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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

E0 is the standard cell potential
@ 25 oC
solutions are 1.0 M
gases are 101 KPa
All half reactions are compared to H2
Ag+ reacts with H2 spontaneously            Eo = +0.80 v




Zn2+ is nonspontaneous with H2              Eo = -0.76 v

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
HNO3 is both
H+ and NO3-
Take higher one
Stronger Oxidizing
Agent
             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 v
SO42-                    reducing
                                      Oxidation

The reaction is reversed so the E0 = -2.01 v
             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
SO42-                    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
SO42-                   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 v
SO42-                   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
  The top reaction is written forward
   Reduction



                                                            Oxidation


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
                          simplify                add potentials

      2(MnO4- + 8H+ + 5e-→ Mn2+      + 4H2O)               1.51 v

      5(Mn2+ + 2H2O → MnO2(s)+ 4H+ + 2e-)         -1.22 v
            3      2                          4
2MnO4-+16H++5Mn2++10H2O → 2Mn2++8H2O+5MnO2(s)+20H+ 0.29 v

2MnO4- + 3Mn2+ + 2H2O →      5MnO2(s) + 4H+               0.29 v
                                 positive voltage- spontaneous