http://lawrencekok.blogspot.com
Prepared by Lawrence Kok
Tutorial on Design Experiment for Voltaic Cell and Nernst Equation.
Research Questions:• Effect Diff ZnSO4 / CuSO4 on emf /current in Voltaic CellResearch 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 termin
al
+ve termin
al
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 metal pairs on emf/current in Voltaic CellResearch Questions:• Effect Diff metal pairs 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 sol.• Measure emf and current of Mg/Cu cell•Repeat with diff metal pairs
Metal pair
ConcZnSO4
ConcCuSO4
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
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
ConcZnSO4
ConcCuSO4
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 CellResearch 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
ConcZnSO4
ConcCuSO4
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 CellResearch 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
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)
ConcZnSO
4
ConcCuSO
4
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 CellResearch 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 CellResearch Questions:• Effect Diff surface area on emf /current in Voltaic Cell
Cu2+
CuZn
Zn2+
Zn Cu
Zn2+ Cu2+
1 % 2 %
--
--
--
--
++ +
+
++
++
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 CellResearch 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 CellResearch Questions:• Effect Diff cation size on emf/current in Voltaic Cell
Cu2+
CuZn
Zn2+
Zn Cu
Zn2+ Cu2+
Cation size(salt bridge)
ConcZnSO
4
ConcCuSO4
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)
ConcZnSO
4
ConcCuSO4
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--
--
--
++
++
++
--
++
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 CellResearch 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 CellResearch Questions:• Effect Temp on emf/current in Voltaic Cell
Cu2+
CuZn
Zn2+
Cu Cu
Cu2+ Cu2+
Temp/C ConcZnSO
4
ConcCuSO4
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
- veConc
CuSO4
+veConc
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
1
]1[
]1[
][
][2
2
c
c
Q
M
M
Cu
ZnQ
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 Eθcell (use reduction potential)
Zn + Cu2+ → Zn2+ + Cu Eθ = ?????
Zn 2+ + 2e ↔ Zn Eθ = -0.76VCu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76VCu2+ + 2e ↔ Cu Eθ = +0.34VZn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40Cu+ + e- ↔ Cu +0.521/2I2 + e- ↔ I- +0.54Fe3+ + e- ↔ Fe2+ +0.77Ag+ + e- ↔ Ag +0.801/2Br2 + e- ↔ Br- +1.071/2O2 + 2H+ +2e- ↔ H2O +1.23Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.331/2CI2 + e- ↔ CI- +1.35MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.511/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
----
Zn Cu
++++
Std condition 1M
QnF
RTEE ln
Zn +Cu2+→Zn2++Cu E = ?
1M 1M
Zn2+
1 M 1 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10VR = 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
Zn half cell (-ve)Oxidation
Cu half cell (+ve)Reduction
Zn/Cu Cell
-e -eZn/Cu half cells
Std electrode potential as std reduction potential
Find Eθcell (use reduction potential)
Zn + Cu2+ → Zn2+ + Cu Eθ = ?????
Zn 2+ + 2e ↔ Zn Eθ = -0.76VCu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76VCu2+ + 2e ↔ Cu Eθ = +0.34VZn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40Cu+ + e- ↔ Cu +0.521/2I2 + e- ↔ I- +0.54Fe3+ + e- ↔ Fe2+ +0.77Ag+ + e- ↔ Ag +0.801/2Br2 + e- ↔ Br- +1.071/2O2 + 2H+ +2e- ↔ H2O +1.23Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.331/2CI2 + e- ↔ CI- +1.35MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.511/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
----
Zn Cu
++++
Std condition 1M
QnF
RTEE ln
Zn +Cu2+→Zn2++Cu E = ?
1M 0.1M
Zn2+
10
]1.0[
]1[
][
][2
2
c
c
Q
M
M
Cu
ZnQ
0.1 M 1 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10VR = 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
Zn half cell (-ve)Oxidation
Cu half cell (+ve)Reduction
Zn/Cu Cell
-e -eZn/Cu half cells
Std electrode potential as std reduction potential
Find Eθcell (use reduction potential)
Zn + Cu2+ → Zn2+ + Cu Eθ = ?????
Zn 2+ + 2e ↔ Zn Eθ = -0.76VCu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76VCu2+ + 2e ↔ Cu Eθ = +0.34VZn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40Cu+ + e- ↔ Cu +0.521/2I2 + e- ↔ I- +0.54Fe3+ + e- ↔ Fe2+ +0.77Ag+ + e- ↔ Ag +0.801/2Br2 + e- ↔ Br- +1.071/2O2 + 2H+ +2e- ↔ H2O +1.23Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.331/2CI2 + e- ↔ CI- +1.35MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.511/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
----
Zn Cu
++++
Std condition 1M
QnF
RTEE ln
Zn +Cu2+→Zn2++Cu E = ?
1M 10M
Zn2+
1.0
]10[
]1[
][
][2
2
c
c
Q
M
M
Cu
ZnQ
10 M 1 M
Using Nernst Eqn
E0 =Std condition (1M) – 1.10VR = 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
Zn half cell (-ve)Oxidation
Cu half cell (+ve)Reduction
Zn/Cu Cell
-e -eZn/Cu half cells
Std electrode potential as std reduction potential
Find Eθcell (use reduction potential)
Zn + Cu2+ → Zn2+ + Cu Eθ = ?????
Zn 2+ + 2e ↔ Zn Eθ = -0.76VCu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76VCu2+ + 2e ↔ Cu Eθ = +0.34VZn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40Cu+ + e- ↔ Cu +0.521/2I2 + e- ↔ I- +0.54Fe3+ + e- ↔ Fe2+ +0.77Ag+ + e- ↔ Ag +0.801/2Br2 + e- ↔ Br- +1.071/2O2 + 2H+ +2e- ↔ H2O +1.23Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.331/2CI2 + e- ↔ CI- +1.35MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.511/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
----
Zn Cu
++++
Std condition 1M
QnF
RTEE ln
Zn +Cu2+→Zn2++Cu E = ?
0.1M 1M
Zn2+
1.0
]1[
]1.0[
][
][2
2
c
c
Q
M
M
Cu
ZnQ
1 M 0.1 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10VR = 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
Zn half cell (-ve)Oxidation
Cu half cell (+ve)Reduction
Zn/Cu Cell
-e -eZn/Cu half cells
Std electrode potential as std reduction potential
Find Eθcell (use reduction potential)
Zn + Cu2+ → Zn2+ + Cu Eθ = ?????
Zn 2+ + 2e ↔ Zn Eθ = -0.76VCu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76VCu2+ + 2e ↔ Cu Eθ = +0.34VZn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40Cu+ + e- ↔ Cu +0.521/2I2 + e- ↔ I- +0.54Fe3+ + e- ↔ Fe2+ +0.77Ag+ + e- ↔ Ag +0.801/2Br2 + e- ↔ Br- +1.071/2O2 + 2H+ +2e- ↔ H2O +1.23Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.331/2CI2 + e- ↔ CI- +1.35MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.511/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
----
Zn Cu
++++
Std condition 1M
QnF
RTEE ln
Zn +Cu2+→Zn2++Cu E = ?
10M 1M
Zn2+
10
]1[
]10[
][
][2
2
c
c
Q
M
M
Cu
ZnQ
1 M 10 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10VR = 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
Zn half cell (-ve)Oxidation
Cu half cell (+ve)Reduction
Zn/Cu Cell
-e -eZn/Cu half cells
Std electrode potential as std reduction potential
Zn + Cu2+ → Zn2+ + Cu Eθ = ?
Zn 2+ + 2e ↔ Zn Eθ = -0.76VCu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76VCu2+ + 2e ↔ Cu Eθ = +0.34VZn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40Cu+ + e- ↔ Cu +0.521/2I2 + e- ↔ I- +0.54Fe3+ + e- ↔ Fe2+ +0.77Ag+ + e- ↔ Ag +0.801/2Br2 + e- ↔ Br- +1.071/2O2 + 2H+ +2e- ↔ H2O +1.23Cr2O7
2-+14H+ +6e- ↔ 2Cr3+ + 7H2O +1.331/2CI2 + e- ↔ CI- +1.35MnO4
- + 8H+ + 5e- ↔ Mn2+ + 4H2O +1.511/2F2 + e- ↔ F +2.87
+1.10 V
Cu2+
----
Zn Cu
++++
Std condition 1M
QnF
RTEE ln
Zn +Cu2+→Zn2++Cu E = ?
0.1M 10M
Zn2+
01.0
]10[
]1.0[
][
][2
2
c
c
Q
M
M
Cu
ZnQ
10 M 0.1 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10VR = 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- E cell = VERY +ve ↑
+
Eθ value DO NOT depend surface area of metal electrode.E cell = Energy per unit charge. (Joule)/CE cell- 10v = 10J energy released by 1C of charge flowing = 100J energy released by 10C of charge flowing Eθ – intensive property– independent of 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 electrodeE cell = 1.1V = 1.1 J energy for 1 C (charges leaving) 1C release 1.1 J energy100 C release 110 J energyVoltmeter measure energy for 1C – 110J/100C – 1.1VE cell no change
Current – measured in Amperes or Coulombs per second 1A = 1 Coulomb charge pass through a point in 1 second = 1C/s1 Coulomb charge (electron) = 6.28 x 10 18 electrons passing in 1 second
1 electron/proton carry charge of – 1.6 x 10 -19 C ( very small)6.28 x 10 18 electron carry charge of - 1 C
ond
electron
ond
CoulombA
sec.1
.1028.6
sec1
11
18
Surface area increase ↑
Total Energy increase ↑
Total Charge increase ↑ Current increase ↑
BUT E cell remain SAMEE cell = (Energy/charge)t
QI
tIQ
Q up ↑ – I up ↑
100C flow
110J released
VEcell
Ecell
eCh
EnergyEcell
10.1100
110
arg
Surface area exposed 10 cm2
Surface area exposed 100cm2
Surface area exposed 100 cm2 Total charges 1000C leave electrodeE cell = 1.1V = 1.1 J energy for 1 C (charges leaving) 1 C release 1.1J energy1000 C release 1100 J energyVoltmeter measure energy for 1C – 1100J/1000C – 1.1VE cell no change
VEcell
Ecell
eCh
EnergyEcell
10.11000
1100
arg
Eθ Zn/Cu = 1.10V
1000C flow
1100J released
t
QI
t
QI
Eθ value DO NOT depend surface area of metal electrode.E cell = Energy per unit charge. (Joule)/CE cell- 10v = 10J energy released by 1C of charge flowing = 100J energy released by 10C of charge flowing Eθ – intensive property– independent of amt – Ratio energy/chargeIncreasing surface area metal will NOT increase E cell
Eθ Zn/Cu = 1.10V
Surface area exposed 10 cm2 Total charges 100C leave electrodeE cell = 1.1V = 1.1 J energy for 1 C (charges leaving) 1C release 1.1J energy100 C release 110 J energyVoltmeter measure energy for 1C – 110J/100C – 1.1VE cell no change
Surface area increase ↑
Total Energy increase ↑
Total Charge increase ↑ Current increase ↑
BUT E cell remain SAMEE cell = (Energy/charge)t
QI
tIQ
Q up ↑ – I up ↑
100C flow
110J released
VEcell
Ecell
eCh
EnergyEcell
10.1100
110
arg
Surface area exposed 10 cm2
Surface area exposed 100cm2
Surface area exposed 100 cm2 Total charges 1000C leave electrodeE cell = 1.1V = 1.1 J energy for 1 C (charges leaving) 1 C release 1.1J energy1000 C release 1100 J energyVoltmeter measure energy for 1C – 1100J/1000C – 1.1VE cell no change
VEcell
Ecell
eCh
EnergyEcell
10.11000
1100
arg
Eθ Zn/Cu = 1.10V
1000C flow
1100J released
t
QI
t
QI
QnF
RTEE ln
Salt bridge conc
Conc of ion
E cell depend
Nature of electrodeType of metal used Temp of sol
T = Temp in KQ = 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
Eθ value DO NOT depend surface area of metal electrode.E cell = Energy per unit charge. (Joule)/CE cell- 10v = 10J energy released by 1C of charge flowing = 100J energy released by 10C of charge flowing Eθ – intensive property–independent of 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 SAMEE cell = (Energy/charge)t
QI
tIQ
Q up ↑ – I up ↑Q
nF
RTEE ln
Salt bridge conc
Conc of ion
E cell depend
Nature of electrodeType of metal used Temp of sol
T = Temp in KQ = 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 electronEθ = +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 potentialEθ DO NOT depend on stoichiometric coefficient. EMF = Energy per unit charge. (Joule)/CEMF 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
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/http://spmchemistry.onlinetuition.com.my/2013/10/electrolytic-cell.htmlhttp://www.chemguide.co.uk/physical/redoxeqia/introduction.htmlhttp://educationia.tk/reduction-potential-tablehttp://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/s23-electrochemistry.html
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttp://lawrencekok.blogspot.com