[VISUAL] In human cells a compound known as NADH is involved in a reaction that generates an electri — Electrochemistry Chemistry Question
Problem Context
[VISUAL]
In human cells a compound known as NADH is involved in a reaction that generates an electrical potential. The reaction is based on the two half-reactions shown in the table above. The balanced equation for the overall reaction is shown below.
O2 + 2 H+ + 2 NADH → 2 H2O + 2 NAD+
Model Answer
Four moles of electrons are needed to convert the two moles of O atoms in one mole of O2 from the zero oxidation state to the −2 oxidation state.
1 point is earned for the correct answer.
Model Answer
E°cell = +0.815 V ‒ (‒0.320 V) = +1.135 V
1 point is earned for the correct answer.
Model Answer
Yes, the reaction is thermodynamically favorable because the standard cell potential, E°cell, is positive (E°cell = +1.135 V), which means the standard Gibbs free energy change, ΔG°, is negative (ΔG° = −nFE° < 0).
1 point is earned for the correct answer with a valid justification.
Model Answer
Increase. The highly negative ΔG° indicates that the value of K for this reaction is very large, so decreasing Q causes the system to deviate further from equilibrium, thus increasing the magnitude of the electrochemical potential. 1 point is earned for the correct answer with a valid justification.