3. Would You Expect to Find a Significant Degree of Hydrogen Bonding Between Molecules Of

1.  Nitrogen (N2) and carbon monoxide (CO) are isoelectronic. What substance should have the higher melting point?

2.  The phosphine (PH3) and hydrogen sulfide (H2S) molecules each contain 18 electrons. Their dipole moments are 0.58 and 0.97 D, respectively. Which substance should have the higher boiling point ?

3.  Would you expect to find a significant degree of hydrogen bonding between molecules of:

a)  NH3 b) CH3OH c) HBr d) PH3 e) CH3F f) CH3NH2

4. Which molecule should have the higher melting point?

a) O2 or Cl2

b) propane, CH3CH2CH3 or butane, CH3CH2CH2CH3

c) CH4 or SiH4

4. In each of the following groups of substances, pick the one that has the given property. Justify each answer.

Largest vapor pressure at 100 K: SiH4 CH4 GeH4 SnH4

Highest boiling point: H2S H2Se H2Te H2O

5. In each of the following groups of substances, pick the one that has the given property. For each species you must describe the appropriate attractive force and estimate its strength. The attractive force may be an intermolecular force or if the species does not have discrete molecules, a force of attraction between entities.

For those molecules where polarity is an important issue in assessing the strength of the force, you must clearly show how you estimate the molecules polarity.

a) Highest boiling point: CO2 Hg SnO2 C4H10

b) Largest vapor pressure at 25°C: SiO2 PH3 NH3 PCl3

c) Lowest boiling point: SbH3 NH3 AsH3 PH3

d) Smallest vapor pressure at 25°C: CH4 CH3CH3 CH3OH CH3CH2OH

e) Highest boiling point: KCl H2O H2S CH4

6. Predict which substance in each of the following pairs would have the strongest dipole-dipole

intermolecular forces You must show your reasoning. Take the Pauling electronegativity value for Xe as 2.6.

a) CO2 or OCS

b) SO3 or SO2

c) OCl2 or XeCl2

d) SiF4 or SF4