each of the pairs of molecules, by showing and by explaining the specific interactions that occur. Comment on the relative magnitudes of the intermolecular forces between pairs of methane and butane molecules and fully explain the underlying reason for this difference. Look up the boiling points of these substances and explain the reason for this difference.

Show the hydrogen bonding intermolecular forces between two acetic acid molecules by showing all bonds in each of the molecules, by showing the important partial charges that occur and by showing and explaining the specific hydrogen bonding interactions that occur between these molecules.

Three prominent COX-2 inhibitors (Vioxx, Celebrex, and Bextra) have structures published on PubChem that can be accessed through the course medlinks page. Draw the structures of each of these three molecules and show, using arrows, the specific atoms that can serve as either hydrogen bond donors or acceptors.