1. Using your knowledge of the types of intermolecular forces present in CO2, CH3CN, Ne, and
CH4 gases, assign each gas to its van der Waals a parameter.
ࡸ૛ ࢇ࢚࢓
a(
࢓࢕࢒૛
)
gas
17.58
3.392
2.253
0.2107
2. Match each liquid to its surface tension (in millinewtons per meter, mN*m-1, at 20˚C).
18.43
22.75
27.80
28.85
72.75
3. The vapor pressure of dimethyl ether at -58˚C is 18.1 kPa and its enthalpy of vaporization is
21.51 kJ/mol. What’s the normal boiling point of dimethyl ether?
4. Given the pressure-temperature phase diagram for CO2 below, answer the following questions.
a.
b.
c.
d.
Label these phases on the diagram: solid, liquid, gas, supercritical fluid
Label these points: triple point, critical point
Label any two points where CO2 is in dynamic equilibrium.
Which CO2 phase is denser, solid or liquid?
e. What’s the normal sublimation point of CO2?
f. What’s the vapor pressure of CO2 at -20˚C?
g. What phase is CO2 in at -80˚C and 700 atm?
5. Using the ideal gas equation and then the van der Waals equation, calculate the pressure at 298
K exerted by 1.00 mol H2 (g) when confined in a volume of a) 30.0 L; b) 1.00 L; c) 50.0 mL.
How does the reliability of the ideal gas law depend on pressure?
6. Using the “like-dissolves-like” rule, explain why soap is effective at removing nonpolar grease
stains from clothing while washing with polar water?
7. The volume of blood in the body of a certain deep-sea diver is about 6.00L. Blood cells make up
about 55% of the volume, and the remaining 45% is the aqueous solution called plasma. What is
the maximum volume of nitrogen measured at 1.00atm and 37°C that could dissolve in the
diver’s blood plasma at a depth of 93m, where the pressure is 10.0atm? Assume that the Henry’s
constant for nitrogen at 37°C (body temperature) is 5.8x10-4 mol/L*atm.
8. a) Fill in the blanks in the figure below with the correct enthalpy change: ∆HL (lattice enthalpy),
∆Hhyd (enthalpy of hydration), and ∆Hsol (enthalpy of solution).
b) Is this an exothermic or endothermic process?
Gas of ions
Enthalpy
Solution
Solid
9. a) The molar solubility of silver bromide, AgBr, at 25°C is 0.88µmol/L. What is the value of Ksp
fro silver bromide?
b) The solubility product of lead(II) fluoride, PbF2, is 3.7x10^-8. Estimate the molar solubility
of the salt.
c) Calculate the solubility of mercury(I) chloride (Hg2Cl2, Ksp=2.6x10^-18) in 0.150M NaCl(aq)
and compare that to the solubility of mercury(I) chloride in pure water.
10. Chloride ion is added to a solution containing the following concentration of soluble salts:
0.020mol/L Pb(NO3)2(aq) and 0.0010mol/L AgNO3(aq).
a. Determine the order in which each ion precipitates as the concentration of chloride ions is
increased and give the concentration of Cl- when precipitation begins.
b. Calculate the concentration of the first ion to precipitate that remains in solution when the
second ion precipitates.
11. The following graph represents the effect of molal concentration of a non-volatile solute (with
i=1.84) on the boiling point elevation of an unknown solvent. Using the graph, determine the
identity of the solvent.
ΔTb vs solute molality for Unknown solvent
ΔTb (oC)
3
2.8
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2
molality (mols / kg)
12. Compare the kf (-1.86 K*kg/mol) and kb (0.512 K*kg/mol) for water. Using these numbers,
estimate why freezing point depression is more commonly used to determine the MW of solutes
than boiling point elevation.
13. Suppose that 10.0 g of an organic compound used as a component of mothballs is dissolved in
80.0 g of benzene. The freezing point of the solution is 1.20 oC.
a. What is an approximate molar mass of the organic compound?
b. Elemental analysis of the substance indicated that the empirical formula is C3H2Cl. What
is its molecular formula?
c. What is the molar mass?
14. A 0.020 M solution of C6H12O6 (aq) is separated from a 0.050 M CO(NH2)2(aq) solution by a
semipermeable membrane at 25 oC. For both compounds i=1.
a. Which solution has the higher osmotic pressure?
b. Which solution becomes more dilute with the passage of H2O molecules through the
membrane?
c. To which solution should an external pressure be applied to maintain an equilibrium flow
of H2O molecules across the membrane?
d. What external pressure (in atm) should be applied in part (c)?
15. Which of the following concentrations of NaCl would raise the boiling point of water the most?
The van’t-Hoff factor does change with concentration, but for this problem we will assume it is
constant.
5% by mass
0.1 m
0.1 M
χNaCl = 0.03
16. List the following aqueous solutions in order of decreasing freezing point. Assume complete
dissociation of all ionic compounds.
0.1 m sugar
0.08 m CaCl2
0.1 m MgCl2
0.12 m KBr