Half-Cell Potential: Understand What It Means & Why It Matters

[Itskitty]

Half-cell potential?

According to an online chemistry website ( www.chem1.com)
If the half-cell potential for Zn/Zn+ electrode is defined as the potential difference between a piece of metallic zinc and the solution when the reaction Zn2+ + 2e- -> Zn (s) takes place.

That is E cell = V metal - V solution

What does this means?

Is the metal referring to the electrode and the solution referring to the Zn2+?

If it is so, then why do half cells with higher potential difference undergo reduction more readily than half cells with lower potential difference?

I mean the potential difference is supposed to be associated with positive charges, right?

So if one thing has higher potential, then positive charges would want to move to another thing with fewer amount of positive charges.

That, in reality, means that the e- would flow from Ag+ to Ag.

Which is not the usual case?

Could anyone help me with this?

I understand that in the activity series,
we're comparing the performance of each species to those of Hydrogen, so
the higher the potential, the better electron acceptor it will be.

But what about this potential thingy??

Thanks!

 

[pzona]

Yes, the solid is the electrode and the Zn2+ is the solution. The reaction you wrote out is a reduction half reaction, and so you would be looking at the reduction potential. This will be positive because the standard hydrogen cell is defined as the zero for these numbers. Basically it's only positive in relation to the SHE, but then again, I'm not exactly sure if this is what you were asking.

Also be careful with using the word charge. We're dealing with oxidation numbers here, not formal charge.

 

[Itskitty]

Thank you for your reply. :D

That's not my question tho
but i'll think abt it more and post some more questions
may be I'm confusing myself :(

 

[pzona]

Let's break this down; how familiar are you with redox reactions? Are you just starting to learn about them? It seems like you're not looking at the cell as a whole, which consists of an oxidation AND a reduction. The direction in which each half reaction proceeds is relative to the potential

Does your question come from a specific example? If so, it would probably help to post all the information you're looking at, and which parts you don't understand.

 

[LudusRex]

I can explain the concept of half-cell potential and its significance in electrochemistry.

Firstly, a half-cell is a system consisting of a metal electrode and a solution containing ions of the same metal. The half-cell potential is the measure of the tendency of the metal to lose or gain electrons in the solution. In simpler terms, it is the measure of the ability of the metal to undergo oxidation or reduction.

In the given example, the half-cell potential for the Zn/Zn+ electrode is the potential difference between a piece of metallic zinc and a solution containing zinc ions. This potential difference is measured in volts (V) and is denoted as Ecell.

The equation Ecell = Vmetal - Vsolution represents the difference in potential between the metal (electrode) and the solution. The metal here refers to the electrode, while the solution refers to the Zn2+ ions in the solution.

Now, a higher half-cell potential indicates a greater tendency for the metal to undergo reduction (gain electrons), while a lower potential indicates a greater tendency for the metal to undergo oxidation (lose electrons). This is because the potential difference is associated with the movement of positive charges. A higher potential difference means that there is a greater driving force for the movement of electrons from the metal (higher potential) to the solution (lower potential).

In the case of the Zn/Zn+ electrode, the electrons will flow from the metal zinc (higher potential) to the solution containing Zn2+ ions (lower potential), leading to the reduction of Zn2+ ions to Zn metal. This is the usual case in electrochemical reactions.

However, in the activity series, we are comparing the performance of different metals to that of hydrogen. The higher the potential of a metal, the better it will be at accepting electrons and undergoing reduction. This is because hydrogen has a standard half-cell potential of 0 V, and any metal with a higher potential will have a greater driving force for the reduction reaction.

In conclusion, the half-cell potential is an important concept in electrochemistry as it helps us understand the tendency of metals to undergo oxidation or reduction in a solution. It also plays a crucial role in predicting the direction of electron flow in a redox reaction.