CHEM 1412 Practice Exam #3 (Chapters 18,19 & 22)
Name:________________ Score: __________
Part I-Please DO NOT circle. Write the correct answer in space provided.
_____1. Which energy conversion below takes place in a galvanic cell?
A) electrical to chemical
C) mechanical to chemical
B) chemical to electrical
D) electrical to mechanical
_____2. What is the coefficient of Fe3+ in the balanced equation ?
Fe2+ + Cr+6  Fe3+ + Cr3+
A) 1
B) 2
C) 3
D) none of these
_____3. How many electrons are transferred in the following reaction?
2ClO3‾ + 12H+ + 10I‾  5I2 + Cl2 + 6H2O
A) 10
B) 12
C) 5
D) 30
_____4. Which of the following is true for the cell shown here?
Zn(s)  Zn2+(aq)  Cr3+(aq)  Cr(s)
A)
B)
C)
D)
the electrons flow from cathode to the anode
the electrons flow from the zinc to the chromium
the electrons flow from the chromium to the zinc
the zinc is reduced
_____5. Which of the following reactions is possible at the anode of a galvanic cell?
A) Zn  Zn2+ +2e‾
C) Zn2+ + Cu  Zn + Cu2+
B) Zn2+ + 2e‾  Zn
D) Zn + Cu2+  Zn2+ + Cu
_____6. The standard reduction potentials for the following half reactions are given as follows;
Cr3+ + 3e‾  Cr(s)
Br2(aq) + 2e‾  2Br-
E0 = -0.73 V
E0 = +1.09 V
what is the E0 for this cell?
A) 1.82 V
B) 0.36 V
C) 4.75 V
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D) 1.79 V
_____7. A voltaic cell has an E0 value of +1.00 V. The reaction :
A) is not spontaneous
C) has a negative G0
B) has K =1
D) has G0 = 0
_____8. In the following nuclear equation, identify the missing particle.
4320
A) 4622 Ti
Ca +
42
He  ____ +
B) 4621 Sc
11
H
C) 4422 Ti
D) 4218 Ar
_____9. Which of the following represents positron?
A) 11 H
B) 0-1 e
C) 0+1 e
D) 42 He
_____10.Which of the following is a product of alpha decay of 23892 U?
A) 23490 Th
B) 23893 Np
C) 23891 Pa
D) 23592 U
_____11. An unstable isotope of rhenium, 191 Re, has a half-life of 9.8 minutes and is a beta
producer. What is the other product of this reaction?
A) 191Os
B)191 W
C)190 W
D) 190 Os
_____12. Which of the following process increases the atomic number by 1?
A) gamma-ray production
D) positron production
B) electron capture C) beta particle production
_____13. Which of the following balanced equation is labeled incorrectly?
A) Beta decay, 23992 U  23993 Np + 0-1 e
B) Alpha Bombardment, 2411 Na + 42 He 
C) Electron capture, 74 Be + 0-1e  73 Li
D) All are correctly labeled
2713
Al +10 n
_____ 14. Which of the following pairs is incorrect?
A) ethane (C2H6 )
B) hexane (C6H14)
C) decane (C10H22)
D) heptane (C7H14)
_____ 15. Which of the following is general formula for alkene with n-carbon atoms?
A) CnHn
B) CnH2n+2
C) CnH2n
2
D) CnH2n-2
_____ 16. Warfarin is used to prevent blood clots from forming or growing larger in your blood and
blood vessels. How many different functional groups are in Warfarin?
A) 3
B) 4
C) 5
D) 6
_____ 17. What is the correct IUPAC name for the following compound;
Cl
CH3
C=C
Cl
H3C
A) cis-2-chloro-3-chloro--2-butene
C) trans-2,3-dichloro-2-butene
B) 2,3-dichloro-1-methyl-propene
D) 1-chloro-2-methyl-propene
_____ 18. Name the following:
CH2 - CH3
CH3 - C - C
C-H
H
A) 1-hexyne
B) 2-ethynylbutane
C) 3-methyl-1-pentyne
_____ 19. Name the following:
CH2 - CH3
CH3 - CH - CH2 - CH2 - CH - CH3
CH3
A) 2,4-diethylpentane
C) 2-ethyl-5-methylheptane
B) 2,5-dimethylheptane
D) 3,6-dimethylheptane
3
D)3-methyl-4-pentyne
_____ 20. Which of the following is correct condensed formula for isopropanol?
CH3
CH3 - CH2 - CH2 OH
CH3 - CH - CH3
CH3 - C - CH2OH
CH2
CHOH
OH
CH3
C)
CH2
CH2
A)
B)
D)
Part II-Essay questions(Please show all your work for complete credit)
21. The following reaction occurs in basic solution:
MnO2 + HO2‾  MnO4 ‾+ H2O
a) write a balanced equation
b) identify the species which is oxidized
c) identify which species is an oxidizing agent
22. Refer to the following half-reactions below;
MnO4‾ + 8H+ + 5e‾  Mn2+ + 4H2O
Cr2O72‾ + 14H+ + 5e‾  2Cr3+ + 7H2O
E0 = 1.51 V
E0 = 1.33 V
a) when current is allowed to flow, which species is oxidized?
b) what is the value of cell potential, E0?
c) what is the G0 for the cell that utilized this reaction?
d) calculate the value of equilibrium constant at 25 0C for this reaction?
23. If a constant current of 5.0 amperes is passed through a cell containing Cr3+ for 1.0 hour,
how many grams of Cr will plate out on to the cathode? ( the atomic mass of Cr is 51.996
and 1 Faraday = 96485 coulombs)
24. The half-life of Sr-90 1s 28.1 years. How long will it take a 10.0 g sample of Sr-90 to
decompose to 0.10 g?
25. A student gave a molecule the following name; 3-methyl-4- isopropylpentane. However, the
professor pointed out that, although the molecule could be correctly drawn from this name,
the name did not follow systematic (IUPAC) rules. What is the correct (IUPAC) name of the
molecule?
4
26. Identify the following reactions as addition (A), substitution (S), or oxidation (O).
H+
____________
a) CH3 - CH2 - CH = CH2 + H2O
CH3 - CH2 - CHOH - CH3
b) 2 CH3 - CHOH - CH3 + 9O2
6 CO2 + 8 H2O
____________
27. Identify the classification of the following compounds;
O
CH3 - CH - CH2 - CHO
CH3 - CH2 - COOH
CH3
_____________________
____________________
CH3CH2OCH2CH3
CH3 - CH2 - C - CH3
___________________
___________________
28. Complete the following reactions; (write the major products)
COOH
a)
+ CH3CH2OH
b) CH3 - CH2 - CH3 + Cl2
c) CH3 - CH2 - C = CH2
H+
light
+ H2
Ni(s)
CH3
d) CH3 - CH2OH + CH3 - CH2 - CH -OH
CH3
e) CH3 - CH2 - CH = CH2 + HBr
H+
ether
Bonus question- ( 10 points) - Please write all your work.
1. How many isomers are there with the formula C3H5Br? Include both structural and
geometrical isomers. Please draw at least five isomers and name each.
5
CHEM 1412 Practice Exam # 3 (KEY)
Part I.(2 points each)
1. B
2. C Fe2+  Fe3+ + e‾ , Cr6+3e‾  Cr3+ ,
3Fe2+  3Fe3+ +3e‾
3. A
10 I‾  5I2 + 10e‾
4. B
Electrons flow from anode to cathode.
Zn  Zn2+ + 2e‾ (oxidation half)-Anode
Cr3+ +3e‾  Cr (reduction half)-Cathode
5. A
Oxidation occurs in anode.( loss of electron)
6. A
E0red (Cr3+) = –0.73 V (smaller)  E0ox =+0.73 V
E0red (Br2) = +1.09 V (larger)
E0cell = (+0.73V) + (+1.09V) = +1.82V
E0 = 1.00 V > zero ( positive) , spontaneous and
7. C
8. B
9. C
10. A
Zn  Zn2+ +2e‾
G0 < 0.0 ( negative)
11. A
14. D ( C7H14 is heptene and C7H16 is heptane)
15. C
16. A
17. C
18. C
12. C
19. B
13. D
20. B
Part II. ( 6 points each)
21. MnO2 + HO2‾  MnO4‾ + H2O ( basic solution)
MnO2  MnO4‾
HO2‾  H2O
+
MnO2 + 2H2O  MnO4‾ + 4H
HO2‾ +3H+  2H2O
2(MnO2 + 2H2O  MnO4‾+4H+ +3e‾)
3(HO2‾ + 3H+ +2e‾  2H2O)
( MnO2 is oxidized, reducing agent )
( HO2 is reduced, oxidizing agent )
Balance equation in basic solution:
2MnO2 + 3HO2‾  2 MnO4- + H2O + OH- ( basic solution)
22. MnO4‾ + 8H+ +5e–  Mn2+ + 4H2O
Cr2O72‾ + 14H+ + 5e‾  2 Cr3+ + 7 H2O
E0 = 1.51 V (larger), reduced best
E0 = 1.33 V (smaller) , oxidized best
E0ox= –1.33 V
E0cell = (+1.55 V) - (1.33 V) = +0.18 V , G0 = -nFE0cell = – (5e‾)(96500)(+0.18) = – 8.70x104 J
lnK = ( nE0/.0257) = ( 5x0.18/.0257)= 35.1; K = exp35.1 =1.60x1015
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23.
M
It
51.599 (5.0)(1.0)(3600sec)
m Cr = ----- x ----- = --------- x ---------------------------= 3.23 g, Cr will plate out in cathode
n
F
3e‾
96485
24. t =3.32(t1/2) log N0/Nt = 3.32(28.1) log (10.0/0.10) 
t =186 yrs
25.
CH3- CH - CH - CH2 -CH3


CH3- CH CH3
2,3,4- trimethylhexane

CH3
26. a) Addition ( hydration) b) Oxidation (combustion)
27.
Aldehyde , Carboxylic acid , Ether, Ketone
28.
COO-CH2CH3
a)
b) CH3 - CHCl - CH3 + HCl
c) CH3 - CH2 - CH- CH3
CH3
d) CH3 - CH2O - CH - CH - CH
2
3
e) CH3 - CH2 - CHBr - CH3
CH3
Bonus question C3H5Br possible isomers;
Br
CH3
H
CH3
C=C
C=C
H
H
cis -1- bromo- 1-propene
Br
H
CH3 - CBr = CH2
trans -1- bromo- 1-propene
CH2
CH2Br - CH = CH2
3-Bromo-1-propene
CHBr
CH2
Bromocyclopropane
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2-Bromo-1-propene