Question

Corrosion is the electrolytic oxidation of metals by air. The half equations for the rusting of iron are:

1/2 O2 (g) + H2O (l) + 2e^- ---> 2OH^- (aq) E^o = +0.40 V

Fe^2+ (aq) + 2e^- ---> Fe (s) E^o = -0.44 V

1. Write the overall equation for the rusting process and calculate the EMF of this reaction under standard conditions.

2. Standard conditions are not what is normally found in the environment. In the natural environment the pressure of O2 (g) is approximatley 0.2 atm, pH of rain water is approximatley 5 and this modifies the Ecell for the O2, H2O/OH system to +0.66 V. How will this affect the rusting process.