Grossmont College Chemistry 120 Exam 4 Spring 2017

Name: ___________________________________Date: ________

Instructor: Diana Vance

Exam 4
Part 1: Multiple Choice (2 points each)
Directions: Please circle the best answer for each of the following questions.
1. Examine the barometer shown below. Convert the pressure reading on the barometer to atm and psi.
a. 0.991 atm; 14.6 psi
b. 0.991 atm; 3.90 × 102 psi
c. 5.72 × 103 atm; 14.6 psi
d. 5.72 × 103 atm; 3.90 × 102 psi
e. 75.3 atm; 1.11 × 103 psi

2. Which of the following gases should have the largest density at STP?
a. CH3CH2CH3
b. C4H10
c. HCN
d. Cl2
e. The density cannot be predicted with the given data.

3. In a gas mixture the partial pressure of helium is 225 torr of neon 375 torr,
and of argon 5 torr. What is the total pressure exerted by the mixture.
a. 605 torr
b. 4.22 × 105 torr
c. It cannot be calculated without knowledge of the container volume.
d. It cannot be calculated without atmospheric pressure.
e. It cannot be calculated without both the container volume and atmospheric pressure.

4. Which of the following properties of liquids is least affected by the strength of intermolecular forces?
a. Vapor pressure
b. Boiling point
c. Heat of vaporization
d. Density
e. Viscosity

5. With all other factors being equal, which of the following correctly lists intermolecular forces in order of
increasing strength?
a. dipole forces < induced dipole forces < hydrogen bonds
b. hydrogen bonds < dipole forces < induced dipole forces
c. induced dipole forces < dipole forces < hydrogen bonds
d. dipole forces < hydrogen bonds < induced dipole forces
e. induced dipole forces < hydrogen bonds < dipole forces

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 Grossmont College Chemistry 120 Exam 4 Spring 2017
Name: ___________________________________Date: ________
Instructor: Diana Vance

6. Which of the following correctly applies to the term “solution”?

a. Heterogeneous mixture
b. Variable composition
c. Constant properties
d. Dissolved particles are usually larger than about 10-7 cm
e. Exist only in the liquid and gas state

7. When a saturated solution is in equilibrium with undissolved solute:

a. the solution separated into layers.
b. dissolving and crystallization stop.
c. the quantity of dissolved solute equals the quantity of undissolved solute.
d. the concentration of the solution remains constant.
e. the temperature increases until more solute dissolves.

8. Which of the following is a characteristic property traditionally associated with an Arrhenius acid?
a. Turns litmus paper blue
b. Feels slippery
c. Tastes bitter
d. Sour taste
e. Contain OH- ions

9. Consider the following generalized reaction.

For this reaction, which of the following is correct?

a. A is a proton source.
b. B is a proton remover.
c. A is an electron pair donor.
d. B is an electron pair acceptor.
e. This is a Lewis acid-base reaction.

10. Which type of glassware is labeled “TC”?

a. Beaker
b. Volumetric flask
c. Florence flask
d. Volumetric pipet
e. Buret

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 Grossmont College Chemistry 120 Exam 4 Spring 2017
Name: ___________________________________Date: ________
Instructor: Diana Vance

Part 2: Short Answer

Directions: Answer each of the following questions. Be sure to use complete sentences where appropriate. For
full credit be sure to show all of your work.

1. A plastic glove when attached to a flask gives the

system a flexible volume. See the illustration
below. From a starting point of 257 mL at 22 °C,
to what volume will the system change if the
temperature rises to 137 °C due to the heating by
the laboratory burner (5 points)?

V1 = 257 mL
T1 = 22 °C + 273 = 295 K
V2 = ?
T2 = 137 °C + 273 = 410 K

V1 V2 T 2 V 1 ( 410 K ) ( 257 mL )
= ⟹ V 2= = =357 mL
T 1 T2 T1 ( 295 K )

2. Identify each as metallic, covalent network, ionic, or molecular solid (5 points).

a. CO2 (s) _________molecular solid
b. NaCl (s) _________ionic solid
c. Ag (s) _________metallic solid
d. C (s), diamond _________covalent network solid
e. I2 (s) _________molecular solid

3. Identify three ways in which you can reduce the amount of time required to dissolve a given
amount of solute in a fixed quantity of solvent (3 points).
Finely dividing a solid offers more surface area per unit of mass. Stirring or agitating the
solution prevents the concentration buildup at the solute surface, which minimizes
crystallization rate. All physical processes speed up at higher temperatures because particle
movement is more rapid.

4. How does the solubility vary with pressure? Compare the effect of pressure change on gases,
liquids, and solids (4 points).
The solubility of liquids and gases is generally not affected by pressure. Gases are always
more soluble at high pressures.

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 Grossmont College Chemistry 120 Exam 4 Spring 2017
Name: ___________________________________Date: ________
Instructor: Diana Vance

5. Assume that 1.50 g of a KClO 3/MnO2 mixture (85% KClO3, by weight) was decomposed in
an experiment similar to yours and all final measurements were made at 22 °C on a day when
the atmospheric pressure was 754 torr (15 points).
a. What is the pressure of the O2 if the vapor pressure of water at 22 °C is 19.827 mm Hg?
PO =P ¯¿−P =754torr −19.827torr =734.173 torr ≈ 734torr ∨0.966 atm¿
2 water

b. What is the balanced decomposition reaction if oxygen gas and potassium chloride are
the products?
2 KClO Mn O22 KCl + 3 O
3 (s)
→
(s) 2 (g)

c. How many moles of O2 should have been evolved?

85 g KCl O3 1 mol KCl O3 3 mol O2
1.50 g mixture × × × =0.016 mol O2
100 g mixture 122.548 g KCl O3 2 mol KCl O3
d. What volume of O2 should have been evolved under experimental conditions?
T = 22 °C + 273 = 295 K

V=
nRT
=
(
( 0.016 mol ) 0.08206
L atm
mol K )
(295 K )
×
760torr
=0.39 L
P (734 torr) 1 atm
e. What is the STP volume of this O2?

V=
nRT
=
L atm
mol K (
( 0.016 mol ) 0.08206
(273 K ) )
=0.35 L
P (1 atm)
6. Place the following substances in order of increasing vapor pressure at a given temperature.
Explain your order (8 points).
nitrogen trifluoride ammonia boron trichloride
NF3 NH3 BCl3

London-dispersion London-dispersion London-dispersion

Dipole-dipole dipole-dipole
Hydrogen bonding

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 Grossmont College Chemistry 120 Exam 4 Spring 2017
Name: ___________________________________Date: ________
Instructor: Diana Vance

So, in order of increasing vapor pressure: NH3 < NF3 < BCl3
7. When tin metal is placed in nitric acid a gas is produced. Remember that metals of variable
charge generally become +2 ions in solution in single replacement reactions (12 points).
a. Write the balanced chemical equation.
Sn (s) + 2 HNO3 (aq)  Sn(NO3)2 (aq) + H2 (g)

b. What volume, in milliliters, of 5.00 M nitric acid is required to react with 100.0 g of tin?
1 mol Sn 2 mol HN O3 1 L HN O3 soln 1000 mL
100.0 g Sn × × × × =337 mL
118.710 g Sn 1 mol Sn 5.00 mol HN O3 1L

8. A solution is made by dissolving 12.50 g of Ba(OH) 2, a strong base, in water to produce 2.0
L of solution (14 points).
a. What is the molarity of the solution?
M =12.50 g Ba ¿ ¿
b. What is the molarity of hydroxide ions?
0.036 M Ba ¿
c. What is the pH of the solution?
pH=14− pOH =14−1.14=12.86
d. What is pOH of the solution?
pOH =−log ¿ ¿
e. Is the solution acidic, basic, or neutral? ___basic_____

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 Grossmont College Chemistry 120 Exam 4 Spring 2017
Name: ___________________________________Date: ________
Instructor: Diana Vance

9. A solution is prepared by dissolving 1.00 g of sodium chloride in enough water to make

10.00 mL of solution (8 points).
a. What is the molarity of the solution?
1 mol NaCl 1 1000 mL
1.00 g NaCl × × × =1.71 M NaCl
58.44 g NaCl 10.00 mL 1L

b. A 1.00 mL portion of this solution is then diluted to a final volume of 10.00 mL. What is
the molarity of the final sodium chloride solution?
M1 = 1.71 M NaCl
V1 = 1.00 mL
V2 = 10.00 mL
M2 = ?

( )
V1 1.00 mL
M 1 V 1= M 2 V 2 ⟹ M 2=M 1 =1.71 M =0.171 M
V2 10.00 mL

10. Name and give the formula for each of the following species (6 points).
a. conjugate base of hydroiodic acid iodide ion, I-
b. conjugate acid of the oxide ion hydroxide ion, OH-
c. conjugate acid of water hydronium ion, H3O+

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