Version 024 – Exam 4 – Sutclife – (52410)
1
This printout should have 25 questions.
Multiplechoice questions may continue on
the next column or page – Fnd all choices
be±ore answering.
SPECIAL NOTE: DUE TO THE LOG
ARITHMIC NATURE O² SOME O²THE
EQUATIONS YOU MAY ²IND I² YOU
DO NOT USE THE EXACT CONVER
SION TO KELVIN YOUR VALUE MAY
BE SLIGHTLY DI²²ERENT TO THE AN
SWER. IT SHOULD BE VERY CLOSE.
001
10.0 points
Consider the voltaic cell
Pt

H
2
(1 atm)

H
+
(? M)

Cl
−
(1 M)

AgCl(s)

Ag
2 H
+
+ 2
e
−
→
H
2
E
0
= 0.00 V
AgCl + 1
e
−
→
Ag + Cl
−
E
0
= 0.222 V
I± the measured cell potential ±or the cell is
0.430 volts, what is the pH o± the solution?
1.
3.52
correct
2.
4.00
3.
0.253
4.
less than 1.00
5.
3.75
Explanation:
002
10.0 points
Given the standard electrode potentials
²e
3+
(aq) + 1
e
−
→
2+
(aq)
E
0
= +0.771 V
I
2
(s) + 2
e
−
→
2 I
−
(aq)
E
0
= +0.535 V
calculate
K
c
at 25
◦
C ±or the reaction
2 ²e
3+
(aq) + 2 I
−
(aq)
→
2+
(aq) + I
2
(s)
.
1.
1
.
61
×
10
12
2.
9
.
53
×
10
7
correct
3.
1
.
05
×
10
−
8
4.
1
.
02
×
10
−
4
5.
9
.
76
×
10
3
Explanation:
003
10.0 points
NOTE: The question is just asking you about
THESE Group 1B metals. Dont worry about
other ones as you have no data ±or them.
Consider the ±ollowing standard reduction
potentials:
Cu
2+
+ 2
e
−
→
Cu
E
0
= 0
.
337 V
Ag
+
+ 1
e
−
→
Ag
E
0
= 0
.
7994 V
Au
+
+ 1
e
−
→
Au
E
0
= 1
.
68 V
Which o± the ±ollowing statements about
the ease o± reduction o± Group IB metal ions
is true?
1.
Cu
2+
is easier to reduce than Au
+
.
2.
Ag
+
is easier to reduce than Au
+
.
3.
Au is easier to oxidize than Ag.
4.
Nothing can be predicted about the ease
o± reduction ±rom the data given.
5.
Ag
+
is easier to reduce than Cu
2+
.
cor
rect
Explanation:
004
10.0 points
How many mL o± a 0.001 M chloride solution
must be added to a 100 mL solution o± 7
.
2
×
10
−
5
M Ag
+
solution ±or AgCl to precipitate?
K
sp
(AgCl) = 1
.
8
×
10
−
10
(Neglect dilution by
the added Cl
−
solution.)
1.
Need to know the solution pH to solve
this problem
2.
2.6 mL
3.
40.6 mL
4.
0.03 mL
5.
0.25 mL
correct
Explanation:
005
10.0 points
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View Full DocumentVersion 024 – Exam 4 – Sutclife – (52410)
2
NOTE: C
a
and C
b
reFer to the concentrations
oF acid and base used in the titration described
below.
The curve For the titration oF nitrous acid
(NH
2
) with NaOH(aq) base is given below.
0
2
4
6
8
10
12
14
0
20
40
60
80 100 120 140
Volume oF base (mL)
pH
Estimate the p
K
a
oF nitrous acid.
C
a
=
0
.
64,
C
b
= 0
.
4608, and the volume oF NH
2
is
100 mL.
1.
3
.
3
correct
2.
None oF these
3.
8
.
17
4.
72
5.
36
Explanation:
K
a
= 4
.
5
×
10
−
4
C
a
= 0
.
64
C
b
= 0
.
4608
V
NH
2
= 100 mL
0
2
4
6
8
10
12
14
0
20
40
60
80 100 120 140
Volume oF base (mL)
pH
(72,8
.
17)
(36,3
.
3)
The equivalence point oF this titration is
when the curve is at an in±ection point (nearly
vertical);
i.e.
, at a volume oF 72 mL
.
The pH at the equivalence point oF this
titration is 8
.
17 pH
.
The p
K
a
can be Found at onehalF the vol
ume oF the equivalence point;
i.e.
, at 36 mL.
The p
K
a
is 3
.
3 pH From looking at the graph.
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 Spring '07
 Holcombe
 Electrochemistry, pH, Reaction, Redox, ml

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