AVHS • AP Chemistry
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Solutions
Pre-AP Practice
6.
1.
For the following
A 1.37 M solution of citric acid (H3C6H5O7) in
i) pure water
water has a density of 1.10 g/cm3. Calculate the
ii) 0.01 m solution of C12H22O11 in water
mass percent, molality and mole fractions of the
iii) 0.01 m solution of NaCl in water
citric acid.
iv) 0.01 m solution of CaCl2 in water
Choose the one with
2.
Hydrobromic acid (molar mass = 80.9 g/mol) is
a) highest freezing point
commercially available in a 34.0 mass percent
b) lowest freezing point
3
solution which has a density of 1.31 g/cm . What is
c) highest boiling point
the molarity of the commercially available
d) lowest boiling point
hydrobromic acid?
e) highest osmotic pressure
a) 2.75 M
d) 9.35 M
b) 4.45 M
e) 10.2 M
7.
A 1.25 M Cu(NO3)2 (molar mass = 187.56 g/mol)
solution has a density of 1.19 g/cm3. What is the
c) 5.50 M
weight percent Cu(NO3)2 of the solution?
3.
You need 2.0 L of 0.15 M HCl. You only have 12 M
a) 1.88%
d) 14.3%
HCl available How many mL of 12 M HCl will you
b) 2.36%
e) 19.9%
need to make your solution?
c) 10.5%
a) 250
d) 400
b) 25
e) 40
c) 0.25
8. How much energy (in KJ) is required to melt 35.0 g of
benzene, C6H6? The heat of fusion of benzene is
2.37 kJ/mol.
4.
Which solvent, water or carbon tetrachloride, would
you choose to dissolve each of the following:
9.
Which of the following would have the lowest
a) KrF2
d) CO2
freezing point?
b) SF2
e) MgF2
a. pure H2O
c) SO2
b. aqueous FeI3 (0.24 m)
c. aqueous sucrose (0.60 m)
5. Calculate the freezing point and boiling point of an
antifreeze solution that is 50.0% by mass of
d. aqueous glucose (0.60 m)
e. aqueous KF (0.50 m)
ethylene glycol (HOCH2CH2OH) in water.
Ethylene glycol is a nonelectrolyte. (for water:
Kf=1.86 °C/m and Kb = 0.51 °C/m)
10. The limiting van’t Hoff factor for CaI2 would be
a) 1
c) 3
b) 2
d) 4
phase change that will happen as you increase the
11. A 1.35 m aqueous solution of compound X had a
pressure?
boiling point of 101.4ºC. Which one of the
a) freezing
d) condensation
following could be compound X? The boiling point
b) melting
e) sublimation
elevation constant for water is 0.52 ºC/m.
C) boiling
f) deposition
a. C6H12O6 d. Na3PO4
b. CaCl2 e. CH3CH2OH
c. KCl
13. Based on the phase diagram from question 12, as
you go from point 4 to point 2 what is the phase
change that happens at point 3?
a) freezing
d) condensation
b) melting
e) sublimation
C) boiling
f) deposition
Questions 14 – 16 (answer all that apply)
(A) CO2
(B) CH4(C) NH3
(D) Cl2
(E) CH2Br2
14. Which of the above have only London Dispersion
forces?
15. Which of the above have hydrogen bonding?
12. Based on the above phase diagram, if the starting
conditions are 173 K and 200 torr, what is the first
16. Which one of the above compounds would you
expect to have the lowest boiling point?
FRQ
Answer the questions below that relate to the five aqueous solutions at 25° C shown above.
(a) Which solution has the highest boiling point? Explain.
(b) Identify a pair of the solutions that would produce a precipitate when mixed together. Write the
formula of the precipitate.
(c) Which solution would be the least effective conductor of electricity? Explain.
Answers:
1. mass percent = 23.9%; molality
= 1.6 m; mole fraction = 0.028
2. C
3. A
4. A) CCl4 B) H2O C) H2O D) CCl4
E) H20
5. fp = -29.9°C, bp = 108.2°C
6. a) pure water b) CaCl2 sol’n c)
CaCl2 sol’n d) pure water
e) CaCl2 sol’n
7. E
8. 1.06 kJ
9. E
10. C
11. C
12. F
13. C
14. A, B, D
15. C
16. B
FRQ
(a) solution 1, Pb(NO3)2. This compound will dissociate into three ions with the highest total particle
molality. The greater the molality, the higher the boiling point. Solutions 2, 3, and 5 will produce
two ions while solution 4 is molecular.
(b) solution 1, Pb(NO3)2, and solution 2, NaCl. PbCl2
(c) solution 4, C2H5OH. Ethyl alcohol is covalently bonded and does not form ions in water. Therefore,
the solution is not a better conductor of electricity than water, which is also covalently bonded.