Conventional Cell Representation Alkaline Hydrogen-Oxygen Fuel Cell Help

The question asked to write the 'Conventional Cell Representation Alkaline Hydrogen-Oxygen Fuel Cell'
the mark scheme says this Pt|H2(g)|OH–(aq),H2O(l)||O2(g) |H2O(l),OH–(aq)|Pt it also says 'the h2o is not essential' so Pt|H2(g)|OH–(aq)||O2(g) |OH–(aq)|Pt
My question is why is the OH- closest to the phase boundary as the most oxidized species should be there ie H2?

Can I see the question?

It's not the most oxidized species. It's the species formed in the solution which is in contact with the electrode which is next to the double lines. The question states that "commercial cells use porous platinum electrodes in contact with concentrated aqueous potassium hydroxide." So the species is OH^- . Not H⁺ or H₂. It also states that it's an alkaline cell not an acidic cell. If it was an acidic cell then it would be H⁺.

The question asked to write the 'Conventional Cell Representation Alkaline Hydrogen-Oxygen Fuel Cell'
the mark scheme says this Pt|H2(g)|OH–(aq),H2O(l)||O2(g) |H2O(l),OH–(aq)|Pt it also says 'the h2o is not essential' so Pt|H2(g)|OH–(aq)||O2(g) |OH–(aq)|Pt
My question is why is the OH- closest to the phase boundary as the most oxidized species should be there ie H2?

The Hydrogen atom in the LHS OH- ion has an ox. state of 1.The Hydrogen atom in the LHS H2 molecule has an ox. state of 0. Because the H in the OH- has a higher ox. state, its written closer to the salt bridge. Hope this helps.

Hi Sniperdon227

I remember this question and the mark scheme is awful! I have actually queried this question with the exam board and forced a response. The answer I would give to this question is this:

Pt I H2 I H2O II O2 I OH- I Pt

The reason for this is because from the equations given H2 is oxidised to H2O (zero to +1) and then in the next equation O2 is reduced to OH- (zero to -2).

I hope that helps a bit, and as I have already said, the answer I have given would gain the marks, confirmed by AQA.

Thanks

Alex