I\'m getting prepared for my seminar presentation and am confused on some of the

Question

I'm getting prepared for my seminar presentation and am confused on some of the electrochemisry aspects.

So when i'm splitting water into hydrogen and oxygen. Water --> oxygen & what not is oxidation, while water --> hydrogen is reduction.

The standard cell potential is thus E(reduction) - E(oxidation) = 0.00V - 1.23V = -1.23V.

The part I am not understanding is what does this mean? What does the negative sign mean? What does it tell us about this reaction?

To give some background, I am doing solar water splitting, and from 1.23V I understand the thermodynamic challenges because it is a non-spontaneous reaction; and the kinetic challenges that it needs an activation energy of 1.23V in ideal conditions; but going into the topic of overvoltage: it needs an even higher activation energy under real conditions. Knowing this, I just don't understand how to talk about the standard cell potential.

Explanation / Answer

Solution:

Firstly let be clear with oxidation (loss of electron), reduction(gain of electron),

so you received -1.23 V means its an good oxidizer and the power generation from it will be stable, simply receiving energy on splitting water molecules.

Secondly you have mentioned solar water splitting, in this +1.23 V shows the reduction process (gain of electron) which receives those electrons from sunlight to get reduced, based water quality the activation energy changes.

for example if the water is having zero ppm of particulate then the reduction takes place much quicker and viceversa for hard waters.

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