Finding ΔG and K for a given redox reaction

[anisotropic]

Homework Statement

Redox reaction:
B-hydroxybutarate + 1/2O₂ -> acetoacetate + H₂O

Half reaction 1:
O₂ + 4H⁺ + 4e^- -> 2H₂O (E = +0.816 V)

Half reaction 2:
acetoacetate + 2H⁺ + 2e^- -> B-hydroxybutarate (E = -0.346 V)

Using standard reduction potentials given,

• calculate ΔG
• calculate the equilibrium constant, K

Conditions are the biochemist's standard state, pH 7, 298.15 K.

Homework Equations

ΔG = -nFΔE

ln K = nFE/RT

The Attempt at a Solution

ΔE_rxn = (0.816 V) + (0.346 V)
ΔE_rxn = 1.162 V

ΔG = -nFΔE
ΔG = -n(96485 C/mol)(1.162 V)

n = ? (moles of electrons transferred)

By writing out both half reactions, the electrons cancel out. Should there not be electrons left over on one side of the equation in order to determine the value of n?

 

[Borek]

No, if electrons are left, reaction is not balanced.

 

[anisotropic]

So 2 mol of e^- per mol of product (n = 2)?

 

[anisotropic]

So 2 mol of e^- per mol of product (n = 2)?

Can someone please confirm this?