CHEM 10061
Exam #1
Name___________________
Date____________________
Cg1
Cg2
g
°
Equations: V = nRT = MRT, n = m.w. , P
= P , Pa = XaPa , T = m•K•i,
g1
g2
Hv ap  1
P
1
  
q = m•s•T, 2d sin  = n, ln 1 
P2
R  T2 T1 
Constants: R = 0.0821 L-atm/mol-K or 8.314 J/mol-K or 62.36 L-torr/mol-K
Multiple Choice (3 pts. each)
____1.
Which of the following will be miscible with carbon tetrachloride, CCl 4?
a. NH4Br
b. Br2
c. CH3OH
d. H2O
Determine the value of i (van’t Hoff factor) for a dilute solution of LiBr.
____2.
a. 1
b. 2
c. 3
d. 4
____3. The exothermic step in the dissolution of an ionic compound in water is:
a.
b.
c.
d.
separation of the ions in the salt
separation of the water molecules
hydration (solvation) of the ions in the salt
separation of the ions in the salt and separation of the water molecules
____4. During osmosis
a)
b)
c)
d)
____5.
pure solvent diffuses through a membrane but solutes do not.
pure solutes diffuse through a membrane but solvents do not.
pure solvent and a solution both diffuse at the same time through a membrane.
gasses diffuse through a membrane into a solution and build up pressure.
Which of the following is the most volatile?
a. CCl4
b. CBr4
c. CF4
d. CH4
____6. What is the molality of KBr in a solution made by dissolving 2.21 g of KBr in
897 g of water?
a. 2.46 m
b. 0.0167 m
c. 0.0207 m
d. 2.07 x 10–5 m
____7. As the concentration of a solute in a solution increases, the freezing point of
the solution _________ and the boiling point of the solution __________.
a. increases, increases
c. decreases, increases
b. increases, decreases
d. decreases, decreases
____8. What is the molarity of 0.782 N sulfuric acid (H2SO4) solution?
a. 0.782 M
b. 0.391 M
c. 0.261 M
d. 1.56 M
____9. The vapor pressure of pure water at 25°C is 23.8 torr. Determine the vapor
pressure of a solution prepared by dissolving 18.0 g of glucose (a non-volatile,
non-electrolyte, C6H12O6) into 95.0 g of water at 25°C.
a. 24.3 torr
b. 23.4 torr
c. 0.451 torr
d. 0.443 torr
____10. The temperature at which the vapor pressure of a liquid is equal to the
atmospheric pressure is called the:
a) heat of fusion
c) boiling point
b) heat of vaporization
d) melting point
____11. The direct conversion of a solid to a gas is called:
a. fusion
b. vaporization
c. condensation
d. sublimation
____12. What is the concentration of magnesium ion in ppm for a 0.025 (w/w)%
solution of MgCl2?
a. 250 ppm
b. 64 ppm
c. 186 ppm
d. 500 ppm
____13. Decreasing the total pressure above a liquid will cause the boiling point of the
liquid to:
a) increase
c) remain the same
b) decrease
d) depends on the liquid
____14. Which solution will have the lowest freezing point?
a. 0.030 m glucose(aq) ( a non-electrolyte)
c. 0.030 m AlBr3(aq)
b. 0.030 m CaBr2(aq)
d. 0.030 m NaBr(aq)
____15. Identify the following unit cell:
a) monoclinic
c) primitive cubic
b) body-centered cubic
d) face-centered cubic
____16. Molality is defined as:
moles solute
a. moles solvent
moles solute
b. Liters solution
moles solute
c. kg solution
d.
____17. Vapor pressure of a liquid is dependent upon:
a) temperature
c) volume and temperature
b) volume
d) depends on the liquid
moles solute
kg solvent
____18. Which one of the following will exhibit hydrogen bonding properties?
a. CH3F
b. F2
c. CH3NH2
d. H2S
____19. Calculate the mole fraction of urea (MW = 60 g/mol) in a solution prepared by
dissolving 16 g of urea in 39 g of H2O.
a. 0.36
b. 0.27
c. 0.89
d. 0.11
____20. Which of the following would have the lowest vapor pressure at room
temperature?
a. CH3OH
b. CH4
c. NH3
d. Br2
Solve the following problems showing all work. Use complete sentences for
essay questions. Remember to use proper units, significant figures and
rounding.
1. A solution was prepared by dissolving 6.00 g of a non-electrolyte into enough
benzene to make 75.0 mL of solution. The density of the solution was determined
to be 0.886 g/mL. The normal melting point of benzene is 5.50°C and the molal
freezing point depression constant, Kf, for benzene is 5.12°C/m. The freezing point
of the solution was determined to be 3.85°C. Determine the molecular weight of this
substance. (10 pts.)
2. Bromine melts at -7.00°C and boils at 59.0°C. For this element the heat of fusion
(Hfus) is 10.54 kJ/mol and the heat of vaporization (Hvap) is 30.0 kJ/mol. The
specific heat of liquid bromine is 75.7 J/mol°C. Determine how much heat is
required to convert 5.75 g of solid bromine at -7.00°C to liquid bromine at 30.0°C.
(10 pts.) (Hint: Draw a heating curve for this transformation)
3. Draw a phase diagram for water and label all components of the diagram including
triple point, critical point, axes, phase changes. (10 pts.)
?
A: ?
B: ?
???
C: ?
?
???
4. List the following substances in order of increasing boiling point.
answer. (10 pts.)
HF, KBr, F2, Ne, CH3OH
Justify your