s obtained by measuring the potential of metal/solution vs the to calculate the
ID: 592200 • Letter: S
Question
s obtained by measuring the potential of metal/solution vs the to calculate the potentials of the combinations measured in silver/silver ion (Ag/Ag+) electrode experiments 1-4. Find the percent error. Next, compare the potential calculated for the electrochemical cells in experiments 1-4 to those calculated using standard reduction potentials found either in your text or the CRC Handbook of Chemistry and Physics (available at the Library reference desk). Calculate the percent error between the values obtained by your measurements and those calculated from the reference. Comment in your conclusions on the value of a reference electrode in measuring electrode potentials.Explanation / Answer
Electrode potential data from text:
Experiment 1:
Cu2+ + 2?e? ? Cu(s) E0red = +0.337 V
Zn2+ + 2?e? ? Zn(s) E0red = ?0.7618 V
Theoretical Potential = -0.7618 – 0.337 = -1.0988 V
= 1098.8 mV
Potential calculated = -1012 mV
% error = |Calculated – Theoretical| / Theoretical * 100
= (-1012 + 1098.8)/1098.8 * 100 = 7.9 %
Experiment 2:
Pb2+ + 2?e? ? Pb(s) E0red = ?0.126 V
Cu2+ + 2?e? ? Cu(s) E0red = +0.337 V
Experiment 3:
Fe2+ + 2?e? ? Fe(s) E0red = ?0.44 V
Zn2+ + 2?e? ? Zn(s) E0red = ?0.7618 V
Experiment 4:
Sn2+ + 2?e? ? Sn(s) E0red = ?0.13 V
Cu2+ + 2?e? ? Cu(s) E0red = +0.337 V
Experiment 5:
Cu2+ + 2?e? ? Cu(s) E0red = +0.337 V
AgCl(s) + ?e? ? Ag(s) + Cl? E0red = +0.2223 V
Ered = E0red – 0.05912/2 * log([Cl-])
= 0.2223 – 0.05912/2 * log(0.1)
= 0.252 V
We can create a table for all experiments as below:
S No.
A
E0red of A
B
E0red of B
Potential mV)
Theoretical potential (mV)
% error
1
Cu2+/Cu
0.337
Zn2+/Zn
-0.7618
-1012
-1098.8
-7.9
2
Pb2+/Pb
-0.126
Cu2+/Cu
0.337
519
463
12.1
3
Fe2+/Fe
-0.44
Zn2+/Zn
-0.7618
-486
-321.8
-51.0
4
Sn2+/Sn
-0.13
Cu2+/Cu
0.337
521
467
11.6
5
Cu2+/Cu
0.337
Ag+/Ag
0.252
-359
-85.11
-321.8
6
Pb2+/Pb
-0.126
Ag+/Ag
0.252
152
377.89
59.8
7
Zn2+/Zn
-0.7618
Ag+/Ag
0.252
635
1013.69
37.4
8
Sn2+/Sn
-0.13
Ag+/Ag
0.252
153
381.89
59.9
9
Fe2+/Fe
-0.44
Ag+/Ag
0.252
138
691.89
80.1
S No.
A
E0red of A
B
E0red of B
Potential mV)
Theoretical potential (mV)
% error
1
Cu2+/Cu
0.337
Zn2+/Zn
-0.7618
-1012
-1098.8
-7.9
2
Pb2+/Pb
-0.126
Cu2+/Cu
0.337
519
463
12.1
3
Fe2+/Fe
-0.44
Zn2+/Zn
-0.7618
-486
-321.8
-51.0
4
Sn2+/Sn
-0.13
Cu2+/Cu
0.337
521
467
11.6
5
Cu2+/Cu
0.337
Ag+/Ag
0.252
-359
-85.11
-321.8
6
Pb2+/Pb
-0.126
Ag+/Ag
0.252
152
377.89
59.8
7
Zn2+/Zn
-0.7618
Ag+/Ag
0.252
635
1013.69
37.4
8
Sn2+/Sn
-0.13
Ag+/Ag
0.252
153
381.89
59.9
9
Fe2+/Fe
-0.44
Ag+/Ag
0.252
138
691.89
80.1
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