how do i calculate a concentration ratio of oxidised to reduced cytochrome c Fe2+ to Fe3+

given at 25 C and pH7
E(mV) as 100
and absorbance at 550nm as 1.5

E is relative to standard hydrogen electrode

i know im supposed ot use the nernst equation i just don't know how im supposed to use this data to something which i can use in the nernst eq

please help

To calculate the concentration ratio of oxidized (Fe3+) to reduced (Fe2+) cytochrome c, you can use the Nernst equation. The Nernst equation relates the standard reduction potential (E°) of a reaction to the concentration of the species involved. In this case, the Nernst equation for the oxidation/reduction of cytochrome c is:

E = E° - (RT/nF) * ln(Q)

Where:
- E is the measured electrode potential (in volts)
- E° is the standard reduction potential (in volts) relative to the standard hydrogen electrode
- R is the gas constant (8.314 J/(mol*K))
- T is the temperature in Kelvin
- n is the number of electrons transferred in the reaction
- F is the Faraday constant (approximately 96,485 C/mol)
- Q is the reaction quotient, which is the ratio of the concentrations of the oxidized and reduced species

To use this equation, you need to know the standard reduction potential (E°) and the ratio of oxidized to reduced species (Q). The E° for the cytochrome c Fe3+/Fe2+ couple is usually around 100 mV at pH 7 and 25°C, so you can use this value.

To determine Q, you need to know the concentration of either the oxidized or reduced form of cytochrome c. In this case, we don't have direct concentrations, but we have the absorbance at 550nm.

To convert absorbance to concentration, you need to establish a calibration curve first. You can measure the absorbance of known concentrations of cytochrome c Fe3+ or Fe2+ and plot a graph relating absorbance to concentration. From this calibration curve, you can then determine the concentration of the species based on the given absorbance of 1.5 at 550nm.

Once you have the concentration of either the oxidized or reduced cytochrome c, you can substitute it into the Nernst equation to calculate the concentration ratio of oxidized to reduced cytochrome c.