Chemists: How Do I Calculate Half Wave Potential

I am extremely frustrated. I am doing a lab report on electrochemistry and I cannot for the life of me figure out how to use E(1/2) to identify substances. How do I know what potential some reaction should appear at? For example, I know the "standard potential" of O2(g) + 4H+ + 4e- <=>2H2O = +1.229 V. This same textbook that gives me this information has a diagram where this reaction has an E(1/2) of ~-0.9 or -1 V vs SCE. Do I subtract 2.2 for the SCE to get the E^o=1.229? If so, how come this doesn't work for the peak they show at ~-0.1 for the reduction of O2 to H2O2? (-0.1 - 0.22 ~ -0.3 =/= - 0.68 = - E^o).

Originally posted by AThousandYoung
I am extremely frustrated. I am doing a lab report on electrochemistry and I cannot for the life of me figure out how to use E(1/2) to identify substances. How do I know what potential some reaction should appear at? For example, I know the "standard potential" of O2(g) + 4H+ + 4e- <=>2H2O = +1.229 V. This same textbook that gives me this informa ...[text shortened]... eak they show at ~-0.1 for the reduction of O2 to H2O2? (-0.1 - 0.22 ~ -0.3 =/= - 0.68 = - E^o).

STFU or I will smite thee. 😉

I found out. Apparently it's standard potential minus electrode potential. I was using the wrong reaction apparently.

THANKS FOR NOTHING RHP!!!1!

Originally posted by AThousandYoung
STFU or I will smite thee. 😉

I found out. Apparently it's standard potential minus electrode potential. I was using the wrong reaction apparently.

THANKS FOR NOTHING RHP!!!1!