RESULTS

Table 1 - Potentials of solutions A and B

Solution |
Potential |
Temperature |

A |
343 mV |
22.5 |

B |
261 mV |
22.5 |

Table 2 - The measured potential, Absorbance and transmittance of the three solutions marked 1, 2, and 3.

Test Tube No. |
Absorbance (Average) |
Temperature ( |
Potential (mV) |

1 Reduced |
0.078 |
22.5 |
95.3 |

2 Mixture |
0.061 |
22.5 |
- |

3 Oxidized |
0.030 |
22.5 |
- |

By comparing the potentials obtained from the solutions A and B to the standard values of these solutions the platinum electrode can be calibrated and the potential of the electrode with respect to the Hydrogen electrode is determined. Also, the potential of B should be greater than A as obtained because the ratio of Fe^{III}(CN)_{6}/ Fe^{II}(CN)_{6 }is greater.

CALCULATIONS

- Potential of reference electrode:

E_{o}^{FeIII / FeII Vs Ref} = E_{x}^{measured} - 0.059 log [Fe^{3+}] / [Fe^{2+}]

Solution A E_{o}^{FeIII / FeII Vs Ref} = 0. 343 - 0.059 log ([0.05]/[0.1]) = 325.3 mV

Solution B E_{o}^{FeIII / FeII Vs Ref} = 0. 261 - 0.059 log ([0.05]/[0.01]) = 303.4 mV

Average = 314 mV |

B) Potential of reference electrode relative to hydrogen electrode:

E_{o}^{ Ref Vs H+/H2} = E_{o}^{FeIII / FeII Vs H+/H2} – E_{o}^{FeIII / FeII Vs Ref} = 0.451- 0.314 = 0.137 V

D) Ratio of oxidized to reduced cytochrome c:

__[Oxidized cytochrome c]__ = __( ^{550nm}Absorbance_{reduced cytochrome} - ^{550nm}Absorbance_{redox buffer}) __

[Reduced cytochrome c] (^{550nm}Absorbance_{redox buffer} - ^{550nm}Absorbance_{oxidized cytochrome})

= (0.078 - 0.061)/(0.061- 0.030)

= 0.548

- Electrode potential of protein solution:

E^{observed} = E_{0}^{Ref vs. H+/H2} + E^{measured.redox}

= 0.137V + 0.095V (from above and .0953 from table)

E^{observed} = 0.232V

E_{o}^{cytochrome c }= E^{observed} - (2.3RT/nF) log ( [Oxidized cytochrome c] / [Reduced cytochrome c] )

_{ }= 0.232 V – [(2.3 x 1.987 x 296) / 23,060] log 0.548

= 0.232 V - (-0.0153 V)

E |

- Percent Error:

Actual Redox Potential^{2} = 235 mV

Experimental Redox Potential = 247 mV

% Error = (247 – 235) / 235 = 5.1 %