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Electrochemistry Lesson 7 The Standard Hydrogen Cell. The Standard Hydrogen Half Cell The zero point of the reduction chart is the hydrogen half-cell. E is the cell potential or voltage E 0 is the standard cell potential @ 25 o C solutions are 1.0 M gases are 101 KPa. - PowerPoint PPT Presentation
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ElectrochemistryLesson 7
The StandardHydrogen Cell
The Standard Hydrogen Half Cell
The zero point of the reduction chart is the hydrogen half-cell.
E is the cell potential or voltage
E0 is the standard cell potential @ 25 oCsolutions are 1.0 Mgases are 101 KPa
Ag+ reacts with H2 spontaneously Eo = +0.80 v
Zn2+ is nonspontaneous with H2 Eo = -0.76 v
All half reactions are compared to H2
The voltage for any combination is the difference
Using the Reduction Potential Chart
Look on your reduction chart to find the voltage of each agent. Oxidizing agents are on the left and reducing agents are on the right. Formula Agent Type E0
HClO4 oxidizing
Using the Reduction Potential Chart
Look on your reduction chart to find the voltage of each agent. Oxidizing agents are on the left and reducing agents are on the right. Formula Agent Type E0
ClO4
- Acid oxidizing 1.39 v
HNO3 oxidizing
Take higher oneStronger Oxidizing Agent
HNO3 is both H+ and NO3
-
Using the Reduction Potential Chart
Look on your reduction chart to find the voltage of each agent. Oxidizing agents are on the left and reducing agents are on the right. Formula Agent Type E0
ClO4
- Acid oxidizing 1.39 v
HNO3 oxidizing 0.96 v
HCl oxidizing
Using the Reduction Potential Chart
Look on your reduction chart to find the voltage of each agent. Oxidizing agents are on the left and reducing agents are on the right. Formula Agent Type E0
ClO4
- Acid oxidizing 1.39 v
HNO3 oxidizing 0.96 v
HCl oxidizing 0.00 vSO4
2- reducing
The reaction is reversed so the E0 = -2.01 v
Oxidation
Using the Reduction Potential Chart
Look on your reduction chart to find the voltage of each agent. Oxidizing agents are on the left and reducing agents are on the right. Formula Agent Type E0
ClO4
- Acid oxidizing 1.39 v
HNO3 oxidizing 0.96 v
HCl oxidizing 0.00 vSO4
2- reducing -2.01 v
MnO4- Acid oxidizing
Using the Reduction Potential Chart
Look on your reduction chart to find the voltage of each agent. Oxidizing agents are on the left and reducing agents are on the right. Formula Agent Type E0
ClO4
- Acid oxidizing 1.39 v
HNO3 oxidizing 0.96 v
HCl oxidizing 0.00 v SO4
2- reducing -2.01 v
MnO4- Acid oxidizing 1.51 v
MnO4- Alkaline oxidizing
Using the Reduction Potential Chart
Look on your reduction chart to find the voltage of each agent. Oxidizing agents are on the left and reducing agents are on the right. Formula Agent Type E0
ClO4
- Acid oxidizing 1.39 v
HNO3 oxidizing 0.96 v
HCl oxidizing 0.00 vSO4
2- reducing -2.01 v
MnO4- Acid oxidizing 1.51 v
MnO4- Alkaline oxidizing 0.60 v
Formula Agent Type E0
H2SO4 oxidizing
H2SO4 → HSO4- + H+
Don’t have SO42-
Formula Agent Type E0
H2SO4 oxidizing 0.00 v
H2O Neutral oxidizing
Formula Agent Type E0
H2SO4 oxidizing 0.00 v
H2O Neutral oxidizing -0.41 v
H2O Neutral reducing
Formula Agent Type E0
H2SO4 oxidizing 0.00 v
H2O Neutral oxidizing -0.41 v
H2O Neutral reducing -0.82 v
Fe2+ reducing
Formula Agent Type E0
H2SO4 oxidizing 0.00 v
H2O Neutral oxidizing -0.41 v
H2O Neutral reducing -0.82 v
Fe2+ reducing -0.77 v
Fe2+ oxidizing
Formula Agent Type E0
H2SO4 oxidizing 0.00 v
H2O Neutral oxidizing -0.41 v
H2O Neutral reducing -0.82 v
Fe2+ reducing -0.77 v
Fe2+ oxidizing -0.45 v
Determine if the reaction below is spontaneous. Write a balanced equation for the reaction and calculate the E0. 1. MnO4
- & Mn2+ Acid
Reduction
Oxidation
The top reaction is written forward
The bottom reaction is reversed and the voltage is changed to negative
Determine if the reaction below is spontaneous. Write a balanced equation for the reaction and calculate the E0. 1. MnO4
- & Mn2+ Acid
2(MnO4- + 8H+ + 5e-→ Mn2+ + 4H2O) 1.51 v
5(Mn2+ + 2H2O → MnO2(s)+ 4H+ + 2e-) -1.22 v
2MnO4-+16H++5Mn2++10H2O → 2Mn2++8H2O+5MnO2(s)+20H+
2MnO4- + 3Mn2+ + 2H2O → 5MnO2(s) + 4H+ 0.29 v
add potentials
40.29 v
3 2
simplify
positive voltage- spontaneous