Chemistry 202/212
Worksheet 8
Winter 2005
January 13
Oregon State University
1. The vapor pressure of I2(s) at 30C is 0.466 mrn Hg.
(a) How many milligrams of iodine will sublime into an evacuated 1.00-L flask?
6.26 mg
(b) If 2.0 mg of I2 is used, what will the final pressure be?
0.149 mm Hg
(c) If 10.0 mg of I2 is used, what will the final pressure be?
0.466 mm Hg
2. Mt. McKinley in Alaska has an altitude of 20,320 ft. Water (Hvap = 40.7 kJ/mol) boils
at 77ºC atop Mt. McKinley. What is the normal atmospheric pressure at the summit?
0.422 atm
3. At a resort in Sante Fe, New Mexico, the barometric pressure is 625 mm Hg. Water
boils in an open pot at 94.5ºC. A pressure cooker is set for 1.75 atm. (For water,
Hvap = 40.7 kJ/mol)
(a) At what temperature will water boil in that pressure cooker? 116.6ºC
(b) What is the difference between the boiling point in the open pot and in the
pressure cooker?
22.1ºC
4. Referring to the figure, state what
phase(s) is (are) present at
(a) -30ºC, 5 mrn Hg
solid
(b) 70ºC, 20 mrn Hg
vapor
(c) 0.5 atm, l00ºC
vapor
(d) 25ºC, 1 atm
liquid
(e) 1 atm, l00ºC
liquid and vapor
(f) 0.8 atm, 50ºC
liquid
5. Arrange the following in order of decreasing boiling point.
(a) I2 (b) F2 (c) Cl2 (d) Br2
I2 > Br2 > Cl2 > F2
6. Which of the following would you expect to show dispersion forces? Dipole forces?
(a) GeBr4
(b) C2H2
(c) HF (g)
(d) TeCl2
disperson
dispersion
dipole
dipole
7. Which of the following would show hydrogen bonding?
(a) CH30H
(b) N(CH3)3
(c) CH3NH2
yes
no
yes
(e) CH3F
no
(f) HO-OH
yes
(g) NH3
yes
(d) HF
yes
(h) H3C-0-CH3
no
8. In which of the following processes is it necessary to break covalent bonds as opposed
to simply overcoming intermolecular forces?
(a) melting mothballs made of naphthalene
intermolecular
(b) dissolving HBr gas in water to form hydrobromic acid
covalent
(c) vaporizing ethyl alcohol, C2H5OH
intermolecular
(d) changing ozone, 03, to oxygen gas, 02
covalent
(e) subliming Dry Ice
intermolecular
(f) vaporizing chloroform (CHCl3)
intermolecular
(g) decomposing water into H2 and 02
covalent
(h) changing chlorine molecules into chlorine atoms
covalent
9. For each of the following pairs, choose the member with the lower boiling point.
Explain your reason in each case.
(a) NaCl or PCl3
NaCl must overcome ionic bonding to dissociate
(b) NH3 or AsH3
NH3 exhibits hydrogen bonding
(c) C3H70H or C2H5OCH3
C3H70H exhibits hydrogen bonding
(d) HI (g) or HCI (g)
HI is more massive and has greater dispersion
10. Classify each of the following solids as metallic, network covalent, ionic, or
molecular.
(a) It is insoluble in water, melts above 500°C, and does not conduct electricity either
as a solid or molten.
network covalent
(b) It dissolves in water but does not conduct electricity as an aqueous solution, as a
solid, or when molten.
molecular
(c) It dissolves in water, melts above 100°C, and conducts
electricity when present in an aqueous solution.
ionic
11. Give the formula of a solid compound containing carbon that is
(a) molecular
(b) ionic
(c) network covalent (d) metallic
CO2
Na2CO3
diamond
none
12. The equation for the reaction between iodide and bromate ions in acidic solution is
6 I- (aq) + BrO3- (aq) + 6 H+ → 3 I2 (aq) +Br- (aq) +3 H2O
The rate of the reaction is followed by measuring the appearance of I2. The following
data are obtained:
[I-]
[BrO3-]
[H+]
Initial Rate (mol/L·s)
0.0020
0.0080
0.0020
8.89 · 10-5
0.0040
0.0080
0.0020
1.78 · 10-4
0.0020
0.0160
0.0020
1.78 · 10-4
0.0020
0.0080
0.0040
3.56 · 10-4
0.0015
0.0040
0.0030
7.51 · 10-5
(a) What is the order of the reaction with respect to each reactant?
[I-]
first order
[BrO3 ]
first order
[H+]
second order
(b) Write the rate expression for the reaction.
reaction rate = k[I-][BrO3-][H+]2
(c) Calculate k.
1.39·106 L3·mol-3·s-1
(d) What is the hydrogen ion concentration when the rate is 5.00·10-4 mol/L·s and
[I-] = 0.5 [BrO3-] = 0.0075 M?
[H+] = 0.00031 M