Question

The cytochromes are heme‑containing proteins that function as electron carriers in the mitochondria. Calculate the difference in the reduction potential ( Δ E ∘ ′ ) and the change in the standard free energy ( Δ G ∘ ′ ) when the electron flow is from the carrier with the lower reduction potential to the higher. cytochrome c 1 ( Fe 3 + ) + e − − ⇀ ↽ − cytochrome c 1 ( Fe 2 + ) E ∘ ′ = 0.22 V cytochrome c ( Fe 3 + ) + e − − ⇀ ↽ − cytochrome c ( Fe 2 + ) E ∘ ′ = 0.254 V Calculate Δ E ∘ ′ and Δ G ∘ ′ . Δ E ∘ ′ = V Δ G ∘ ′ =

Answer 1

Answer :  The value of $E^o$ and $\Delta G^o$ is, 0.034 V and -3.281 kJ/mol

Explanation :

From the given half reactions we conclude that, the cathode will be with more reduction potential and anode will have low reduction potential.

First we have to calculate the standard electrode potential of the cell.

$E^o=E^o_{cathode}-E^o_{anode}$

$E^o=(0.254V)-(0.220V)=0.034V$

Relationship between standard Gibbs free energy and standard electrode potential follows:

Formula used :

$\Delta G^o=-nFE^o$

where,

$\Delta G^o$ = Gibbs free energy = ?

n = number of electrons = 1

F = Faraday constant = 96500 C/mole

$E^o$ = standard e.m.f of cell = 0.034 V

Now put all the given values in this formula, we get the Gibbs free energy.

$\Delta G^o=-(1\times 96500\times 0.034)$

$\Delta G^o=-3281J/mol=-3.281kJ/mol$

Therefore, the value of $E^o$ and $\Delta G^o$ is, 0.034 V and -3.281 kJ/mol