INTERMOLECULAR FORCES AND COLLIGATIVE PROPERTIES HOMEWORK
1.
What type of forces, intramolecular or intermolecular,
a. prevent ice cubes from adopting the shape of their container?
b. are overcome when ice melts?
c. are overcome when liquid water vaporizes?
d. are overcome when gaseous water is converted to hydrogen gas and oxygen
gas?
2.
Which forces are intramolecular and which are intermolecular?
a. those preventing oil from evaporating at room temperature.
b. those preventing butter from melting in the refrigerator.
c. those allowing silver to tarnish.
d. those preventing O2 in air from forming O atoms.
3.
At 1.1 atm, will water boil at 100OC? Explain.
4.
A liquid has a ∆HOvap of 35.5 kJ/mole and a boiling point of 122OC at 1.00 atm.
What is the vapor pressure at 109OC?
5.
What is the ∆HOvap of a liquid that has a vapor pressure of 641 torr at 85.2OC and
a boiling point of 95.6OC at 1 atm?
6.
Use the following to draw a qualitative phase diagram for H2. Does H2 sublime at
0.05 atm? Explain.
MP at 1 atm
13.96 K
BP at 1 atm
20.39 K
Triple Point
13.95 K and 0.07 atm
Critical Point
33.2 K and 13 atm
Vapor Pressure of a solid at 10 K
0.001 atm
7.
Why are covalent bonds typically much stronger than intermolecular forces?
8.
Even though molecules are neutral, the dipole-dipole force is one of the most
important interparticle forces that exists among them. Explain.
9.
Polar molecules exhibit dipole-dipole forces. Do they also exhibit dispersion
forces? Explain.
10.
How can one nonpolar molecule induce a dipole in another nearby nonpolar
molecule?
11.
What is the strongest interparticle force in the sample of CH3OH, CCl4, and Cl2?
12.
What is the strongest interparticle force in the sample of H3PO4, SO2, and MgCl2?
13.
What is the strongest interparticle force in the sample of CH3Br, CH3CH3, or
NH3?
14.
What is the strongest interparticle force in the sample of Kr, BrF, or H2SO4?
15.
Which member of each pair of compounds form intermolecular H bonds?
a. (CH3)2NH or (CH3)N
b. HOCH2CH2OH or FCH2CH2F
16.
Which forces oppose vaporization in each of these substances?
a. hexane
b. water
c. SiCl4
17.
Which member of each pair has the highest vapor pressure at a given
temperature? Explain.
a. C2H6 or C4H10
b. CH3CH2OH or CH3CH2F
c. NH3 or PH3
18.
Which member of each pair has the lower vapor pressure at a given temperature?
Explain.
a. HOCH2CH2OH or CH3CH2CH2OH
b. CH3COOH or (CH3)2=O
c. HF or HCl
19.
Which substance has the higher boiling point? Explain.
a. LiCl or HCl
b. NH3 or PH3
c. Xe or I2
20.
Which substance has the higher boiling point? Explain.
a. CH3CH2OH or CH3CH2CH3
b. NO or N2
c. H2S or H2Te
21.
Rank the following in order of increasing surface tension at a given temperature
and explain the ranking.
a. CH3CH2CH2OH b. HOCH2CH(OH)CH2OH
c. HOCH2CH2OH
22.
Rank the compounds in #21 in order of increasing viscosity at a given
temperature and explain the ranking.
23.
For what type of substances is water a good solvent? For what type is it a poor
solvent? Explain.
24.
A water molecule can engage in as many as four H bonds. Explain.
25.
Which forces are overcome in the following events?
a. NaCl dissolves in water b. Kr boils c. water boils
d. CO2 sublimes
26.
Consider the phase diagram of substance X:
A. What phase(s) are present at point A? E? F? H? B? C?
H
B. Which point corresponds to the critical point? Which point
corresponds to the triple point?
C. Which curve corresponds to the conditions of solid-gas
equilibrium?
D. Describe what happens at point A upon the increase in
temperature at constant pressure.
E. Describe what happens at point H upon the decrease in
pressure at constant temperature.
27.
Which gives the more concentrated solution, KNO3 in water or KNO3 in carbon
tetrachloride? Explain.
28.
What is the strongest type of intermolecular force between solute and solvent in
each solution?
a. CH3OCH3(g) in H2O(l) b. Ne(g) in H2O(l)
c. N2(g) in C4H10(g)
29.
What is the strongest type of intermolecular force between solute and solvent in
each solution?
a. C6H14(l) in C8H18(l)
b. H2C=O(g) in CH3OH(l) c. Br2(l) in CCl4(l)
30.
Which solution has the lower freezing point?
a. 10.0 g of CH3OH in 100. g of H2O or 20.0 g of CH3CH2OH in 200. g of H2O
b. 10.0 g H2O in 1.00 kg of CH3OH or 10.0 g of CH3CH2OH in 1.00 kg of
CH3OH
31.
Which solution has the higher boiling point?
a. 35.0 g of C3H8O3 in 250. g of ethanol or 35.0 g C2H6O2 in 250. g of ethanol
b. 20. g of C2H6O2 in 0.50 kg of H2O or 20. g of NaCl in 0.50 kg of H2O
32.
Rank the following aqueous solutions
(I) 0.100 m NaNO3 (II) 0.200 m glucose (III) 0.100 m CaCl2
in order of increasing (A) osmotic pressure (B) boiling point (C) freezing point
(D) vapor pressure at 50OC.
33.
Rank the following aqueous solutions
(I) 0.04 m urea [(NH2)2C=O] (II) 0.02 m AgNO3 (III) 0.02 m CuSO4
in order of increasing (A) osmotic pressure (B) boiling point (C) freezing point
(D) vapor pressure at 298 K.
34.
Calculate the vapor pressure of a solution of 44.0 g of glycerol (C3H8O3) in
500.0 g of water at 25OC. The vapor pressure of water at 25OC is 23.76 torr.
35.
What is the freezing point of 0.111 m urea in water? kf = 1.86°C/m
36.
What is the boiling point of 0.200 m lactose in water? Kb = 0.52°C/m
37.
The boiling point of ethanol (C2H5OH) is 78.5OC. What is the boiling point of a
solution if 3.4 g of vanillin (MM = 152.14 g/mol) in 50.0 g ethanol (Kb =
1.22°C/m)
38.
The freezing point of benzene 5.5OC. What is the freezing point of a solution if
5.00 g of naphthalene (C10H8) in 444 g benzene (Kf = 4.90°C/m)
39.
What is the minimum mass of ethylene glycol (C2H6O2) that must be dissolved in
14.5 kg of water to prevent the solution from freezing at -10.0OF?