CHEM 1412- Practice Final Exam.
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Some equations and constants:
T = Km
P = XP°
 = MRT
ln[A]t = –kt + ln[A]o
1 / [A]t = kt + 1 / [A]o
t1/2 = ln(2) / k
t1/2 = 1 / k{A]o
Kp = Kc(RT)n
ln(k1/k2) = (Ea /R) (1/T2 – 1/T1)
R = 0.08206 L atm mole–1 K–1 = 8.314 J mole–1 K–1
F
= 96485 J/V mol = 96485 C/mol of e-

E = E° – (0.0592/n) log Q
G = –n F E°cell
G = –RTlnKeq
lnNt = –kt + lnNo
Amp = C/sec
R = 8.314 J/mol K
c = 2.998 X 108 m/s
mass of proton = 1.007276470 amu
mass of neutron = 1.008664904 amu
A periodic table is also attached to the end of the exam.
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For show work problems, you must show your calculations and units clearly for credit
or partial credit. Good luck!
1.
Which one of the following substances will be the most soluble in water?
a) KBr
b) C10H8
c) CCl4
d) C8H18
2.
A 0.100 m solution of which one of the following solutes will have the highest boiling point?
a) KNO3
b) Ca(NO3)2
c) Al(NO3)3
d) Na2SO4
3.
In the gas phase reaction below, if the rate of formation of NO2 is 8.24 X 10–4 M s–1, what is the rate of
disappearance of O2?
4 NH3 + 7 O2  4 NO2 + 6 H2O
4.
The rate law for the aqueous reaction H2SeO3 + 6 I– + 4 H+ –––> Se + 2 I3 + 3 H2O is
Rate = k[H2SeO3][I–]3[H+]2. By what factor will the rate increase if we double the concentrations of
all three reactants?
a) 8
b) 32
c) 64
d) 128
5.
Given the rate data below for the reaction 2A + 3B  Products, what is the rate law for this reaction?
–
Exp.
[A], M
[B], M
Rate, M sec–1
1
2
3
0.100
0.200
0.100
0.100
0.100
0.200
4.0 X 10–5
1.6 X 10–4
8.0 X 10–5
a) Rate = k[A][B]
b) Rate = k[A]2[B]
c) Rate = k[A]2[B]2
d) Rate = k[A][B]2
6.
When the concentration of a reactant was 0.100 M, the rate of the reaction was 8.42 X 10–6 M s-1.
When the concentration of the reactant was doubled to 0.200 M, the rate increased to 1.59 X 10–5 M s–1.
What is the order of the reaction with respect to this reactant (the value of “x” in the rate law)
7.
The half-life of iodine-131, a radioactive isotope of iodine, is 8.04 days. If an iodine-131 solution is initially
0.100 M, what will the concentration be after 60 days? Radioactive decay is a first order process.
8.
The reaction NO2 + CO  NO + CO2 follows the rate law Rate = k[NO2]2.
In the mechanism below,
a) which step is the rate-limiting step?
__________
b) which substance is an intermediate in the reaction?
__________
Step 1
Step 2
9.
NO2 + NO2 –––> NO3 + NO
NO3 + CO –––> NO2 + CO2
The equilibrium constant Kp for reaction (1) has a value of 0.112. What is the value of the
equilibrium constant for reaction (2) ?
(1)
SO2 (g) + 1/2 O2(g)
(2)
2 SO3 (g)
a) 0.512
10.
Kp = 0.112
2 SO2 (g) + O2 (g)
b) 2.24
Kp = ?
c) 44.2
Kc = 278 for the reaction 2 SO2 (g) + O2 (g)
a) 0.0462
11.
SO3 (g)
b) 0.334
d) 79.7
2 SO3 (g) at 1000 K. What is the value of Kp?
c) 54.7
d) 3.39
The reaction NH4HS (s)
NH3 (g) + H2S (g) has Kc = 1.2 X 10–4 at 22°C. If a solid sample of
NH4HS is placed in a closed container and allowed to decompose until equilibrium is reached, what
will the equilibrium concentrations of NH3 and H2S be?
a) 0.022 M
b) 0.28 M
c) 0.011 M
d) 0.14 M
12.
Consider the following chemical reaction:
H2 (g) + I2 (g)
2 HI (g)
Kc = 49.5 at 440°C
a) If the equilibrium concentrations of H2 and I2 are 0.25 M each, what is the equilibrium
concentration of HI?
b) If we start with H2 and I2 at 0.25 M each, what will the HI concentration be at equilibrium?
c) If we start with H2 at 0.65 M, I2 at 0.65 M, and HI at 5.00 M, what is the value of Qc? Which way with
the reaction go (forward , reverse , or no change) in order to react equilibrium?
13.
At 25°C a reaction has a rate constant of 0.350 s–1. What is the value of the rate constant at 100°C ?
The activation energy for the reaction is 70.0 kJ/mol.
14.
The molar mass of an unknown molecular solute is determined by dissolving 2.50 g of the
compound in 50.0 g of benzene. The freezing point of the solution was 1.50°C lower than that of
pure benzene. The freezing point depression constant, Kf, for benzene is 5.00 °C/m. What is the
molecular weight of the compound?
15.
What is the coefficient of water when the following equation is balanced in acidic aqueous solution?
a) 5
16.
Cr2O7 2– + Br– 
b) 6
Cr 3+ + Br2
c) 7
d) 8
The half reaction occurring at the cathode in the voltaic cell reaction is :
3 MnO4- (aq) + 24 H+ (aq) + 5 Fe (s)  3 Mn2+ (aq) + 5 Fe3+ (aq) + 12 H2O (l)
a) MnO4- (aq) + 8H+ (aq) + 5e–  Mn2+ (aq) + 4 H2O (l)
b) Fe (s)  Fe3 +(aq) + 3 e–
c) Fe (s)  Fe2+ (aq) + 2 e–
d) Fe2+ (aq)  Fe3+ (aq) + e–
17.
Given the following standard reduction potentials:
Pb2+ (aq) + 2e-  Pb(s)
E° = –0.126 V
Cu2+ (aq) + 2e-  Cu(s)
E° = +0.337 V
calculate E°cell for a voltaic cell based on these half-reactions.
a) 0.463 V
b) 0.211 V
c) 1.95 V
d) -0.211 V
18.
The reaction O2 (g) + 4 H+ (aq) + 4 Fe2+ (aq)  4 Fe3+ (aq) + 2 H2O (l) has E° = +0.46 V. What is
the value of the equilibrium constant for this reaction?
a) 1.05 X 109
b) 2.67 X 1018
c) 4.64 X 10-22
d) 1.27 X 1031
19.
How many grams of copper metal can be obtained by passing a current of 1.50 amp through a
solution of Cu2+ (aq) for 45 minutes?
20.
Write the nuclear equation for the beta decay of iodine-131.
21.
By what process does oxygen-15 decay to nitrogen-15?
a) positron emission
b) alpha emission
c) beta emission
22.
The alpha decay of what isotope of what element produces lead-206?
a) polonium-210
b) thallium-204
c) radon-222
d) gamma emission
d) bismuth-208
23.
Which is the ketone functional group?
O
24.
O
║
║
a) –C–H
b) –C–OH
O
O
║
║
c) –C–CH3
d) –C–NH2
Name the following compound:
CH3
|
CH3CHCH2CH2CHCH2CHCH2CH3
|
|
CH3
CH2CH3
a) 5,7-diethyl-2-methyloctane
c) 5-ethyl-2,7-dimethylnonane
b) 4-ethyl-1,1,6-trimethyloctane
d) 5-ethyl-3,8-dimethylnonane
25. Which one of the conjugate bases of the following Brønsted-Lowry
acids is incorrect?
a. ClO- for HClO
b. HS- for H2S
c. H2SO4 for HSO4d. NH3 for NH4+
26. Predict whether aqueous solutions of the following compounds are
acidic, basic, or neutral. Find the incorrect answer.
a. KNO3 (neutral) b. NaC2H3O2 (basic) c. KClO (acidic)
d. NaCN (basic)
27. Which of the following acids consider as a strong acid?
a. HCN
b. HClO4
c. HF
d. HNO2
28. Calculate the pH of a buffer that is 0.20 M in formic acid and 0.15 M
in sodium formate (Ka = 1.8 x 10-4).
a. 2.4 x 10-4
b. 3.63
c. 0.82
29. Which of the following acid dissociation constants represents a
stronger acid?
a. Ka = 1.8x10-5
b. Ka = 7.4x10-4
c. Ka = 1.45x10-6
30. If X is the solubility of a salt in moles per liter, which one of the
following Ksp expressions is incorrect?
a. Ag2S , Ksp = 4X3
c. BaSO4 , Ksp = 4 X2
b. AgCl , Ksp = X2
d. Cu(OH)2 , Ksp = 4X3
d. 8.33
d. Ka = 6.67x1 0-10