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Unit 3: Electrochemistry, Nuclear, Organic
Name___________________
Chem 1B Fall 2015 Chapters 18, 19, 20, 24
Electrochemistry Problems
Information Table: Standard Reduction Potentials in Aqueous solution at 25°C
REACTION
E°red (Volts)
F2 (g)
+ 2e-
Cl2 (g) + 2 eO2 (g) + 4H+ + 4e-
Æ 2F- (aq)
2.87
Æ 2 Cl- (aq)
1.36
Æ 2H2O (l)
1.23
NO3- (aq) + 4H+ (aq) + 3e- ÆNO(g) + 2H2O(aq)
Ag+ (aq) + eÆ Ag (s)
0.96
Fe+3(aq) + e- Æ Fe+2 (aq)
Cu+2 (aq) + 2eÆ Cu (s)
2H+ (aq) + 2eÆ H2 (g)
0.771
Fe+3(aq) + 3 eSn+2(aq) + 2 eNi+2 (aq) + 2 e-
Æ Fe (s)
-0.04
Æ Sn (s)
-0.14
Æ Ni (s)
-0.23
Cd+2 (aq) + 2 eÆ Cd (s)
Æ Fe (s)
Fe+2(aq) + 2 eNiO2(s) + 2H2O(l) + 2e ÆNi(OH)2(s) 2OH-(aq)
Zn+2 (aq) + 2eÆ Zn (s)
1.
0.800
0.337
0.000
-0.40
-0.41
-0.49
-0.763
-0.82
Cd(OH)2 (s) + 2e2H2O (l) + 2e-
ÆCd (s) + 2 OH-(aq)
Æ H2 (g) + 2OH-(aq)
-0.828
Al+3 (aq) + 3eNa+ (aq) + e-
Æ Al (s)
-1.67
Æ Na (s)
-2.714
Consider a galvanic cell in which one half cell contains a silver electrode and 1.0 M
AgNO3 solution and the other half cell has a zinc electrode and 1.0 M Zn(NO3)2
solution.
Choose the left side to be the anode and the right side to be the cathode. Draw a long
and short cell diagram
a)
Label the following: anode; cathode; + electrode; -electrode; zinc electrode; silver
electrode; the solutions in each container; the direction electrons flow and the salt
bridge. Short: Zn | Zn+2 || Ag+ | Ag
b)
c)
Write the half-cell reactions that occur below each half-cell and identify whether it
is reduction or oxidation. Also write the overall reaction.
Oxidation: Zn Æ Zn+2 + 2 e-1
Reduction: Ag+1 + 1e-1 Æ Ag
Overall:
Zn + 2 Ag+1 Æ Zn+2 + 2Ag
In the box for the voltmeter indicate the expected initial voltage for this overall
Zn | Zn+2 || Ag+ | Ag
1.563 V
cell.
2
2.
Balance the half reaction C2H5OH ÆCO2 under acidic conditions, and indicate how
many electrons are transferred for each mole of ethanol (C2H5OH) consumed.
3 H2O + C2H5OH Æ 12 H+1 + 12 e-1 + 2 CO2
3.
Calculate the cell voltage for the reaction
Zn | Zn+2(0.50 M) || H+ (0.0010M); H2(2.50 M) | graphite.
Ecell = E˚cell – (RT/nF) lnQ
E˚cell = 0.763 V, Q = 1.25x 106, Ecell = 0.583V
4.
Balance the following redox reactions using the half reaction method. Label the
reduction and oxidation half reactions and the overall reaction.
a)
MnO4-1 (aq) + SO3-2 (aq) Æ MnO2 (s) + SO4-2 (aq) (basic)
-2
-2
H2O (l) + 2 MnO4-1 (aq) + 3 SO3
(aq) Æ 2 MnO2 (s) + 3 SO4 (aq) + 2OH-1 (aq)
NO3-1 (aq)
8H+1 + 3Zn (s) + 2 NO3-1 (aq)
Æ
b)
Zn (s) +
Æ
Zn+2 (aq) + NO (g)
(acidic)
3Zn+2 (aq) + 2NO (g) + 4H2O (l)
(for part b: include the standard cell potentials of each half cell, the net cell potential and
Predict whether you expect this to be spontaneous or nonspontaneous.)
Zn | Zn+2 || NO3-1, NO | Pt
1.723 V spontaneous
Eox = 0.763V, Ered = 0.96V
5.
In a copper-zinc voltaic cell what is the oxidizing agent?
The one reduced, Cu+2 ions
6.
In the electrolysis of NaCl (aq) , H2 gas is produced at the cathode instead of Na (s).
Explain why.
H2O is easier to be reduced to H2 compared with Na+1 to Na.
7.
The E° value for the standard hydrogen electrode (SHE) is 0.00 volts. How is this value
determined?
Only by experiment
a)
b)
Only by theory
by international agreement
c)
d)
a combination of experiment and theory
e)
none of the above
3
8.
In a voltaic cell made of two metal electrodes and their ions in solution, one electrode
gains mass and the other electrode loses mass. Identify each electrode
a)
Mass is gained at the negative electrode and lost at the positive electrode
b)
Mass is gained at the cathode and lost at the anode
c)
Mass is gained at the anode and lost at the cathode
d)
Voltaic cells are not spontaneous and neither reaction will occur without added
current.
e)
None of the above
9.
Predict the result of using iron nails to fasten an aluminum gutter to a house. Explain
your answer with your knowledge of corrosion. Will the nail, gutter or neither oxidize
and corrode?
Review Corrosion notes:
Al is more easily oxidized compared to Fe, therefore the gutter will corrode.
10.
Compare and contrast a fuel cell verses a primary voltaic cell and include an example of
each.
See notes on Batteries. Primary batteries are one time use; fuel cells constantly add
the reactants and remove the products.
11.
Calculate the grams of aluminum that will be deposited by a current of 0.155 amperes
during a period of
3 hour and 20 minutes from a solution of Al(NO3)3 . (atomic mass of Al = 27.0 g/mol).
0.173g Al
12.
The same quantity of electrical charge that deposited 0.583 grams of silver in a AgNO3
solution was passed through a solution of a gold salt and 0.355 grams of gold was
deposited. What is the oxidation state of gold in this salt? (Au = 197.0 g/mol; Ag =
107.9 g/mol)
Au+3
13.
What are the 3 functions of a salt bridge in a voltaic cell ? and What chemicals or
substances may be in a typical salt bridge?
Salt bridge: median through which ions slowly pass, filled with a nonreactive
neutral salt (examples include KNO3, NaCl) and a substance to keep the salt
solution from flowing out, this can be 5% agar solution (gelatin from algae) or as in
our lab, cotton yarn. A semipermeable porous membrane often replaces the need
for agar. The salt bridge serves 3 functions: 1) makes electrical contact completing
the circuit, 2) maintains electrical neutrality, 3) prevents the spontaneous mixing of
the half cells
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14.
Using the table on the first page answer the following questions regarding the reactions
below.
Fe+3 /Fe+2 Zn+2 /Zn (s)Al+3 /Al (s) Ag+ /Ag (s) Cu+2/Cu (s)
a)
Arrange the oxidizing agents in order of increasing strength.
(Just show oxidizing agent ion or element)
Reduction: weak to strong
Al +3, Zn+2, Cu+2, Fe+3, Ag+1
b)
Which is the easiest to be oxidized?
Al (s)
c)
Which one(s) reduce Fe+3 ions to Fe+2?
Al, Zn, Cu
d)
In a voltaic cell what would be the shorthand way to write the spontaneous reaction
of two half-cells under standard conditions, one contains Fe+3/Fe+2 in contact
with a platinum electrode, the other Cu+2/Cu and what is the initial E°cell.
Cu | Cu+2 || Fe+3, Fe+2 | Pt
0.434 V
15.
A cell is constructed in which identical copper electrodes are placed in 2 solutions.
Solution A contains 1.200 M Cu(NO3)2. Solution B contains Cu+2 ions of a lower
concentration. A salt bridge and exterior wire circuit connect the two solutions. The
potential of the cell is observed to be initially 0.042 V.
a)
What is the [Cu+2] in solution B initially? 0.046M
b)
What is the concentration of [Cu+2] in each of the solutions at equilibrium?
0.623 M
16.
Calculate the oxidation potential (Eox) for hydrogen gas in aqueous basic conditions if
the partial pressure due to hydrogen is 0.750 atm and the pH is 10.85. Use the table on
first page and choose the appropriate half reaction.
H2 + 2 OH-1 Æ 2 H2O + 2 e-1 ; Ecell = 0.828V
[OH-1] = 7.08 x 10-4 M, Q = 2.66 x 106
Eox = 0.638V
17.
Calculate the ΔG° in units of kJ and the equilibrium constant K for the reaction as
written.
Pt(s)|H2(g);H+(aq)||Cu+2(aq)|Cu(s)
Ε°cell = 0.337 V
ΔG° = -65.0kJ/mol; K = 2.52 x 1011
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18.
Nuclear Problems
Write the balanced nuclear equation for the following
242
a)
alpha emission of curium-242 ( Cm)
242
96
b)
Mg Æ
Æ
Pu
0
-1β
+
28
13
Al
0
+1β
118
53
+
I
gamma emission from excited radon-222
222m
86 Rn
19.
238
94
positron emission from xenon-118
118
54 Xe
d)
+
beta emission of magnesium-28
28
12
c)
4
2 He
Cm Æ
Æ
0
0γ
+
222
86
Rn
The decay constant, k, for sodium-24, a radionuclide used medically in blood studies, is
24
4.63 x 10-2 hr-1. What is the half life in hours of Na?
t1/2 = 15.0 hr
20.
Charcoal found in the Lasaux cave in France, site of many prehistoric cave paintings, was
observed to decay at a rate of 2.4 disintegrations per minute per gram of carbon. What is
the age of the charcoal if current living organisms decay at the rate of 15.3 disintegrations
14
per minute per gram of carbon? The half-life of C is 5730 yrs.
15300 yrs old
21.
Californium was first synthesized by bombarding an element with an alpha particle. The
products were Californium-245 and a neutron. What was the target element? Write the
nuclear reaction and the abbreviated notation of the nuclear bombardment reaction.
242
96
22.
Cm +
4
2 He
Æ
1
0n
+
245
98
242
96
Cf
Cm (α, n )
245
98
Cf
Simply describe both nuclear fusion and nuclear fission. Which occurs with larger
nuclides and which with smaller.
See the textbook and notes
23.
Predict the type of radioactive decay process that is likely for each of the following
nuclides and write out the reaction. (There may be 2 choices on one)
a)
14
8O
b)
210
84 Po Æ
c)
212
82 PbÆ
Æ
0
14
β
+
+1
7N
0
210
β
+
-1
85 At
0
212
β
+
-1
83 Bi
0
or
14
8O
or
210
4
84 Po Æ 2 He
14
7N
206
+ 82 Pb
+ -1e Æ +
6
24.
25.
Technetium-99, a major by product of nuclear weapons production, has a half-life of
210,000 years. Neutron bombardment converts it to technetium-100, which decays with
a 16 second half-life to ruthenium-100. Write nuclear equations for these reactions.
a)
99
43 Tc
b)
100
43 Tc
1
+ 0n Æ
Æ
0
-1β
100
43 Tc
100
+ 44 Ru
The most abundant isotope of boron is
11
5 B,
which has a natural abundance of 80.2%.
11
The nucleonic mass of 5 B is 11.006562 amu. Masses of a proton = 1.007276 amu and a
neutron = 1.008665 amu. 1 MeV = 1.6022 x 10-13 J; 1 amu = 931.5 MeV
a) Write out the balanced nuclear equation with boron-11 as the reactant and the
products are only protons and neutrons.
11
5B
1
1
Æ 5 1p + 6 0n
11
b) Solve for the mass defect of 5 B in units of amu/boron-11
Δm = 0.081808 amu
11
c) Solve for the nuclear binding energy of the dissociation of 5 B in units of
a)MeV/boron-11, b) J/boron-11, and c) kJ/mol boron-11 broken into protons and
neutrons.
76.20 MeV/B; 1.221 x 10-11 J/B; 7.353 x 109 kJ/B
26.
Write the balanced nuclear equation for the following
25
a)
electron capture of 13Al
25
13Al
b)
+
25
12Mg
65
29Cu
65
30Zn
Æ +
beta emission of
65
29Cu
27.
0
-1e
0
Æ -1β +
Predict the type of radioactive decay process that is likely for each of the following
nuclides and write out the reaction.
a)
214
82 Pb
Æ
b)
232
90
Æ
c)
40m
18 Ar
Th
0
-1β
214
83 Bi
228
4
2 He + 88 Ra
40
0
Æ Æ
+
0γ
+
18Ar
7
28.
Fill in the missing piece and write the abbreviated form of the following nuclear
bombardment reactions.
109
112
1
a)
abbrev.
4 7 Ag + _____ Æ
4 9 In + 0n
109
4 7 Ag
b)
+ 42 He
Æ
112
4 9 In
+ 1
0n
99
+ _____ Æ 0
0γ + 42Mo
1
0
98
99
42Mo + 0 n Æ 0γ + 42Mo
98
42Mo
109
4 7 Ag
(α, n )14192 In
abbrev.
98
42Mo
(n, γ ) 99
42Mo
29.
A sample of moon rock was analyzed by mass spectroscopy. Only 11.47% of the
40
original 40
19K remained the rest had decayed to 18Ar. The initial amount, N0 would be
100%. Half-life of potassium-40, t½ = 1.28 x 109 yrs.
a)
Solve for the rate constant, k.
k = 5.415 x 10-10 yr-1
b)
Approximately, how old is the moon rock?
4.00 x 109 yr, 4 billion years old
30.
There are no stable nuclides with an atomic number greater than
83
31.
pressure
Rate of Radioactive Decay-does not change with
temperature
or chemical environment
.
,
32.
List several applications of nuclear chemistry.
.
Refer to notes and the textbook.
33.
34.
Of the 2 isotopes, iodine-136 and iodine-122, one decays by beta emission and the other
by positron emission. Identify which is which and write out the expected radioactive
decay reactions.
136
53 I
Æ
122
53 I
Æ
0
-1β
0
+1β
+
+
136
54
Xe
122
52
Te
Organic Problems
What functional groups are present in
CH3- C-CH2-CH-CH=CH-CH3
||
(a)
(b)
(c)
(d)
(e)
|
O
OH
ketone, alkene, alcohol
carboxylic ester, alkene, alcohol
aldehyde, alcohol, amine
phenol, carboxylic acid, alkene
amide, ether, thiol
8
35.
What is the geometry of a propane molecule?
a)
Planar with bond angles of 120°.
b)
Three-dimensional with bond angles of 90°.
c)
Three-dimensional with bond angles of 109.5°.
d)
Three-dimensional with bond angles of 120°.
e)
Three-dimensional with bond angles of 180°.
36.
Why is the following name incorrect?
4-ethyl-5-methylcyclohexane
a)
It is not named with the lowest possible numbers.
b)
Cycloalkanes do not contain alkyl groups attached to the ring.
c)
Ethyl and methyl groups are not found adjacent to one another on a ring.
d)
All of the above.
How many hydrogen atoms are there in 1,4-dimethylbenzene?
a) 2 b) 4 c) 6 d) 8 e) 10
37.
38.
When is Markovnikov's rule needed and what does is say?
The “rich” get “richer”, The carbon with more hydrogen will favor taking on an
additional H atom during addition reactions
39.
Define what is meant by the term structural isomer and give an example.
Structural isomers have the same chemical formula, but are arranged and bonded
in a different order as in hexane verses 2-methylpentane
40.
Reactions:
Finish and balance the following reactions,
classify type of reaction as Addition, Substitution, or Combustion,
and if there are two possible results show both and identify which is favored.
H+
+ HNO3
a)
b)
c)
nitrobenzene + H2O
C3H8 +
5 O2
Æ
3CO2 + 4 H2O
Type S
Type C
CH3_CH=CH2 + HBr Æ CH3_CHBr-CH3 (favored product)
Type A
or CH3_CH2-CH2Br
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d)
41.
CH3- CH2-C-H
||
O
+
H2 __Ni__> 1-propanol
Type A
e)
CH2=CH2 + Br2 Æ
f)
CH3_CH=CH2 + H2O __H2SO4__> 2-propanol (favored product)
or 1-propanol Type A
CH2Br -CH2Br
Type A
Ethers, like alkanes are virtually inert. This property makes them valuable as solvents.
What are other important chemical properties of ethers that laboratory workers must
remember?
They are both volatile and flammable, avoid open containers near flames.
42.
Draw the Structures:
If you skip the hydrogens at least put a line to indicate where H belong.
(a) m-dichlorobenzene or 1,3 - dichlorobenzene
(b) 2,2,3,3-tetrabromo-4-methyl-1-octanol
(c) methyl acetate
(d) 3-methyl-2-decanone
(e) 3-ethyl-3,4,6-trimethyl-2-decanone
2-chloro-3-hydroxy-4-methyl octanal
(f)
(g) ortho-dichlorobenze
(h) 3-ethyl-2- hexanone
43.
Name the Structures:
(a) C l O-H CH3
|
|
|
CH C
C
CH- C H 2 -C H 3
|
|
|
|
CH3 C H2 - C H 2 - C H 3
CH3 C l
2,3-dichloro-5-ethyl-4,4-dimethyl- 3-octanol
(b)
CH 3 -O-CH 2 -CH 3
ethyl methyl ether
(c)
CH 3 -C - H
||
O
CH3 - N - CH3
|
CH3
acetaldehyde
(d)
trimethylamine
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(e)
(f)
(g)
44.
H-C-CH2-CH-CH2-CH3
||
|
O
CH3
3-methyl valeraldehyde
3-methyl pentanal
acetamide
CH3-C-NH2
||
O
O
||
C H 3 - C - O -C H 3 methyl acetate
Draw and name all the different possible structural isomers with the formula C6H14
Refer to notes and the textbook.
45.
How many hydrogen atoms are there in 1-chloro-2 methylbenzene
a) 3 b) 4 c) 5 d) 6 e) 7 f) 8 g) 9
46.
Alkenes may have cis and trans isomers.
Draw and identify the cis and trans isomers of 3-heptene
Refer to notes and the textbook.
47.
How can one test for saturation or unsaturation of hydrocarbons, include observations
one would see?
Bromine test: If you add bromine and the brown color disappears it is unsaturated
48.
Circle and identify the functional groups in the structural formula for the low-calorie
sweetener aspartame below.
O
||
H O
C-O-CH3
| ||
|
H-N-C-C-NH-CH-CH2 | |
H CH2 COOH
Amine, amide, carboxylic acid, aromatic, ester
49.
Name the following coordination compound: [Ni(NH3)3(H2O)3]Cl2
a)
nickel(II)trihydrotriamminechloride
b)
nickel(I)triamminetrihydrochloride
c)
dichloronickel(II)triamminetrihydride
d)
nickel(III)chloride
e)
triamminetriaquanickel(II)chloride
50.
51.
Name the following coordination compound: K4[PtBr6]
a)
potassium bromoplatinum(II)
b)
tetrapotassium bromoplatinate(II)
c)
tetrapotassium hexabromoplatinate(II)
d)
potassium hexabromoplatinate(II)
e)
potassium hexabromoplatinate(III)
Determine the formula for the compound, potassium diamminetetracyanocuprate(II).
K2[Cu(NH3)2(CN)4]
K2[Cu(NH3)2(OCN)4]
[KCu(NH3)2(CN)4]
K[Cu(NH3)2(CN)4]
e) K2[(NH3)2(CN)4Cu]
a)
b)
c)
d)
52.
Determine the chemical formula for the compound, diaquadicarbonylzinc dibromoargentate.
a)
b)
c)
d)
e)
[Ag(H2O)2][Zn(CO)2]Br2
[Ag(H2O)2]2 [Zn(CO)2]2Br2
[Zn(H2O)2(CO)2][AgBr2]
[Zn(H2O)2(CO)2]2[AgBr2]
[Zn(H2O)2(CO)2][ AgBr2]2