# Potential of hydrogen electrode

1. Jul 4, 2016

### TT0

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
From the calculation of the potential of the cell and the potential for the copper electrode, it states that the hydrogen electrode has a potential of -0.09 V. But I thought hydrogen electrode is standard so it should be zero. Therefore I am not sure between C and D. Can someone explain which one is right and why?

Cheers!

2. Jul 4, 2016

### Staff: Mentor

What does it mean "standard electrode"? What does it mean "standard potential"?

3. Jul 4, 2016

### TT0

Standard electrode is a standard hydrogen electrode. Standard potential is the difference in voltage between the standard hydrogen electrode and the concerning electrode. I guess the hydrogen electrode could be non standard as you don't know it's solution's molarity and what M is. This means the answer is D?

Cheers!

4. Jul 4, 2016

### Staff: Mentor

"Standard is a standard" is a tautology and it doesn't add much to the problem.

What is the definition of the standard potential?

Actually it seems like you are aware of what is important here, but you failed to mention it correctly.

5. Jul 4, 2016

### TT0

I am not too sure. I think standard potential is the reducing strengths of the other electrodes relative to the standard hydrogen electrode.

6. Jul 4, 2016

7. Jul 5, 2016

### TT0

Standard potential is the measure of the energy per unit charge which is available from the oxidation/reduction reactions of each electrode relative to the standard hydrogen electrode. So as the hydrogen electrode is not the standard one, it's reduction potential can be non-zero so D is the answer?

Cheers!

8. Jul 5, 2016

### Staff: Mentor

Sadly, this definition doesn't touch on a very important point - standard potential requires the system to be in the standard state.

9. Jul 6, 2016

### TT0

I see, thanks!