[oyvind23]

Hi, I have two questions that I am not so sure about.

1) Find E^o and Q for the reaction H⁺ + e^- -> ¹/₂H₂ at pH=4.

E^o can just be found in SI Data, but I am not sure if I have found Q the right way.

[itex]Q=\frac{P(H_2)^{\frac{1}{2}}}{[H^+]}[/itex] . I just think that P(H₂)=1 atm because that's the pressure in the atmosphere, but I have not taken the hydrostatical pressure and so on. I just don't see how I can calculate it. Are there any formulas to calculate Q from E^o? [H⁺]=10^-pH, so that's not any problem. Eventually, how do I calculate Q?

2) Given the two half-reactions:
O₂ + 4 H⁺ + 4 e^– -> 2 H₂O
O₂ + 2 H₂O + 4 e^– -> 4 OH^–.
How can we get E=0?


I just thought that we could wait until it reaches equilibrium, because at equilibrium E=0. Or just add acid or base to make it reach equilibrium faster. Are there any other possibilities?

Thanks!