Chemistry electrode help pls

4

I’ve come across a question saying:

Write the conventional representation for the cell used to measure the standard electrode potential for the conversion of tin2+ ions to tin

The standard electrode potential for the equation forming Sn(s) from Sn2+ (+2e-) is -0.14

The answer says:

Pt|H2|H+||Sn2+|Sn

I’m confused why:
1. The hydrogen potential is on the left when its electrode potential is more positive than the Sn equation.
2. Why the aqueous H plus is next to the salt Bridge and the gaseous H2 is to the left when the gaseous substances are usually next to the salt bridge

Reply 1

Nitrotoluene

12

Original post

by Spottedcat9274

I’ve come across a question saying:
Write the conventional representation for the cell used to measure the standard electrode potential for the conversion of tin2+ ions to tin
The standard electrode potential for the equation forming Sn(s) from Sn2+ (+2e-) is -0.14
The answer says:
Pt|H2|H+||Sn2+|Sn
I’m confused why:
1. The hydrogen potential is on the left when its electrode potential is more positive than the Sn equation.
2. Why the aqueous H plus is next to the salt Bridge and the gaseous H2 is to the left when the gaseous substances are usually next to the salt bridge

It's so true that getting your hands dirty with the material is the best way to learn.
First things first, what exactly is a standard electrode potential? Well, it's always measured by comparing it to a go-to reference point, the standard hydrogen electrode (SHE). This SHE has a standard potential that we've all agreed on.
Now, picture an electrochemical cell, it's like having two separate zones, or "half-cells." In one area, oxidation is taking place, while in another, reduction is happening. The electrode where oxidation kicks off is the anode, and the one where reduction takes place is the cathode.
Think of the left side as the place where the oxidation half-cell (that's the anode) lives.
The right side is where you'll always find the reduction half-cell (the cathode).
A single vertical line (|) means, " We're moving from one phase to another," from a solid to a liquid. Double vertical lines (||), on the other hand, tell us, "This is where the salt bridge is – it lets ions move between the two zones."
Within each of these half-cell descriptions, we usually put the actual electrode material on the very outside and the ions that are in the solution closer to that salt bridge. Oh, and we often pop in little notes in parentheses to say whether something is a solid (s), liquid (l), gas (g), or dissolved in water (aq).
Now, let's tackle those specific points you raised:
So, why is the hydrogen potential hanging out on the left side? It's all about how we measure standard potential. We always compare it to the SHE. In your particular setup, for the whole cell reaction to work the way it does, the SHE has to undergo oxidation. And remember, the left side of our cell diagram is where we show oxidation happening.
And what's the deal with the aqueous H^+ being next to the salt bridge and the gaseous H2 being more to the left? Well, think about what the salt bridge does, it's the connection point between the two solutions in our half-cells. So, it makes sense that the stuff dissolved in water (H^+)(aq) in the hydrogen half-cell would be right next to that bridge. As for the hydrogen gas (H2(g)), in a standard hydrogen electrode, we bubble this gas over a platinum (Pt) electrode (which doesn't react, it just provides a surface). Following these little rule of putting the electrode material on the outer edge of the half-cell description, the Pt and the H2(g) end up on the left of the H^+ (aq).
Working through these little details should hopefully make things much clearer for you.
Here is my 2 cents!

(edited 10 months ago)

Reply 2

Spottedcat9274

OP

4

Original post

by Nitrotoluene

It's so true that getting your hands dirty with the material is the best way to learn.
First things first, what exactly is a standard electrode potential? Well, it's always measured by comparing it to a go-to reference point, the standard hydrogen electrode (SHE). This SHE has a standard potential that we've all agreed on.
Now, picture an electrochemical cell, it's like having two separate zones, or "half-cells." In one area, oxidation is taking place, while in another, reduction is happening. The electrode where oxidation kicks off is the anode, and the one where reduction takes place is the cathode.
Think of the left side as the place where the oxidation half-cell (that's the anode) lives.
The right side is where you'll always find the reduction half-cell (the cathode).
A single vertical line (|) means, " We're moving from one phase to another," from a solid to a liquid. Double vertical lines (||), on the other hand, tell us, "This is where the salt bridge is – it lets ions move between the two zones."
Within each of these half-cell descriptions, we usually put the actual electrode material on the very outside and the ions that are in the solution closer to that salt bridge. Oh, and we often pop in little notes in parentheses to say whether something is a solid (s), liquid (l), gas (g), or dissolved in water (aq).
Now, let's tackle those specific points you raised:
So, why is the hydrogen potential hanging out on the left side? It's all about how we measure standard potential. We always compare it to the SHE. In your particular setup, for the whole cell reaction to work the way it does, the SHE has to undergo oxidation. And remember, the left side of our cell diagram is where we show oxidation happening.
And what's the deal with the aqueous H^+ being next to the salt bridge and the gaseous H2 being more to the left? Well, think about what the salt bridge does, it's the connection point between the two solutions in our half-cells. So, it makes sense that the stuff dissolved in water (H^+)(aq) in the hydrogen half-cell would be right next to that bridge. As for the hydrogen gas (H2(g)), in a standard hydrogen electrode, we bubble this gas over a platinum (Pt) electrode (which doesn't react, it just provides a surface). Following these little rule of putting the electrode material on the outer edge of the half-cell description, the Pt and the H2(g) end up on the left of the H^+ (aq).
Working through these little details should hopefully make things much clearer for you.
Here is my 2 cents!

Thank you!

Chemistry electrode help pls

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