IB Chemistry on Redox Design and Nernst Equation

1. Research Questions:
• Effect Diff ZnSO4 / CuSO4 on emf /current in Voltaic Cell
Mg2+ Cu2+
Mg Cu
Cu
Cu2+
Zn
Zn2+
Cu2+
CuAI
AI3+
Zn Cu
Zn2+ Cu2+
0.1 M 0.1 M
-
-
-
-
-
-
-
-
+
+
+
+
+
+
+
+
0.1 M 1 M
Effect diff metal pairs on emf/current for Voltaic cell
Metal
pair
-ve
terminal
+ve
terminal
E cell/V Current/A
Mg/Cu Mg Cu 2.70 ?
AI/Cu AI Cu 2.00 ?
Zn/Cu Zn Cu 1.10 ?
Fe/Cu Fe Cu 0.80 ?
Sn/Cu Sn Cu 0.48 ?
Research Questions:
• Effect Diff metalpairs on emf/current in Voltaic Cell
Procedure/Method
• Cut metal into (1cm x 1cm) for Mg, Al, Zn, Fe, Sn and Cu
•Prepare 1.0M MgSO4,AI2(SO4)3,FeSO4, SnSO4, CuSO4
• Pipette 5ml 1M CuSO4 into (+) side of well
• Insert Cu to CuSO4 and connect to (+) side of voltmeter
•Pipette 5ml 1M MgSO4 into (-) side of well. Insert Mg into solution.
• Measure emf and current of Mg/Cu cell
•Repeat with diff metal pairs
Metal pair Conc
ZnSO4
Conc
CuSO4
E /V Current/
A
Zn/Cu 0.1 0.1 ? ?
Zn/Cu 0.1 1.0 ? ?
Zn/Cu 0.1 10.0 ? ?
Zn/Cu 1.0 0.1 ? ?
Zn/Cu 10.0 0.1 ? ?
Zn/Cu 10.0 1 ? ?
Zn/Cu 10.0 10.0 ? ?
Zn/Cu 1.0 10.0 ? ?
Effect diff ZnSO4/CuSO4 conc on emf/current for Voltaic cell
Procedure/Method
• Cut metal into (1cm x 1cm) for Zn and Cu
•Prepare 0.1M ZnSO4, CuSO4
• Pipette 5ml CuSO4 into (+) side of well
• Insert Cu to CuSO4 and connect to (+) side of voltmeter
• Salt bridge by soaking cotton string in saturated NaCI
• Pipette 5ml 0.1M ZnSO4 into (-) side of well
• Measure emf and current of Zn/Cu cell
•Repeat with diff conc ZnSO4 and CuSO4 shown

2. Zn2+ Cu2+
Zn Cu
Cu
Cu2+
Zn
Zn2+
Cu2+
CuZn
Zn2+
Zn Cu
Zn2+ Cu2+
-
-
-
-
-
-
-
-
+
+
+
+
+
+
+
+
Effect diff ZnSO4 conc on emf/current for Voltaic cell
Metal pair Conc
ZnSO4
Conc
CuSO4
E cell/V Current/
A
Zn/Cu 10.0 1.0 ? ?
Zn/Cu 1.0 1.0 ? ?
Zn/Cu 0.1 1.0 ? ?
Zn/Cu 0.01 1.0 ? ?
Zn/Cu 0.001 1.0 ? ?
Research Questions:
• Effect Diff ZnSO4 conc on emf /current in Voltaic Cell
Procedure/Method
• Cut metal into (1cm x 1cm) for Zn and Cu
• Pipette 5ml 1M CuSO4 into (+) side of well
• Insert Cu to CuSO4 and connect to (+) side of voltmeter
• Salt bridge by soaking cotton string in saturated NaCI
• Pipette 5ml 10M ZnSO4 into (-) side of well
• Measure emf and current of Zn/Cu cell
•Repeat with diff conc ZnSO4 shown
10 M 1 M 1 M 1 M
Effect diff CuSO4 conc 0n emf /current for Voltaic cell
Metal pair Conc
ZnSO4
Conc
CuSO4
E cell/V Current/
A
Zn/Cu 1.0 10.0 ? ?
Zn/Cu 1.0 1.0 ? ?
Zn/Cu 1.0 0.1 ? ?
Zn/Cu 1.0 0.01 ? ?
Zn/Cu 1.0 0.001 ? ?
Research Questions:
• Effect Diff CuSO4 conc on emf /current in Voltaic Cell
Procedure/Method
• Cut metal into (1cm x 1cm) for Zn and Cu
• Pipette 5ml 10M CuSO4 into (+) side of well
• Insert Cu to CuSO4 and connect to (+) side of voltmeter
• Salt bridge by soaking cotton string in saturated NaCI
• Pipette 5ml 1M ZnSO4 into (-) side of well
• Measure emf and current of Zn/Cu cell
•Repeat with diff conc CuSO4 shown
1 M 10 M 1 M 1 M

3. Effect diff surface area/electrode size on emf/current for Voltaic cell
Zn2+ Cu2+
Procedure/Method
• Cut metal into (1cm x 1cm) for Zn and Cu
• Pipette 5ml 1M CuSO4 into (+) side of well
• Insert Cu to CuSO4 and connect to (+) side of voltmeter
• Salt bridge by soaking cotton string in 1% NaCI
• Pipette 5ml 1M ZnSO4 into (-) side of well
• Measure emf and current of Zn/Cu cell
•Repeat with diff NaCI conc (salt bridge) shown.
Effect diff salt bridge conc on emf /current for Voltaic cell
Zn Cu
Cu
Cu2+
Zn
Zn2+
Conc NaCI
(salt bridge)
Conc
ZnSO4
Conc
CuSO4
E /V Current
/A
Zn/Cu (1.0%) 1.0 1.0 ? ?
Zn/Cu (2.0%) 1.0 1.0 ? ?
Zn/Cu (3.0%) 1.0 1.0 ? ?
Zn/Cu (4.0%) 1.0 1.0 ? ?
Zn/Cu (5.0%) 1.0 1.0 ? ?
Research Questions:
• Effect Diff salt bridge conc on emf /current in Voltaic Cell
Procedure/Method
• Cut metal into (1cm x 1cm) for Zn and Cu
• Pipette 5ml 1M CuSO4 into (+) side of well
• Insert Cu to CuSO4 and connect to (+) side of voltmeter
• Salt bridge by soaking cotton string in saturated NaCI
• Pipette 5ml 1M ZnSO4 into (-) side of well
• Measure emf and current of Zn/Cu cell
•Repeat with electrode size/surface area shown
Metal
pair
Zn size Cu size E cell/V Current/A
Zn/Cu 1 x 1 1 x 1 ? ?
Zn/Cu 2 x 2 2 x 2 ? ?
Zn/Cu 4 x 4 4 x 4 ? ?
Zn/Cu 8 x 8 8 x 8 ? ?
Zn/Cu 16 x 16 16 x 16 ? ?
Research Questions:
• Effect Diff surface area on emf /current in Voltaic Cell
Cu2+
CuZn
Zn2+
Zn Cu
Zn2+ Cu2+
1 % 2 %
-
-
-
-
-
-
-
-
+
+ +
+
+
+
+
+

4. Effect diff cation size/diffusion rate (salt bridge) on emf/current for Voltaic cell
Zn2+ Cu2+
Procedure/Method
• Cut metal into (1cm x 1cm) for Zn and Cu
• Pipette 5ml 1M CuSO4 into (+) side of well
• Insert Cu to CuSO4 and connect to (+) side of voltmeter
• Salt bridge by soaking cotton string in 1% NaF
• Pipette 5ml 1M ZnSO4 into (-) side of well
• Measure emf and current of Zn/Cu cell
•Repeat with diff anion size (salt bridge) shown.
Effect diff anion size/diffusion rate (salt bridge) on emf /current for Voltaic cell
Zn Cu
Cu
Cu2+
Zn
Zn2+
Research Questions:
• Effect Diff anion size on emf /current in Voltaic Cell
Procedure/Method
• Cut metal into (1cm x 1cm) for Zn and Cu
• Pipette 5ml 1M CuSO4 into (+) side of well
• Insert Cu to CuSO4 and connect to (+) side of voltmeter
• Salt bridge by soaking cotton string in 1% LiCI
• Pipette 5ml 1M ZnSO4 into (-) side of well
• Measure emf and current of Zn/Cu cell
•Repeat with diff cation size (salt bridge) shown
Research Questions:
• Effect Diff cation size on emf/current in Voltaic Cell
Cu2+
CuZn
Zn2+
Zn Cu
Zn2+ Cu2+
Cation size
(salt bridge)
Conc
ZnSO4
Conc
CuSO4
E cell/V Current/
A
Zn/Cu (LiCI) 1.0 1.0 ? ?
Zn/Cu (NaCI) 1.0 1.0 ? ?
Zn/Cu (KCI) 1.0 1.0 ? ?
LiCI NaCI
Anion size
(salt bridge)
Conc
ZnSO4
Conc
CuSO4
E
cell/V
Current/
A
Zn/Cu (NaF) 1.0 1.0 ? ?
Zn/Cu (NaCI) 1.0 1.0 ? ?
Zn/Cu (NaBr) 1.0 1.0 ? ?
Zn/Cu (NaI) 1.0 1.0 ? ?
Zn/Cu (NaNO3) 1.0 1.0 ? ?
Zn/Cu (NaSO4) 1.0 1.0 ? ?
NaCINaF
-
-
-
-
-
-
+
+
+
+
+
+
-
-
+
+

5. Effect Temp on emf/current for Voltaic cell
Zn2+ Cu2+
Procedure/Method
• Cut metal into (1 x 1) for Cu and Cu
•Prepare 1M CuSO4, CuSO4
• Pipette 5ml 1M CuSO4 into (+) side of well
• Insert Cu to CuSO4 and connect to (+) side of voltmeter
• Salt bridge by soaking cotton string in 1% NaCI
• Pipette 5ml 1M CuSO4 into (-) side of well
• Measure emf and current of Cu/Cu cell
•Repeat with diff CuSO4 conc shown.
Effect diff CuSO4 conc on emf/current for Copper Conc cell
Zn Cu
Cu
Cu2+
Cu
Cu2+
Research Questions:
• Effect Diff CuSO4 conc on emf /current in Conc Cell
Procedure/Method
• Cut metal into (1cm x 1cm) for Zn and Cu
•Prepare 1.0M ZnSO4, CuSO4 at 25C
• Pipette 5ml CuSO4 into (+) side of well
• Insert Cu to CuSO4 and connect to (+) side of voltmeter
•Pipette 5ml ZnSO4 into (-) side of well
• Measure emf and current of Zn/Cu cell at 25C
•Repeat with diff temp shown
Research Questions:
• Effect Temp on emf/current in Voltaic Cell
Cu2+
CuZn
Zn2+
Cu Cu
Cu2+ Cu2+
Temp/C Conc
ZnSO4
Conc
CuSO4
E cell/V Current/
A
Zn/Cu (4oC) 1.0 1.0 ? ?
Zn/Cu (25oC) 1.0 1.0 ? ?
Zn/Cu (40oC) 1.0 1.0 ? ?
Zn/Cu (50oC) 1.0 1.0 ? ?
Zn/Cu (60oC) 1.0 1.0 ? ?
25oC 40oC
Metal
pair
- ve
Conc CuSO4
+ve
Conc CuSO4
E
/V
Current/
A
Cu/Cu 1.0 1.0 ? ?
Cu/Cu 0.5 1.0 ? ?
Cu/Cu 0.25 1.0 ? ?
Cu/Cu 0.125 1.0 ? ?
Cu/Cu 0.0625 1.0 ? ?
1 M 1 M
-
-
-
-
-
-
-
-
+
+
+
+
+
+
+
+
0.5 M 1 M

6. 1
]1[
]1[
][
][
2
2

 

c
c
Q
M
M
Cu
Zn
Q
Zn half cell (-ve)
Oxidation
Cu half cell (+ve)
Reduction
Zn/Cu Cell
-e -e
Zn/Cu half cells
Std electrode potential as std reduction potential
Find Eθ
cell (use reduction potential)
Zn + Cu2+ → Zn2+ + Cu Eθ = ?????
Zn 2+ + 2e ↔ Zn Eθ = -0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/V
Li+ + e- ↔ Li -3.04
K+ + e- ↔ K -2.93
Ca2+ + 2e- ↔ Ca -2.87
Na+ + e- ↔ Na -2.71
Mg 2+ + 2e- ↔ Mg -2.37
Al3+ + 3e- ↔ AI -1.66
Mn2+ + 2e- ↔ Mn -1.19
H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76
Fe2+ + 2e- ↔ Fe -0.45
Ni2+ + 2e- ↔ Ni -0.26
Sn2+ + 2e- ↔ Sn -0.14
Pb2+ + 2e- ↔ Pb -0.13
H+ + e- ↔ 1/2H2 0.00
Cu2+ + e- ↔ Cu+ +0.15
SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.34
1/2O2 + H2O +2e- ↔ 2OH- +0.40
Cu+ + e- ↔ Cu +0.52
1/2I2 + e- ↔ I- +0.54
Fe3+ + e- ↔ Fe2+ +0.77
Ag+ + e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br- +1.07
1/2O2 + 2H+ +2e- ↔ H2O +1.23
Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.33
1/2CI2 + e- ↔ CI- +1.35
MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
-
-
-
-
Zn Cu
+
+
+
+
Std condition 1M
Q
nF
RT
EE ln 
Zn +Cu2+→Zn2++Cu E = ?
1M 1M
Zn2+
1 M 1 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10V
R = Gas constant (8.31)
n = # e transfer (2 e)
F = Faraday constant (96 500C mol -1 )







EE
VE
E
E
10.1
010.1
)1ln(
)965002(
)29831.8(
10.1
Std condition 1M

7. Zn half cell (-ve)
Oxidation
Cu half cell (+ve)
Reduction
Zn/Cu Cell
-e -e
Zn/Cu half cells
Std electrode potential as std reduction potential
Find Eθ
cell (use reduction potential)
Zn + Cu2+ → Zn2+ + Cu Eθ = ?????
Zn 2+ + 2e ↔ Zn Eθ = -0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/V
Li+ + e- ↔ Li -3.04
K+ + e- ↔ K -2.93
Ca2+ + 2e- ↔ Ca -2.87
Na+ + e- ↔ Na -2.71
Mg 2+ + 2e- ↔ Mg -2.37
Al3+ + 3e- ↔ AI -1.66
Mn2+ + 2e- ↔ Mn -1.19
H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76
Fe2+ + 2e- ↔ Fe -0.45
Ni2+ + 2e- ↔ Ni -0.26
Sn2+ + 2e- ↔ Sn -0.14
Pb2+ + 2e- ↔ Pb -0.13
H+ + e- ↔ 1/2H2 0.00
Cu2+ + e- ↔ Cu+ +0.15
SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.34
1/2O2 + H2O +2e- ↔ 2OH- +0.40
Cu+ + e- ↔ Cu +0.52
1/2I2 + e- ↔ I- +0.54
Fe3+ + e- ↔ Fe2+ +0.77
Ag+ + e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br- +1.07
1/2O2 + 2H+ +2e- ↔ H2O +1.23
Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.33
1/2CI2 + e- ↔ CI- +1.35
MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
-
-
-
-
Zn Cu
+
+
+
+
Std condition 1M
Q
nF
RT
EE ln 
Zn +Cu2+→Zn2++Cu E = ?
1M 0.1M
Zn2+
10
]1.0[
]1[
][
][
2
2

 

c
c
Q
M
M
Cu
Zn
Q
0.1 M 1 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10V
R = Gas constant (8.31)
n = # e transfer (2 e)
F = Faraday constant (96 500C mol -1 )
VE
E
E
07.1
03.010.1
)10ln(
)965002(
)29831.8(
10.1





Non std 0.1M
E cell decrease ↓ [Cu2+] decrease ↓
↓
Le Chatelier’s principle
↓
Cu2+ + 2e ↔ Cu
↓
[Cu2+] decrease ↓
↓
Shift to left ←
↓
E cell → less ↓ +ve → Cu2+ less able ↓ to receive e- / Cu more able ↑ to lose e-
[Cu2+] ↓ E cell < Eθ
1.07 < 1.10

8. Zn half cell (-ve)
Oxidation
Cu half cell (+ve)
Reduction
Zn/Cu Cell
-e -e
Zn/Cu half cells
Std electrode potential as std reduction potential
Find Eθ
cell (use reduction potential)
Zn + Cu2+ → Zn2+ + Cu Eθ = ?????
Zn 2+ + 2e ↔ Zn Eθ = -0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/V
Li+ + e- ↔ Li -3.04
K+ + e- ↔ K -2.93
Ca2+ + 2e- ↔ Ca -2.87
Na+ + e- ↔ Na -2.71
Mg 2+ + 2e- ↔ Mg -2.37
Al3+ + 3e- ↔ AI -1.66
Mn2+ + 2e- ↔ Mn -1.19
H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76
Fe2+ + 2e- ↔ Fe -0.45
Ni2+ + 2e- ↔ Ni -0.26
Sn2+ + 2e- ↔ Sn -0.14
Pb2+ + 2e- ↔ Pb -0.13
H+ + e- ↔ 1/2H2 0.00
Cu2+ + e- ↔ Cu+ +0.15
SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.34
1/2O2 + H2O +2e- ↔ 2OH- +0.40
Cu+ + e- ↔ Cu +0.52
1/2I2 + e- ↔ I- +0.54
Fe3+ + e- ↔ Fe2+ +0.77
Ag+ + e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br- +1.07
1/2O2 + 2H+ +2e- ↔ H2O +1.23
Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.33
1/2CI2 + e- ↔ CI- +1.35
MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
-
-
-
-
Zn Cu
+
+
+
+
Std condition 1M
Q
nF
RT
EE ln 
Zn +Cu2+→Zn2++Cu E = ?
1M 10M
Zn2+
1.0
]10[
]1[
][
][
2
2

 

c
c
Q
M
M
Cu
Zn
Q
10 M 1 M
Using Nernst Eqn
E0 =Std condition (1M) – 1.10V
R = Gas constant (8.31)
n = # e transfer (2 e)
F = Faraday constant (96 500C mol -1 )
VE
E
E
13.1
03.010.1
)1.0ln(
)965002(
)29831.8(
10.1





Non std 0.1M
E cell increase ↑ [Cu2+] increase ↑
↓
Le Chatelier’s principle
↓
Cu2+ + 2e ↔ Cu
↓
[Cu2+] increase ↑
↓
Shift to right →
↓
E cell → more ↑ +ve → Cu2+ more able receive e-
[Cu2+] ↑ E cell > Eθ
1.13 > 1.10

9. Zn half cell (-ve)
Oxidation
Cu half cell (+ve)
Reduction
Zn/Cu Cell
-e -e
Zn/Cu half cells
Std electrode potential as std reduction potential
Find Eθ
cell (use reduction potential)
Zn + Cu2+ → Zn2+ + Cu Eθ = ?????
Zn 2+ + 2e ↔ Zn Eθ = -0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/V
Li+ + e- ↔ Li -3.04
K+ + e- ↔ K -2.93
Ca2+ + 2e- ↔ Ca -2.87
Na+ + e- ↔ Na -2.71
Mg 2+ + 2e- ↔ Mg -2.37
Al3+ + 3e- ↔ AI -1.66
Mn2+ + 2e- ↔ Mn -1.19
H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76
Fe2+ + 2e- ↔ Fe -0.45
Ni2+ + 2e- ↔ Ni -0.26
Sn2+ + 2e- ↔ Sn -0.14
Pb2+ + 2e- ↔ Pb -0.13
H+ + e- ↔ 1/2H2 0.00
Cu2+ + e- ↔ Cu+ +0.15
SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.34
1/2O2 + H2O +2e- ↔ 2OH- +0.40
Cu+ + e- ↔ Cu +0.52
1/2I2 + e- ↔ I- +0.54
Fe3+ + e- ↔ Fe2+ +0.77
Ag+ + e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br- +1.07
1/2O2 + 2H+ +2e- ↔ H2O +1.23
Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.33
1/2CI2 + e- ↔ CI- +1.35
MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
-
-
-
-
Zn Cu
+
+
+
+
Std condition 1M
Q
nF
RT
EE ln 
Zn +Cu2+→Zn2++Cu E = ?
0.1M 1M
Zn2+
1.0
]1[
]1.0[
][
][
2
2

 

c
c
Q
M
M
Cu
Zn
Q
1 M 0.1 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10V
R = Gas constant (8.31)
n = # e transfer (2 e)
F = Faraday constant (96 500C mol -1 )
VE
E
E
13.1
03.010.1
)1.0ln(
)965002(
)29831.8(
10.1





Non std 0.1M
E cell increase ↑ [Zn2+] decrease ↓
↓
Le Chatelier’s principle
↓
Zn2+ + 2e ↔ Zn
↓
[Zn2+] decrease ↓
↓
Shift to left ←
↓
E cell → more ↑ +ve → Zn more able lose elec
[Zn2+] ↓ E cell > Eθ
1.13 > 1.10

10. Zn half cell (-ve)
Oxidation
Cu half cell (+ve)
Reduction
Zn/Cu Cell
-e -e
Zn/Cu half cells
Std electrode potential as std reduction potential
Find Eθ
cell (use reduction potential)
Zn + Cu2+ → Zn2+ + Cu Eθ = ?????
Zn 2+ + 2e ↔ Zn Eθ = -0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/V
Li+ + e- ↔ Li -3.04
K+ + e- ↔ K -2.93
Ca2+ + 2e- ↔ Ca -2.87
Na+ + e- ↔ Na -2.71
Mg 2+ + 2e- ↔ Mg -2.37
Al3+ + 3e- ↔ AI -1.66
Mn2+ + 2e- ↔ Mn -1.19
H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76
Fe2+ + 2e- ↔ Fe -0.45
Ni2+ + 2e- ↔ Ni -0.26
Sn2+ + 2e- ↔ Sn -0.14
Pb2+ + 2e- ↔ Pb -0.13
H+ + e- ↔ 1/2H2 0.00
Cu2+ + e- ↔ Cu+ +0.15
SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.34
1/2O2 + H2O +2e- ↔ 2OH- +0.40
Cu+ + e- ↔ Cu +0.52
1/2I2 + e- ↔ I- +0.54
Fe3+ + e- ↔ Fe2+ +0.77
Ag+ + e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br- +1.07
1/2O2 + 2H+ +2e- ↔ H2O +1.23
Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.33
1/2CI2 + e- ↔ CI- +1.35
MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
-
-
-
-
Zn Cu
+
+
+
+
Std condition 1M
Q
nF
RT
EE ln 
Zn +Cu2+→Zn2++Cu E = ?
10M 1M
Zn2+
10
]1[
]10[
][
][
2
2

 

c
c
Q
M
M
Cu
Zn
Q
1 M 10 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10V
R = Gas constant (8.31)
n = # e transfer (2 e)
F = Faraday constant (96 500C mol -1 )
VE
E
E
07.1
03.010.1
)10ln(
)965002(
)29831.8(
10.1





Non std 10M
E cell decrease ↓ [Zn2+] increase ↑
↓
Le Chatelier’s principle
↓
Zn2+ + 2e ↔ Zn
↓
[Zn2+] increase ↑
↓
Shift to right →
↓
E cell → less ↓ +ve → Zn less able ↓ lose e-
[Zn2+] ↑ E cell < Eθ
1.07 < 1.10

11. Zn half cell (-ve)
Oxidation
Cu half cell (+ve)
Reduction
Zn/Cu Cell
-e -e
Zn/Cu half cells
Std electrode potential as std reduction potential
Zn + Cu2+ → Zn2+ + Cu Eθ = ?
Zn 2+ + 2e ↔ Zn Eθ = -0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76V
Cu2+ + 2e ↔ Cu Eθ = +0.34V
Zn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/V
Li+ + e- ↔ Li -3.04
K+ + e- ↔ K -2.93
Ca2+ + 2e- ↔ Ca -2.87
Na+ + e- ↔ Na -2.71
Mg 2+ + 2e- ↔ Mg -2.37
Al3+ + 3e- ↔ AI -1.66
Mn2+ + 2e- ↔ Mn -1.19
H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76
Fe2+ + 2e- ↔ Fe -0.45
Ni2+ + 2e- ↔ Ni -0.26
Sn2+ + 2e- ↔ Sn -0.14
Pb2+ + 2e- ↔ Pb -0.13
H+ + e- ↔ 1/2H2 0.00
Cu2+ + e- ↔ Cu+ +0.15
SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.34
1/2O2 + H2O +2e- ↔ 2OH- +0.40
Cu+ + e- ↔ Cu +0.52
1/2I2 + e- ↔ I- +0.54
Fe3+ + e- ↔ Fe2+ +0.77
Ag+ + e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br- +1.07
1/2O2 + 2H+ +2e- ↔ H2O +1.23
Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.33
1/2CI2 + e- ↔ CI- +1.35
MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
-
-
-
-
Zn Cu
+
+
+
+
Std condition 1M
Q
nF
RT
EE ln 
Zn +Cu2+→Zn2++Cu E = ?
0.1M 10M
Zn2+
01.0
]10[
]1.0[
][
][
2
2

 

c
c
Q
M
M
Cu
Zn
Q
10 M 0.1 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10V
R = Gas constant (8.31)
n = # e transfer (2 e)
F = Faraday constant (96 500C mol -1 )
VE
E
E
16.1
059.010.1
)01.0ln(
)965002(
)29831.8(
10.1





Non std 0.1/10M
E cell increase ↑ [Zn2+] decrease ↓
↓
Le Chatelier’s principle
↓
Zn2+ + 2e ↔ Zn
↓
[Zn2+] decrease ↓
↓
Shift to left ←
↓
E → ↑ +ve → Zn more able lose e-
E cell increase ↑ [Cu2+] increase ↑
↓
Le Chatelier’s principle
↓
Cu2+ + 2e ↔ Cu
↓
[Cu2+] increase ↑
↓
Shift to right →
↓
E→↑ +ve → Cu2+ more able gain e-
+
[Zn2+] ↓/ [Cu2+] ↑E cell > Eθ
Very +ve 1.16 > 1.10

12. Eθ value DO NOT depend surface area of metal electrode.
E cell = Energy per unit charge. (Joule)/C
E cell- 10v = 10J energy released by 1C of charge flowing
= 100J energy released by 10C of charge flowing
Eθ – intensiveproperty–independentof amt – Ratio energy/charge
Increasing surface area metal will NOT increase E cell
Eθ
Zn/Cu = 1.10V
Surface area exposed 10 cm2
Total charges 100C leave electrode
E cell = 1.1V = 1.1 J energy for 1 C (charges leaving)
1C release 1.1 J energy
100 C release 110 J energy
Voltmetermeasure energy for 1C – 110J/100C – 1.1V
E cell no change
Current– measured in Amperes or Coulombs per second
1A = 1 Coulomb charge pass througha point in 1 second = 1C/s
1 Coulomb charge (electron)= 6.28 x 10 18 electronspassing in 1 second
1 electron/protoncarry charge of – 1.6 x 10 -19 C ( very small)
6.28 x 10 18 electron carry charge of - 1 C
ond
electron
ond
Coulomb
A
sec.1
.1028.6
sec1
1
1
18


Surface area increase ↑
Total Energy increase ↑
Total Charge increase ↑Current increase ↑
BUT E cell remainSAME
E cell = (Energy/charge)t
Q
I
tIQ


Q up ↑ – I up ↑
100C flow
110J released
VEcell
Ecell
eCh
Energy
Ecell
10.1
100
110
arg



Surfacearea exposed10 cm2
Surfacearea exposed100cm2
Surface area exposed 100 cm2
Total charges 1000C leave electrode
E cell = 1.1V = 1.1 J energy for 1 C (charges leaving)
1 C release 1.1J energy
1000 C release 1100 J energy
Voltmetermeasure energy for 1C – 1100J/1000C – 1.1V
E cell no change
VEcell
Ecell
eCh
Energy
Ecell
10.1
1000
1100
arg



Eθ
Zn/Cu = 1.10V
1000C flow
1100J released
t
Q
I 
t
Q
I 

13. Eθ value DO NOT depend surface area of metal electrode.
E cell = Energy per unit charge. (Joule)/C
E cell- 10v = 10J energy released by 1C of charge flowing
= 100J energy released by 10C of charge flowing
Eθ – intensiveproperty–independentof amt – Ratio energy/charge
Increasing surface area metal will NOT increase E cell
Eθ
Zn/Cu = 1.10V
Surface area exposed 10 cm2
Total charges 100C leave electrode
E cell = 1.1V = 1.1 J energy for 1 C (charges leaving)
1C release 1.1J energy
100 C release 110 J energy
Voltmetermeasure energy for 1C – 110J/100C – 1.1V
E cell no change
Surface area increase ↑
Total Energy increase ↑
Total Charge increase ↑Current increase ↑
BUT E cell remain SAME
E cell = (Energy/charge)t
Q
I
tIQ


Q up ↑ – I up ↑
100C flow
110J released
VEcell
Ecell
eCh
Energy
Ecell
10.1
100
110
arg



Surfacearea exposed10 cm2
Surfacearea exposed100cm2
Surface area exposed 100 cm2
Total charges 1000C leave electrode
E cell = 1.1V = 1.1 J energy for 1 C (charges leaving)
1 C release 1.1J energy
1000 C release 1100 J energy
Voltmetermeasure energy for 1C – 1100J/1000C – 1.1V
E cell no change
VEcell
Ecell
eCh
Energy
Ecell
10.1
1000
1100
arg



Eθ
Zn/Cu = 1.10V
1000C flow
1100J released
t
Q
I 
t
Q
I 
Q
nF
RT
EE ln 
Salt bridge conc
Conc of ion
E cell depend
Nature of electrode
Type of metal used Temp of sol
T = Temp in K
Q = Rxn Quotient
E0 = std (1M)
n = # e transfer
F = Faraday constant
(96 500C mol -1 )
R = Gas constant
(8.31)
Eθ Q T
E cell depend
Surface area
of contact
Size of
cation/anion

14. Eθ value DO NOT depend surface area of metal electrode.
E cell = Energy per unit charge. (Joule)/C
E cell- 10v = 10J energy released by 1C of charge flowing
= 100J energy released by 10C of charge flowing
Eθ – intensiveproperty–independentof amt – Ratio energy/charge
Increasing surface area metal will NOT increase E cell
Surface area increase ↑
Total Energy increase ↑
Total Charge increase ↑Current increase ↑
BUT E cell remain SAME
E cell = (Energy/charge)
t
Q
I
tIQ


Q up ↑ – I up ↑
Q
nF
RT
EE ln 
Salt bridge conc
Conc of ion
E cell depend
Nature of electrode
Type of metal used Temp of sol
T = Temp in K
Q = Rxn Quotient
E0 = std (1M)
n = # e transfer
F = Faraday constant
(96 500C mol -1 )
R = Gas constant
(8.31)
Eθ Q T
E cell depend
Salt bridge conc
Surface area
of contact
Size of
cation/anion
Current/I depend
Eθ cell = EMF in V (std condition)
Eθ = Show ease/tendency of species to accept/lose electron
Eθ = +ve std electrode potential
(strong oxidizing agent – weak reducing agent – accept e-)
Eθ = - ve std electrode potential
(strong reducing agent - weak oxidizing agent – lose e-)
Eθ = written as std reduction potential
Eθ DO NOT depend on stoichiometric coefficient.
EMF = Energy per unit charge. (Joule)/C
EMF 10v = 10J energy released by 1C charge
= 100J energy released by 10C charge
= 1000J energy released by 100C charge
Eθ = Intensive property – INDEPENDENT of amt
(Ratio energy/charge)
Eθ = +ve suggest rxn feasible, does not tell rate
(feasible but may be slow, give no indication rate)
Eθ = +ve = Energetically feasible but kinetically non feasible
Size of
cation/anion
Surface area
of contact
Resistance high ↑ – current low ↓
EMF = 10V