[Big-Daddy]

What is meant by the sentence: "The standard redox potential of the Fe3+/ Fe2+ system in 1 mol/dm3 HCl is 0.710 V."

I thought the couple Fe³⁺ + e^-  Fe²⁺ would only have one fixed standard redox potential, E°. It might have a different redox potential E, calculated from the Nernst equation, if the reaction it is coupled with is H⁺ + e^-  1/2 H₂, as in this case. But why does it say "standard redox potential" then? And why would this be any different from the normal value of E° for the couple Fe³⁺ + e^-  Fe²⁺ ? (they cannot be the same because in the previous question we were just asked to work out E° for this same couple)