[antoinetta]

I'm having trouble with setting the equation for this question:

What is the maximum useful  work which can be obtained from a hydrogen-oxygen fuel cell that produces 1.36 kg of water at 25°C?  (Assume 1 atm pressure for the gases.)

So, I changed the mass of water to moles which is 75.56 g/mol

Work = -nFE⁰
F = 96487 J/V mole e^-

So, I know this:  O_2(g) + 4H⁺(aq) + 4e^- -> 2H₂O E⁰(V) = 1.23V

Where do I go from here?

[Yggdrasil]

(Delta)G tells you the maximum amount of non-PV work that can be extracted from the system.  Use the equation (Delta)G = -nFE⁰ to find (Delta)G.