ib chemistry on standard electrode potential, electrochemical series and emf for voltaic cell

http://lawrencekok.blogspot.com

Prepared by Lawrence Kok

Video Tutorial on Standard Electrode Potential, Voltaic Cell and Electrochemical Series.

http://lawrencekok.blogspot.com/


Aluminium air battery Excellent Zn/Cu gravity cell for IA Zinc air battery

Zn/Cu voltaic cell Zn/Cu voltaic cell

Video on Standard Electrode Potential and Voltaic Cell

http://www.youtube.com/watch?v=_FxIzMwOF00&feature=relmfu

http://www.youtube.com/watch?v=Id3tL2iI0Vw&feature=plcp&context=C3771c9aUDOEgsToPDskKAN3386D7q32JwAN3AMw53

http://www.youtube.com/watch?v=OcGWbt1mcrc&feature=plcp&context=C3b22d58UDOEgsToPDskI9rxobZyZ1mrYIjJfH9eSD

http://www.youtube.com/watch?v=raOj8QGDkPA&feature=related

http://www.youtube.com/watch?v=mrOm6xZip6k&feature=related

STRONG Reducing Agent

WEAK Reducing Agent

WEAK Oxidising Agent

STRONG Oxidising Agent

Electrochemical Series• Shows the ease/tendency of species to accept/lose electrons• Written as standard reduction potential


WEAK Reducing Agent



• Species on TOP right• High ↑tendency to lose e• Li → Li + + e• Eθ Li = +3.04V• STRONG reducing Agent• Oxidation favourable

• Species on BOTTOM right• Low ↓tendency to lose e• F - →1/2F2 + e• Eθ F2 = -2.87V• WEAK reducing Agent• Oxidation NOT favourable



WEAK Reducing Agent



• Species on TOP left• Low ↓ tendency to gain e• Li+ + e → Li• Eθ Li= - 3.04V• WEAK oxidising Agent• Reduction NOT favourable


• Species on BOTTOM left• High ↑ tendency to gain e• F2 + 2e → 2F-

• Eθ F2= +2.87V• STRONG oxidising Agent• Reduction favourable



Voltaic Cell for Zn/Cu electrode

Copper reduction Half Cell Zinc oxidation Half Cell

Cell Diagram for Zn/Cu half cellsElectrode/electrolyte ║ Electrolyte/electrode (-ve)/oxidation ║ (+ve)/reduction Zn/Zn2+ ║ Cu 2+/Cu

Determine Eθcell using std electrode potential and formula Eθ

cell = Eθ (+ve) - E

θ (-ve)

Voltaic Cell for Zn/Cu electrode

Copper reduction Half Cell Zinc oxidation Half Cell

Eθcell = Eθ

(+ve) - Eθ

(-ve)

Eθcell = Eθ

(cathode) (red) - Eθ

(anode)(oxi)

Eθcell = Eθ

(Cu) - Eθ

(Zn)

= 0.34 – (-0.76)

= +1.10V

Zn2+ + 2e → Zn Eθcell = -0.76V (Reduction potential)

Cu2+ + 2e → Cu Eθcell = +0.34V (Reduction potential)

Zn → Zn 2+ + 2e Eθ(Zn) (Oxidation potential)

Cu 2+ + 2e → Cu Eθ (Cu) (Reduction potential)

Zn + Cu 2+ → Cu + Zn 2+ Eθcell + 1.10V

Cell Diagram for Zn/Cu half cellsElectrode/electrolyte ║ Electrolyte/electrode (-ve)/oxidation ║ (+ve)/reduction Zn/Zn2+ ║ Cu 2+/Cu



θ (-ve)

Voltaic Cell for Mg/Fe electrode

Iron reduction Half Cell

Cell Diagram for Mg/Fe half cellsElectrode/electrolyte ║ Electrolyte/electrode (-ve)/oxidation ║ (+ve)/reduction Mg/Mg2+ ║ Fe2+/Fe



θ (-ve)

Magnesium oxidation Half Cell

Voltaic Cell for Mg/Fe electrode

Iron reduction Half Cell

Eθcell = Eθ

(+ve) - Eθ

(-ve)

Eθcell = Eθ

(cathode) (red) - Eθ

(anode) (oxi)

Eθcell = Eθ

(Fe) - Eθ

(Mg)

= 0.44 – (-2.36)

= +1.92V

Mg2+ + 2e → Mg Eθcell = -2.36V (Reduction potential)

Fe2+ + 2e → Fe Eθcell = +0.44V (Reduction potential)

Mg → Mg 2+ + 2e Eθ(Mg) (Oxidation potential)

Fe 2+ + 2e → Fe Eθ (Fe) (Reduction potential)

Mg + Fe2+ → Fe + Mg2+ Eθcell = + 1.92V

Cell Diagram for Mg/Fe half cellsElectrode/electrolyte ║ Electrolyte/electrode (-ve)/oxidation ║ (+ve)/reduction Mg/Mg2+ ║ Fe2+/Fe



θ (-ve)

Magnesium oxidation Half Cell


WEAK Reducing Agent



• Species on TOP left• Low ↓ tendency to gain e• Li+ + e → Li• Eθ Li= - 3.04V• WEAK oxidising Agent• Reduction NOT favourable


• Species on BOTTOM left• High ↑ tendency to gain e• F2 + 2e → 2F-

• Eθ F2= +2.87V• STRONG oxidising Agent• Reduction favourable



Steps to follow1. Species on top right / Eθ = (-ve) are Strong Reducing Agent (RA)2. Species on bottom left/ Eθ = (+ve) are Strong Oxidising Agent (OA)3. For a redox reaction to happen, choose• One (OA) from left• One (RA) from right4. Arrange the redox couple in order of their Eθ values • Eθ = (-ve) on top• Eθ = (+ve) at bottom5. Follow the anticlockwise rule or Z rule

Reaction between Zn + Cu2+ is possible (spontaneous)Zn is strong RA on the right• Undergo oxidation Zn → Zn2+ + 2eCu 2+ is strong OA on the left• Undergo reduction Cu2+ +2e → Cu• Z rule is followed and Eθ

Cell is (+ve)• Zn + Cu2+ → Zn2+ +Cu

Using Standard Electrode Potential to compare the strength of Oxidising/Reducing agents

Is reaction between Zn + Cu2+ possible (spontaneous) ?

Steps to follow1. Species on top right / Eθ = (-ve) are Strong Reducing Agent (RA)2. Species on bottom left/ Eθ = (+ve) are Strong Oxidising Agent (OA)3. For a redox reaction to happen, choose• One (OA) from left• One (RA) from right4. Arrange the redox couple in order of their Eθ values • Eθ = (-ve) on top• Eθ = (+ve) at bottom5. Follow the anticlockwise rule or Z rule

Reaction between Zn + Cu2+ is possible (spontaneous)Zn is strong RA on the right• Undergo oxidation Zn → Zn2+ + 2eCu 2+ is strong OA on the left• Undergo reduction Cu2+ +2e → Cu• Z rule is followed and Eθ

Cell is (+ve)• Zn + Cu2+ → Zn2+ +Cu

Using Standard Electrode Potential to compare the strength of Oxidising/Reducing agents


Eθ Cell calculation

Zn → Zn 2+ + 2e Eθ(Zn) = +0.76V (Oxidation potential)

Cu 2+ + 2e → Cu Eθ (Cu) = +.34V (Reduction potential)

Zn + Cu 2+ → Cu + Zn 2+ Eθcell = + 1.10V

SPONTANEOUS

Using Standard Electrode Potential to predict if reaction between Zn + Cu2+ is possible

Reaction between Zn + Cu2+ is spontaneousZn is strong RA on the right• Undergo oxidation Zn → Zn2+ + 2eCu 2+ is strong OA on the left• Undergo reduction Cu2+ +2e → Cu• Z rule is followed and Eθ

Cell is (+ve)• Zn + Cu2+ → Zn2+ + Cu


Using Standard Electrode Potential to predict if reaction between Mg + Cu2+ is possible

Reaction between Mg + Cu2+ is spontaneousMg is strong RA on the right• Undergo oxidation Mg → Mg2+ + 2eCu2+ is strong OA on the left• Undergo reduction Cu2+ +2e → Cu• Z rule is followed and Eθ

Cell is (+ve)• Mg + Cu2+ → Mg2+ + Cu

Is reaction between Mg + Cu2+ possible (spontaneous) ?

Using Standard Electrode Potential to predict if reaction between Zn + Cu2+ is possible

Reaction between Zn + Cu2+ is spontaneousZn is strong RA on the right• Undergo oxidation Zn → Zn2+ + 2eCu 2+ is strong OA on the left• Undergo reduction Cu2+ +2e → Cu• Z rule is followed and Eθ

Cell is (+ve)• Zn + Cu2+ → Zn2+ + Cu


Zn → Zn 2+ + 2e Eθ(Zn) = +0.76V (Oxidation potential)

Cu 2+ + 2e → Cu Eθ (Cu) = +.34V (Reduction potential)

Zn + Cu 2+ → Cu + Zn 2+ Eθcell = + 1.10V

EθCell calculation

Using Standard Electrode Potential to predict if reaction between Mg + Cu2+ is possible

Reaction between Mg + Cu2+ is spontaneousMg is strong RA on the right• Undergo oxidation Mg → Mg2+ + 2eCu2+ is strong OA on the left• Undergo reduction Cu2+ +2e → Cu• Z rule is followed and Eθ

Cell is (+ve)• Mg + Cu2+ → Mg2+ + Cu


Mg → Mg2+ + 2e Eθ(Mg) = +2.37V (Oxidation potential)

Cu 2+ + 2e → Cu Eθ (Cu) = +0.34V (Reduction potential)

Mg + Cu2+ → Cu + Mg2+ Eθcell = + 2.71V

Is reaction between Mg + Cu2+ possible (spontaneous) ?

SPONTANEOUS

SPONTANEOUS

Using Standard Electrode Potential to predict if reaction between Ag + Zn2+ is possible

Reaction between Ag + Zn2+ is NOT spontaneousAg is weak RA on the right• Undergo oxidation Ag → Ag+ + eZn2+ is weak OA on the left• Undergo reduction Zn2+ + 2e → Zn• Z rule is NOT X followed and Eθ

Cell is (-ve)• Ag + Zn2+ → Zn2+ +Cu Х

Is reaction between Ag + Zn2+ possible (spontaneous) ?

Using Standard Electrode Potential to predict if reaction between Fe3+ + CI - is possible

Reaction between Fe3+ + CI - is NOT spontaneous CI - is weak RA on the right• Undergo oxidation 2CI - → CI2 + 2eFe3+ is weak OA on the left• Undergo reduction Fe3+ +e → Fe2+

• Z rule is NOT X followed and Eθ Cell is (-ve)

• Fe3+ + 2CI - → Fe2+ +CI2 Х

Is reaction between Fe3+ + CI - possible (spontaneous) ?

Using Standard Electrode Potential to predict if reaction between Ag + Zn2+ is possible

Reaction between Ag + Zn2+ is NOT spontaneousAg is weak RA on the right• Undergo oxidation Ag → Ag+ + eZn2+ is weak OA on the left• Undergo reduction Zn2+ + 2e → Zn• Z rule is NOT X followed and Eθ

Cell is (-ve)• Ag + Zn2+ → Zn2+ +Cu Х

Is reaction between Ag + Zn2+ possible (spontaneous) ?

Ag → Ag+ + e Eθ(Ag) = -0.80V (Oxidation potential)

Zn2+ + 2e → Zn Eθ (Zn) = -0.76V (Reduction potential)

Ag + Zn2+ → Zn + Ag+ Eθcell = -1.56V


Using Standard Electrode Potential to predict if reaction between Fe3+ + CI - is possible

Reaction between Fe3+ + CI - is NOT spontaneous CI - is weak RA on the right• Undergo oxidation 2CI - → CI2 + 2eFe3+ is weak OA on the left• Undergo reduction Fe3+ +e → Fe2+


• Fe3+ + 2CI - → Fe2+ +CI2 Х


2CI - → CI2 + 2e Eθ(CI) = -1.36V (Oxidation potential)

Fe3+ + e → Fe2+ Eθ (Fe) = +0.77V (Reduction potential)

2CI - + Fe3+ → CI2 + Fe2+ Eθcell = -0.59V

Is reaction between Fe3+ + CI - possible (spontaneous) ?

NON SPONTANEOUS

NON SPONTANEOUS

Using Standard Electrode Potential to predict if reaction between AI + H+ is possible

Reaction between AI + H+ (HCI) is spontaneousAI is strong RA on the right• Undergo oxidation AI → AI3+ + 3eH+ is strong OA on the left• Undergo reduction 2H+ + 2e → H2

• Z rule is followed and EθCell is (+ve)

• AI + 2H+ → Al3+ + H2

Is reaction between AI + H+ possible (spontaneous) ?

Using Standard Electrode Potential to predict if reaction between Cu + H + is possible

Reaction between Cu + H + (HCI) is NOT spontaneous Cu is weak RA on the right• Undergo oxidation Cu → Cu2+ + 2eH+ is weak OA on the left• Undergo reduction 2H+ + 2e → H2

• Z rule is NOT X followed and EθCell is (-ve)

• Cu + 2H + → Cu2+ +H2 X

Is reaction between Cu + H+ possible (spontaneous) ?

Using Standard Electrode Potential to predict if reaction between AI + H+ is possible

Reaction between AI + H+ (HCI) is spontaneousAI is strong RA on the right• Undergo oxidation AI → AI3+ + 3eH+ is strong OA on the left• Undergo reduction 2H+ + 2e → H2


• AI + 2H+ → Al3+ + H2

Is reaction between AI + H+ possible (spontaneous) ?

AI → AI3+ + 3e Eθ(AI) = +1.66V (Oxidation potential)

2H+ + 2e → H2 Eθ

(H2) = 0.00V (Reduction potential)

AI + 2H+ → AI3+ + H2 Eθ

cell = +1.66V


Using Standard Electrode Potential to predict if reaction between Cu + H + is possible

Reaction between Cu + H + (HCI) is NOT spontaneous Cu is weak RA on the right• Undergo oxidation Cu → Cu2+ + 2eH+ is weak OA on the left• Undergo reduction 2H+ + 2e → H2

• Z rule is NOT X followed and EθCell is (-ve)

• Cu + 2H + → Cu2+ +H2 Х


Cu → Cu2+ + 2e Eθ(Cu) = -0.34V (Oxidation potential)

2H+ + 2e → H2 Eθ

(H2) = +0.00V (Reduction potential)

Cu + 2H+ → H2 + Cu2+ Eθcell = -0.34V

Is reaction between Cu + H+ possible (spontaneous) ?

NON SPONTANEOUS

SPONTANEOUS

Using Standard Electrode Potential to predict reaction between halogens and halides

Will Chlorine oxidise bromide to bromine ? (Cl2 + Br - → CI - + Br2)Will Bromine oxidise iodide to iodine ? (Br2 + I - → Br - + I2 )Will Iodine oxidise chloride to chlorine ? (I2 + CI - → I - + CI2)

Steps to follow1. Arrange standard electrode potential in order shown below (Highest Eθ = +ve at bottom)

2. Pick one (OA) and one (RA) from both sides and follow Z rule

Reaction between Cl2 + 2I - → CI - + I2 is spontaneousI - is strong RA on the right• Undergo oxidation 2I - → I2 + 2eCI2

is strong OA on the left• Undergo reduction CI2 + 2e → 2CI -


• Cl2 + 2I - → CI - + I2

Is reaction between CI2 + I - possible (spontaneous) ?

Highest Eθ (+ve) at the bottom

Using Standard Electrode Potential to predict reaction between halogens and halides

Will Chlorine oxidise bromide to bromine ? (Cl2 + Br - → CI - + Br2)Will Bromine oxidise iodide to iodine ? (Br2 + I - → Br - + I2 )Will Iodine oxidise chloride to chlorine ? (I2 + CI - → I - + CI2)

Steps to follow1. Arrange standard electrode potential in order shown below (Highest Eθ = +ve at bottom)

2. Pick one (OA) and one (RA) from both sides and follow Z rule




• Cl2 + 2I - → CI - + I2


2I - → I2 + 2e Eθ(I2) = -0.54V (Oxidation potential)

CI2 + 2e → 2CI - Eθ (CI2) = +1.33V (Reduction potential)

Cl2 + 2I - → CI -+ I2 Eθ

cell = +0.79V


Highest Eθ (+ve) at the bottom

SPONTANEOUS

Using Standard Electrode Potential to predict if reaction between CI2 + I - is possible




• Cl2 + 2I - → CI - + I2


Using Standard Electrode Potential to predict if reaction between Br2 + I - is possible

Reaction between Br2 + 2I - → 2Br - + I2 is spontaneousI - is strong RA on the right• Undergo oxidation 2I - → I2 + 2eBr2

is strong OA on the left• Undergo reduction Br2 + 2e → 2Br -

• Z rule is followed and Eθ Cell s (+ve)

• Br2 + 2I - → 2Br - + I2

Is reaction between Br2 + I - possible (spontaneous) ?

Using Standard Electrode Potential to predict if reaction between CI2 + I - is possible




• Cl2 + 2I - → CI - + I2



CI2 + 2e → 2CI - Eθ (CI2) = +1.33V (Reduction potential)

Cl2 + 2I - → CI -+ I2 Eθ

cell = +0.79VUsing Standard Electrode Potential to predict if reaction between Br2 + I - is possible

Reaction between Br2 + 2I - → 2Br - + I2 is spontaneousI - is strong RA on the right• Undergo oxidation 2I - → I2 + 2eBr2

is strong OA on the left• Undergo reduction Br2 + 2e → 2Br -

• Z rule is followed and Eθ Cell s (+ve)

• Br2 + 2I - → 2Br - + I2


Br2 + 2e → 2Br - Eθ(Br2) = +1.07V (Reduction potential)

Br2 + 2I - → 2Br - + I2 Eθ

cell = +0.53V

Is reaction between Br2 + I - possible (spontaneous) ?



SPONTANEOUS

SPONTANEOUS

Using Standard Electrode Potential to predict if reaction between I2 + CI - possible

Reaction between I2 + 2CI - → 2I - + CI2 NOT spontaneousCI - is weak RA on the right• Undergo oxidation 2CI - →CI2 + 2eI2

is weak OA on the left• Undergo reduction I2 + 2e → 2I -


• I2 + 2CI - → 2I - + CI2

Is reaction between I2 + CI - possible (spontaneous) ?

Using Standard Electrode Potential to predict if reaction between I2 + CI2 possible

Reaction between I2 + CI2 is NOT spontaneous• CANNOT have TWO species on the same side• Z rule is NOT X followed and Eθ

Cell is (-ve)

Is reaction between I2 + CI2 possible (spontaneous) ?

Using Standard Electrode Potential to predict if reaction between I2 + CI - possible

Reaction between I2 + 2CI - → 2I - + CI2 NOT spontaneousCI - is weak RA on the right• Undergo oxidation 2CI - →CI2 + 2eI2

is weak OA on the left• Undergo reduction I2 + 2e → 2I -


• I2 + 2CI - → 2I - + CI2

Is reaction between I2 + CI - possible (spontaneous) ?

2CI - → CI2 + 2e Eθ(CI2) = -1.33V (Oxidation potential)

I2 + 2e → 2I - Eθ (I2) = +0.54V (Reduction potential)

I2 + 2CI - → 2I - + CI2 Eθ

cell = -0.79V

Using Standard Electrode Potential to predict if reaction between I2 + CI2 possible

Reaction between I2 + CI2 is NOT spontaneous• CANNOT have TWO species on the same side• Z rule is NOT X followed and Eθ

Cell is (-ve)

Is reaction between I2 + CI2 possible (spontaneous) ?


NON SPONTANEOUS

NON SPONTANEOUS

Calculate the Eθ or emf for the following cells

Reaction between Mg + Sn2+ is spontaneousMg is strong RA on the right• Undergo oxidation Mg → Mg2+ + 2eSn2+ is strong OA on the left• Undergo reduction Sn2+ + 2e → Sn• Z rule is followed and Eθ

Cell is (+ve)• Mg + Sn2+ → Mg2+ + Sn

Reaction between Mg + Sn2+ Mg/Mg2+ ║ Sn2+/Sn

Reaction between Fe2+ + MnO4 -

Reaction between Fe2+ + CI - is spontaneous Fe 2+ is strong RA on the right• Undergo oxidation Fe2+ → Fe3+ + e MnO4

- is strong OA on the left• Undergo reduction MnO4

- + 8H+ + 5e → Mn2+ + 4H2O• Z rule is followed and Eθ

Cell is (+ve)• 2MnO4

- + 5Fe2+ + 8H+ → 5Fe3+ + Mn2+ + 4H2O

Fe2+/Fe3+ ║ MnO4 -/Mn2+

Calculate the Eθ or emf for the following cells

Reaction between Mg + Sn2+ is spontaneousMg is strong RA on the right• Undergo oxidation Mg → Mg2+ + 2eSn2+ is strong OA on the left• Undergo reduction Sn2+ + 2e → Sn• Z rule is followed and Eθ

Cell is (+ve)• Mg + Sn2+ → Mg2+ + Sn

Reaction between Mg + Sn2+

Fe 2+ → Fe3+ + e Eθ(Fe) = -0.777V (Oxidation potential)

MnO4 - + 8H+ + 5e → Mn2+ + 4H2O Eθ

(Mn) = +1.51V (Reduction potential)

2MnO4 -+ 5Fe2+ + 8H+ → 5Fe3+ + Mn2++4H2O Eθ

cell = +0.75V


Mg/Mg2+ ║ Sn2+/Sn

Reaction between Fe2+ + MnO4 -

Reaction between Fe2+ + CI - is spontaneous Fe 2+ is strong RA on the right• Undergo oxidation Fe2+ → Fe3+ + e MnO4

- is strong OA on the left• Undergo reduction MnO4

- + 8H+ + 5e → Mn2+ + 4H2O• Z rule is followed and Eθ

Cell is (+ve)• 2MnO4

- + 5Fe2+ + 8H+ → 5Fe3+ + Mn2+ + 4H2O

Mg → Mg2+ + 2e Eθ(Mg) = +2.37V (Oxidation potential)

Sn 2+ + 2e → Sn Eθ(Sn) = -0.14V (Reduction potential)

Mg + Sn2+ → Mg2+ + Sn Eθcell = + 2.23V


Fe2+/Fe3+ ║ MnO4 -/Mn2+

SPONTANEOUS

SPONTANEOUS

Is the reaction between Ag + AI3+ → Ag+ + AI possible ?

Reaction between Ag + AI3+ is NOT spontaneousAg is weak RA on the right• Undergo oxidation Ag → Ag+ + eAl3+ is weak OA on the left• Undergo reduction AI3+ + 3e → Al• Z rule is NOT X followed and Eθ

Cell is (-ve)• Ag + AI3+ → Ag+ + AI

Reaction between Ag + Al3+


Ag → Ag+ + e Eθ(Ag) = -0.80V (Oxidation potential)

AI3+ + 3e → AI Eθ(AI) = -1.66V (Reduction potential)

Ag + AI3+ → Ag+ + AI Eθcell = -2.46V

NONSPONTANEOUS

Acknowledgements

Thanks to source of pictures and video used in this presentation

Thanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/

Prepared by Lawrence Kok

Check out more video tutorials from my site and hope you enjoy this tutorialhttp://lawrencekok.blogspot.com

http://creativecommons.org/licenses/


ib chemistry on standard electrode potential, electrochemical series and emf for voltaic cell

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