Spring 2014 Final Exam

CHEM 1202
Form
Spring 2014 Final Exam
1
FORM 1
CHEMISTRY 1202
MAIN Final Exam – Spring 2014
Time allowed: 2 hours
On SIDE TWO of the answer sheet (Scantron):
1) Print your LAST NAME then FIRST NAME and bubble it in.
2) Print and bubble in your Student id number.
3) Print and bubble in your FORM number in the grade or education box.
On SIDE ONE (Scantron):
4) Print your name and (the name of your CHEM1202 lecturer in parentheses)
(Cook, Hogan, Hopkins, Kolniak)
5) Answers to the test questions should go on side one. There is exactly one best answer for each
question and you should NOT leave a question blank. On a numerical question, choose the response
closest to the correct answer.
Useful constants and formulas:
J
atm L
R = 8.314 /mol K or R = 0.0821
/mol
0.693
[A]t
=
ln
= −k t
t
1/ 2
k
[A]0
k = Ae − Ea / RT ;ln
o
E cell = E cell
"
C
k1 Ea ⎛ 1 1 ⎞
⎜ − ⎟
=
k2
R ⎜⎝ T2 T1 ⎟⎠
0.0592
logQ or
n
ΔG = −RTlnK + RTlnQ
o
E cell = E cell
"
K eq = e
− ΔG O
J
F = 96,485 /mol or /mol V
RT
lnQ
nF
RT
!
Select standard reduction potentials:
Au3+ (aq) + 3e–  Au (s)
Cl2 (g) + 2e–  2Cl– (aq)
°
!!"#
= +1.50 V
Br2 (l) + 2e–  2Br– (aq)
I2 (s) + 2e–  2I– (aq)
°
!!"#
= +1.07 V
Cu+ (aq) + 1e–  Cu (s)
°
!!"#
= +0.520 V
O2 (g) + 2 H2O (l) + 4 e-  4 OH– (aq)
2H+ (aq) + 2 e–  H2 (g)
°
!!"#
= +0.400 V
Zn2+ (aq) + 2e–  Zn (s)
Al3+ (aq) + 3e–  Al (s) °
!!"#
= –0.760 V
Li+ (aq) + 1e–  Li (s) °
!!"#
= –3.05 V
°
!!"#
= +1.36 V
°
!!"#
= +0.536 V
!°!"# = 0.000 V °
!!"#
= –1.66 V
Kw = 1.0 × 10–14
CHEM 1202
Spring 2014 Final Exam
FORM 1
CHEM 1202
1.
Spring 2014 Final Exam
FORM 1
Nitrogen monoxide reacts with chlorine gas as follows:
2 NO(g) + Cl2(g)  2 NOCl(g)
At 700 K, the equilibrium constant, KP, for this reaction is 0.26. Now, consider the following
conditions at 700 K: P(NO) = 0.16 atm, P(Cl2) = 0.21 atm, and P(NOCl) = 0.11 atm. Which of
the following statements is true?
a.
b.
c.
d.
e.
The reaction proceeds forward towards the equilibrium
The reaction proceeds in reverse towards the equilibrium
The reaction is at equilibrium
The rate of making products is faster than the rate of making reactants.
ΔG= 0
2.
Pick the CORRECT statement about equilibrium from the choices below.
a.
b.
c.
d.
e.
At equilibrium the forward rate constant always equals the reverse rate constant.
At equilibrium both the forward and reverse rates are zero.
As a reaction proceeds forward toward equilibrium the forward rate constant drops.
At equilibrium the concentration of product always equals the concentration of reactant.
At equilibrium the forward reaction rate always equals the reverse reaction rate.
3.
A container is loaded with 1.50 atm of NOBr. Initially, there are no products present. Calculate
the partial pressure of NOBr at equilibrim. Kp = 0.0310
a.
b.
c.
d.
e.
0.100 atm
1.27 atm
1.45 atm
1.37 atm
0.0230 atm
4.
Consider the following reaction:
2NOBr (g) → 2NO (g) + Br2 (l)
CO (g) + H2O (g)
CO2 (g) + H2 (g)
Kc = 9
The initial concentrations are [CO] = [H2O] = 1.00 M and [CO2] = 3.00 M, [H2] = 1.00 M. What
is the equilibrium concentration of [CO2]?
a.
3.31 M
b.
2.69 M
c.
3.25 M
d.
2.75 M
e.
3.00 M
CHEM 1202
Spring 2014 Final Exam
FORM 1
5.
The molar solubility of Ag2CrO4(s) is 6.5 × 10–5 M at 25 °C. What is its solubility product, Ksp,
constant at 25 °C?
a.
b.
c.
d.
e.
Ksp = 1.1 × 10–12
Ksp = 4.2 × 10–9
Ksp = 2.7 × 10–13
Ksp = 5.5 × 10–13
Ksp = 1.7 × 10–8
6.
Consider the following equilibrium: 2 SO3(g)
2 SO2(g) + O2(g)
A mixture of the gases involved in this reaction is allowed to come to equilibrium. Some SO3 is
then removed from this equilibrium mixture, decreasing the partial pressure of SO3. What will
the reaction do in response to this change, and how will the value of K (the equilibrium constant)
be affected?
a.
b.
c.
d.
e.
The reaction will proceed toward reactants with a decrease in K.
The reaction will proceed toward reactants with no change in K.
The reaction will proceed toward reactants with an increase in K.
The reaction will proceed toward products with an increase in K.
The reaction will proceed toward products with a decrease in K.
7.
A 1.0 L saturated solution of Fe(OH)2 is prepared. Once equilibrium is established 5 mL of
0.1 M NaOH solution is added. Calculate ΔGrxn at 298 K for the Fe(OH)2 reaction immediately
after the NaOH is added and before any further reaction takes place. Ignore the change in
volume that occurs when the NaOH is added. Ksp = 1.8 x 10 15
−
a.
b.
c.
d.
e.
17.3 kJ
38.3 kJ
34.2 kJ
40.2 kJ
33.3 kJ
8.
What is the [H3O+] with a pH of 5.30?
a.
b.
c.
d.
e.
5.3 x 10-5 M
5.0 x 10-3 M
2.0 x 10-9 M
5.0 x 10-6 M
4.3 x 10-5 M
9.
Consider 5 separate solutions of 0.5 M each of the following ions, which has the highest pH?
pKa of the conjugate acids are provided in parentheses.
a.
b.
c.
d.
e.
HCOO–
CH3COO–
C2H5COO–
F–
ClO–
(pKa = 3.74)
(pKa = 4.74)
(pKa = 4.89)
(pKa = 3.17)
(pKa = 7.52)
CHEM 1202
Spring 2014 Final Exam
FORM 1
10.
What is the pH of 0.38 M propionic acid, a weak acid with Ka = 1.3 x 10-5?
a.
b.
c.
d.
e.
13.62
10.67
2.65
0.38
5.31
11.
Calculate the pH of 0.050 M KCN solution. The Ka for HCN is 4.9 x 10 10
a.
b.
c.
d.
e.
8.69
11.5
11.0
2.2
5.3
12.
A solution of weak acid is made at a concentration of 1.00 x 10 2 M with a pH of 3.20. What is
the % Ionization for this weak acid in solution?
a.
b.
c.
d.
e.
4.1 %
6.3 %
94 %
96 %
42 %
13.
Which of the following salts is basic?
a.
b.
c.
d.
e.
NH4Cl
NaCl
KClO4
CH3NH3Cl
KNO2
14.
Calculate the pH at the equivalence point when 25.0 mL of 0.50 M weak acid (HA) is titrated
with 25.0 mL of 0.50 M NaOH. Ka for the weak acid is 1.74 x 10-5.
a.
b.
c.
d.
e.
7.00
9.24
2.68
11.32
9.08
−
−
CHEM 1202
Spring 2014 Final Exam
FORM 1
15.
Consider a buffer made from 0.05 M HClO and 0.05 M NaClO. A small amount of HCl is added
to the mixture. What will happen?
a.
b.
c.
d.
e.
The buffer will react with the acid using the reaction HClO + Η Ο → ClO + Η Ο
The buffer will react with the acid using the reaction HClO + OH → ClO + Η Ο
The buffer will react with the acid using the reaction ClO + H+ → HClO
The buffer will react with the acid using the reaction HClO + Η Ο → ClO + ΟΗ
The buffer will react with the acid using the reaction HClO + Η → H2ClO
16.
Which of the following could be a Lewis Base?
−
2
+
3
−
−
2
−
−
−
2
+
2+
I.
II.
Ca
H+
III.
IV.
S
Na+
2-
a.
b.
c.
d.
e.
I only
II only
III only
III & IV only
IV only
17.
The reaction below has ΔH°rxn = 200. kJ; ΔS°rxn = 200. J/K
2 N2O(g) + O2(g)  4 NO(g)
At what temperatures is his reaction spontaneous under standard conditions?
a.
b.
c.
d.
e.
at temperatures greater than 1000 K
at temperatures lower than 1000 K but greater then 298 K
at temperatures lower than 298 K
at all temperatures
no such temperature exists
18.
When 122.6 g of KClO3 is dissolved in 400.0 g of water which has an initial temperature of
25.00 °C, the temperature of the resulting solution process stabilizes at 6.07 °C.
KClO3 (s) → K+ (aq) + ClO3 (aq)
! Sol
What is the molar enthalpy of solution of KClO3 in water, ΔHsol, in kJ/mol? Assume the
specific heat of the mixture is 4.18 J/g °C.
−
a.
b.
c.
d.
e.
ΔHsol = +31.68 kJ/mol
ΔHsol = -31.68 kJ/mol
ΔHsol= +41.37 kJ/mol
ΔHsol= -41.37 kJ/mol
ΔHsol= +1.865 kJ/mol
CHEM 1202
Spring 2014 Final Exam
FORM 1
19.
Calculate the enthalpy of reaction for this reaction
CS2( l ) + 3 O2(g) → CO2(g) + 2 SO2(g)
Given:
C(s) + O2(g) → CO2(g)
ΔH° = -393.5 kJ/mol
S(s) + O2(g) → SO2(g)
ΔH° = -296.8 kJ/mol
C(s) + 2 S(s) → CS2(l )
ΔH° = 87.9 kJ/mol
a.
b.
c.
d.
e.
−2230.0 kJ/mol
−1320.0 kJ/mol
−3378.0 kJ/mol
−1075.0 kJ/mol
−488.0 kJ/mol
20.
From the thermodynamic data given below, calculate Δ S° RXN for the following reaction:
MgCl2 (s) + 2 H2O (l) → Mg(OH)2 (s) + 2 HCl (aq)
Mg(OH)2 (s)
HCl (aq)
MgCl2 (s)
H2O (l)
a.
b.
c.
d.
e.
S°( J/mol·K)
63
187
90
70
– 90 J/K-mol
+ 90 J/K-mol
– 207 J/K-mol
+ 207 J/K-mol
+ 261 J/K-mol
21.
Which of the following statements CORRECTLY describes the relationship between the heat
absorbed by a chemical reaction, q, and the entropy change to the surroundings, ΔSsurr?
a.
b.
c.
d.
e.
If q is positive then ΔSsurr is also positive.
If q is positive then ΔSsurr is zero.
If q is negative then ΔSsurr is zero.
The sign of q is always opposite to that of ΔSsurr.
There is no relationship between q and ΔSsurr.
CHEM 1202
22.
Spring 2014 Final Exam
FORM 1
The formation of nickel tetracarbonyl, Ni(CO)4(g), is exothermic.
Ni(s) + 4 CO(g)  Ni(CO)4(g)
At a temperature at which this reaction is spontaneous, which of the diagrams below correctly
represents the above reaction at standard conditions?
23.
Write the formation reaction for the reaction that has oxygen atom as product. What must be
true for this reaction?
a.
b.
c.
d.
e.
ΔH = 0
ΔH > 0
ΔH < 0
w=0
ΔS = 0
24.
Consider the reaction A + B → C + D. The reaction is second order in A and zero order in B.
When the concentration of A is 0.1 M and the concentration of B is 0.200 M the rate of reaction
is 4.50 M/s. What is the rate of reaction when the concentration of A is 0.250 M and the
concentration of B is 0.500 M?
a.
b.
c.
d.
e.
0.2 M/s
8.6 M/s
16.2 M/s
22.1 M/s
28.1 M/s
CHEM 1202
25.
Spring 2014 Final Exam
FORM 1
The decomposition of hydrogen peroxide is catalyzed by iodide ion. The catalyzed reaction is
thought to proceed by a two-step mechanism:
H2O2 (aq) + I (aq) → H2O (l) + IO (aq)
IO (aq) + H2O2 (aq) → H2O(l) + O2 (g) + I (aq)
−
−
−
−
Step 1, slow
Step 2, fast
What is the rate law for the overall reaction:
2 H2O2 (aq) → 2H2O (l) + O2 (g)
a.
b.
c.
d.
e.
Rate = k[H2O2]2
Rate = 2k[H2O2]
Rate = k[H2O2][I ]
Rate = k[IO ][H2O2]
Rate = k[H2O2]1/2
26.
Which of the following statements are true when temperature increases?
I.
the average energy with which particles collide increases
II.
the rate of a reaction increases
III.
the activation energy decreases
I only
II only
III only
II and III only
I and II only
a.
b.
c.
d.
e.
27.
a.
b.
c.
d.
e.
−
−
The kinetics of the reaction, 4 HBr(g) + O2(g) → 2 H2O(g) + 2 Br2(g), was studied at a certain
temperature with the results shown in the table below. What is the rate law for this reaction
under these conditions?
EXPERIMENT
[HBr] (M)
[O2] (M)
1
2
3
4
0.00382
0.00382
0.00764
0.00764
0.00382
0.00764
0.00382
0.00764
Rate = k [HBr]4[O2]
Rate = k [HBr][O2]
Rate = k [HBr]2[O2]
Rate = k [HBr][O2]2
Rate = k [HBr]2[O2]2
INITIAL RATE
(M/s)
0.0984
0.197
0.197
0.393
CHEM 1202
Spring 2014 Final Exam
FORM 1
28.
Consider a substance that follows first order kinetics has a half-life, t1/2, of 88.90 s. How long
will it take for the concentration to be reduced to 25%?
a.
b.
c.
d.
e.
36.93 s
22.23 s
66.68 s
177.8 s
54.78 s
29.
Which plot will be useful in determining the activation energy of a reaction A products?
a.
b.
c.
d.
e.
ln[A] versus 1/temperature
[A] versus temperature
1/[A] versus time
ln k versus time
ln k versus 1/temperature
30.
Choose the CORRECT statement about the figure shown below from the multiple choices.
a.
The arrow labeled 2 depicts the activation energy for the reverse reaction and the
arrow labeled 1 corresponds to the overall energy change, ΔE, for the reaction.
The arrow labeled 3 depicts the activation energy for the forward reaction and the
arrow labeled 1 corresponds to the overall energy change, ΔE, for the reaction.
The arrow labeled 1 depicts the activation energy for the reverse reaction and the
arrow labeled 3 corresponds to the overall energy change, ΔE, for the reaction.
The arrow labeled 1 depicts the activation energy for the forward reaction and the
arrow labeled 2 corresponds to the overall energy change, ΔE, for the reaction.
The arrow labeled 2 depicts the activation energy for the forward reaction and the
arrow labeled 3 corresponds to the overall energy change, ΔE, for the reaction.
b.
c.
d.
e.
31.
What is the oxidizing agent in this reaction?
a.
b.
c.
d.
e.
2 Na (s) + 2 H2O ( l ) → 2 NaOH (aq) + H2 (g)
Na (s)
H2 O ( l )
NaOH (aq)
H2 (g)
This reaction is not a redox reaction
CHEM 1202
Spring 2014 Final Exam
FORM 1
32.
In a voltaic cell constructed from a strip of zinc immersed in a 1 M solution of Zn2+ions
(E°red = –0.76 V), a strip of copper immersed in a 1 M solution of Cu2+ions (E°red = 0.34 V), salt
bridge, and a wire,
.
a.
b.
c.
d.
e.
electrons flow from the anode to the cathode via the salt bridge
Zn2+ ions flow towards the Zn electrode
cations from the salt bridge flow towards the zinc half-cell
Cu2+ ions are reduced to Cu(s)
the mass of the zinc electrode increases
33.
Consider the following unbalanced redox reaction in an acidic solution?
Sb (s) + Cr2O72 (aq) → Sb2O3 (s) + Cr3+ (aq)
−
How many H+ (aq) are present in the balanced reaction, when balanced using the smallest
possible numbers?
a.
b.
c.
d.
e.
1
2
3
4
8
34.
Calculate the standard emf (E°rxn value) for the reaction shown below using the reduction
potential data on the front of your exam.
−
3 Br2(l) + 2 Al(s) → 2 Al3+(aq) + 6 Br (aq)
a.
b.
c.
d.
e.
E°rxn = +6.53 V
E°rxn = -6.53 V
E°rxn = +2.73 V
E°rxn = -2.73 V
E°rxn = +0.59 V
35.
Calculate the equilibrium constant for this redox reaction at 298 K.
2I (aq) + Br2 (l) → I2 (s) + 2Br (aq)
9.2 x 108
1.3 x 109
6.8 x 1010
1.2 x 1012
8.5 x 1017
−
a.
b.
c.
d.
e.
−
CHEM 1202
36.
Spring 2014 Final Exam
FORM 1
Given the following redox reaction at 298 K:
Au+3 (aq) + 3 Li (s) → Au (s) + 3 Li+ (aq)
Calculate ECELL for a cell operating at these concentrations: [Au3+] = 0.05 M and [Li+] = 0.08 M.
a.
b.
c.
d.
e.
4.59 volts
4.51 volts
4.57 volts
4.53 volts
4.55 volts
CHEM 1202
FINAL EXAM ANSWER KEY
Form 1 & 3
Prob
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Spring 2014
Ans Prob Ans
B
22 A or D
E
23
B
B
24
E
A
25
C
A
26
E
B
27
B
A
28
D
D
29
E
E
30
D
C
31
B
C
32
D
B
33
E
E
34
C
E
35
E
C
36
A
C
A
C
D
D
D
Form 2 & 4
Prob Ans Prob
1
A
22
2
D
23
3
D
24
4
C
25
5
D
26
6 A or D 27
7
B
28
8
B
29
9
E
30
10
B
31
11
A
32
12
A
33
13
B
34
14
A
35
15
E
36
16
C
17
E
18
D
19
B
20
E
21
D
Ans
B
D
E
C
E
A
D
E
C
C
B
E
E
C
C

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