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Exam 1 Review
Supplemental Instruction
Iowa State University
Lindsey
CHEM 178
Vela-Becerra
2/10/14
1.) The following figure represents enthalpy changes accompanying an exothermic
solution process. One letter refers to the overall process of dissolving the solute
in the solvent. Other letters refer to different steps in the solution process but
viewed in a step-wise fashion. Use it to answer the following questions.
a.) Which letter represents the enthalpy change between separated solute
and separated solvent particles to form a solution?
A B C D
b.) Which letter represents the enthalpy change for the heat of solution?
A B C D
Increasing
Enthalpy
B
C
A
D
2.) The molal boiling-point elevation constant for carbon tetrachloride is
2.53 °C/m. This means that 1 m of non-volatile solute particles in carbon
tetrachloride will cause the solution to boil 2.53 °C higher than pure carbon
tetrachloride.
True or False
3.) When a gas condenses the value of this term decreases.
a.) Entropy b.) Mass percent c.) Osmotic Pressure d.) Molality e.) Solubility
4.) The type of chemical equilibrium exemplified by the following reaction is:
BaSO4(s) ⇌ BA2+(aq) + SO42-(aq)
a.) Chemical equilibrium b.) Haber c.) Heterogeneous
d.) Homogeneous
e.) Mass action
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5.) Which of the following factors affect equilibrium concentrations:
(1) magnitude of equilibrium constant; (2) catalyst; (3) initial concentrations of
products and reactants; (4) temperature; (5) overall reaction rate?
a.) (1), (2), (3)
b.) (1), (3), (4)
c.) (1), (2), (3), (4)
d.) (1), (3), (4), (5)
e.) All of them
6.) The position of equilibrium for the reaction
ZnO(s) + H2(g) ⇌ Zn(s) + H2O(g)
does not depend upon which of the following: (1) concentration of ZnO(s); (2)
concentration of H2(g); (3) concentration of Zn(s); (4) concentration of H2O(g);
(5) the value of Kc?
a.) (1), (2), (5)
b.) (2), (3), (5)
c.) (1), (3)
d.) (2), (4)
e.) (5)
7.) Which of the following reactions, initially at equilibrium, will form more product
when the total pressure is increased at constant temperature?
1.) 2CO2(g) ⇌ 2CO(g) + O2(g)
2.) N2(g) + 3H2(g) ⇌ 2NH3(g)
3.) SO2(g) ⇌ S(s) + O2(g)
a.) (1)
b.) (2)
c.) (3)
d.) all of them
e.) none of them
8.) Which of the following reactions, initially at equilibrium, will shift to the left
when the temperature is decreased at constant pressure?
1.) 2C2H2(g) + 5O2(g) ⇌ 4CO2(g) + 2H2O(l)
ΔH = -1297 kJ
2.) CO2(g) ⇌ O2(g) + C(s)
ΔH = +393 kJ
3.) 4Fe(s) + 3O2(g) ⇌ 2Fe2O3(s)
ΔH = -1644 kJ
a.) (1)
b.) (2)
c.) (3)
d.) all of them
e.) none of them
9.) Which of the following is not affected when a catalyst influences a gaseous
chemical reaction?
a.) forward and reverse reaction rates
b.) initial reaction rate
c.) value of activation energy
d.) reaction mechanism pathway
e.) value of equilibrium constant
10.) At 240 °C, the value of Kc is 20 for the reaction
PCl3(g) + Cl2(g) ⇌ PCl5(g)
If a 1.0-L container contains 0.25 mol of PCl5 at 240 °C, how many moles of it
dissociate to form PCl3 and Cl2? (You’ll need to use the quadratic formula to
solve this problem.)
a.) 0.0081 mol
b.) 0.090 mol
c.) 0.0013 mol
d.) 0.11 mol
e.) 0.25 mol
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11.) What is Kc for the following reaction if Kp is 0.76 at 900 K?
2SO3(g) ⇌ 2SO2(g) + O2(g)
a.) 1.3
b.) 0.76
c.) 0.56
d.) 0.050
e.) 0.010
12.) Which statement about catalysts and equilibrium is correct?
a.) A catalyst does not appear in a rate equation; thus it does not affect the
equilibrium.
b.) A catalyst finds a new mechanistic pathway that affects concentrations
differently.
c.) A catalyst affects the rates of the forward and reverse reactions equally;
thus, there is no net change in concentrations.
d.) Solid catalysts, which are common in several industrial applications,
would not affect the equilibrium constant since solids do not appear in the
equilibrium-constant expression.
e.) A different and unique catalyst is needed for every equilibrium at
different temperatures.
13.) A substances that donates a proton in a chemical reaction can be described as:
a.) Bronsted-Lowry acid
b.) Bronsted-Lowry base c.) Conjugate base
d.) Arrhenius acid
e.) Arrhenius base
14.) The hydronium ion is a hydrated hydrogen ion and carries a positive charge.
True or False
15.) Which of the following aqueous solutions will have the lowest freezing point?
a.) 0.0100 m NaCl b.) 0.0100 m Li2SO4
c.) 0.035 m CH3CH2OH
d.) 0.0150 m MgCl2 e.) pure water
16.) Which one of the following is associate with a spontaneous process?
a.) Endothermicity b.) Decreased entropy
c.)Increased order
d.) Releasing energy
17.) A solution with a [OH-] = 5.5x10-5 is
a.) Acidic
b.) Basic
c.) Neutral
18.) What is the value of Kc for the following reaction if the equilibrium
concentrations are [A] = 0.60 M [B] = 0.35 M [C] = 0.55 M?
2 A (aq) + B (aq) ⇌ 2 C (aq)
a.) 0.38 b.) 0.42
c.) 2.40
d.) 2.62
19.) What is the strongest type of interaction?
a.) Ion-dipole b.) Hydrogen bonding
d.) Ion-ion
e.) London dispersion
c.) Dipole-dipole
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20.) Initially 0.035 moles of SO2, 0.5 moles of SO2Cl2, and 0.08 moles of Cl2 are
combined in a 5 liter flask. What is the value of Q and which direction will the
reaction proceed to establish equilibrium?
SO2Cl2 (g) ⇄ SO2 (g) + Cl2 (g)
Kc = 0.078
a) Q = 1.12 x 10-3; forward
b) Q = 1.12 x 10-3; backward
c) Q = 5.6 x 10-3; forward
d) Q = 5.6 x 10-3; backward
21.) Identify the nonelectrolyte.
a.). NaCl
b.) K3PO4
c.) CH3OH
d.) HCl
22.) What is the correct Keq expression for the following reaction?
2 NO(g) + 2 H2 (g) ⇆ N2(g) + 2 H2O(g)
a.) Keq =
[N2 ][H2O]
[NO][H2 ]
[NO][H2 ]
[N ][H O]2
2
2
b.)Keq = [N2 ][H2O] c.) 𝐾𝑒𝑞 = ([NO]
2 [𝐻
2
]2 )
[NO]2 [H2 ]2
d.) 𝐾𝑒𝑞 = [N2 ]2 [H2O]
23.) Consider a solution of urea [(NH2)2CO, molar mass = 60.06 g/mol] in water
[H2O, molar mass = 18.02 g/mol] at 25ºC. At 25ºC PºH2O = 23.8 mmHg. Calculate
the vapor pressure of a solution made by dissolving 115 g of urea in 485 g of water.
PA=XAPAo
a.) 23.8 mmHg
b.) 22.2 mmHg
c.) 20.2 mmHg
d.) 21.4 mmHg
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