Topics for Day 1: Intermolecular Attractive Forces and Their Relationship to Physical Properties
Read: Sections 1 - 3
Do Problems: 1 - 5, 30, 34, 36, 38, 40

1.  Review ionic vs covalent formulas:

(a) Given the formula of a compound determine if it is molecular or ionic.
(b) Given the formula of a molecular compound determine if it is polar or non polar covalent.

a. Given the formula of a compound, determine the major attractive force.  (ionic = ion-ion and ion-dipole) and (molecular and covalent = dipole-dipole, hydrogen bonding, or London dispersion forces.
b. Given a list of compound formulas rank their attractive forces in order of strength.
c. Describe the relationship between size and strength of London dispersion forces.
d. Given a set of compounds predict their relative orders of boiling point, melting point, DHvap, DHfus, or vapor pressure.

a. Sketch the VSEPR theory shape of a given polar molecule.
b. Indicate the polar parts of the molecule with d+ and d-.
c. Draw arrows showing the relative lengths of the dipole moments in a polar molecule.
d. Show with dots the intermolecular attraction between two molecules.

1.  List the four types of intermolecular forces.

2.  Create graphs (general appearance only) for the boiling points of these similar compounds.
(a) NH3, PH3, AsH3, and SbH3   (b)  CH4, SiH4, GeH4, and SnH4
 

|        |        |        |     bp        |       |        |__________________________             NH3     PH3     AsH3     SbH3

|        |        |        |     bp        |        |        |__________________________             CH4     SiH4    GeH4     SnH4

3.  Why is iodine a solid?

4.  Circle the chemical with the highest melting point:

(a)  F2 or Cl2     (b)  F2 or FCl    (c)  Cl2 or FCl

(d)  NaCl or Cl2    (e)  HF or HBr    (f)  CH3CH2CH3 or CH3CH2CH2OH
 

5.  True or False:
T    F Covalent bonds are weaker than London-dispersion forces

T    F Dipole forces are stronger than London-dispersion forces

T    F Only non-polar molecules have London-diispersion forces

T    F CaS and KCl have similar MMs, however CaS should have a much larger mp.

T    F The heat of vaporization increases with MM for the series (BH2)n

6.  Which exhibits hydrogen bonding in the liquid form?
(a)  H2O    (b)  HI    (c)  HBr    (d)  CH3OH

(e)  N(CH3)3   (f)  CH3OCH3  (g)  HCHO  (h)  CH3COOH

Problem Club Answers:

1.  ion-dipole, dipole-dipole, H-bonding and London-dispersion

2. (a) NH3 = -33 ^oC, PH3 = -87 ^oC, AsH3 = -55 ^oC,  SbH3 -17 ^oC
    (b)  CH4 = -164 ^oC, SiH4 = -111 ^oC, GeH4 -89 ^oC, and SnH4 = -52 ^oC

3.  London-dispersion forces

4.  (a)  Cl2  (b)  FCl  (c) FCl  (d)  NaCl  (e)  HF  (f)  CH3CH2CH2OH
5.  F  T  F  T  T
6.  (a)  H2O  (d)  CH3OH  (h)  CH3COOH