Cell Diagram and Ecell [ENDORSED]

[Tarika Gujral 1K]

1) With gaseous and nonconducting solid compounds, is the order
Inert|Gas/solid|Chg || Chg|Gas/solid|Inert?
Or does it follow the order of reactants to products?
Inert|Ox Reactant|Ox Product || Red Reactant|Red Product|Inert

2) With a positive Ecell, reduction is always on the right. Is this order reversed when Ecell < 0?

[Jesse Kuehn 1B]

I believe the solid is always on the outside (or just inside the inert part) so the second form should always be right, and yes everything is reversed when the E is less than zero.

[Chem_Mod]

Using what I discussed in class, and the example I did in class:

ANODE (LEFT) || CATHODE (RIGHT)

Cu(s) | Cu²⁺(aq) || Fe³⁺(aq), Fe²⁺(aq) | Pt(s)

Put the conducting solids (electrodes) on the outside and aqueous next to the salt bridge.

Always include phase in the equation and cell diagram.

In a homework problem, there is a cell diagram answer key written as: Pt(s) | I- (aq) | I₂(s) || .......

This is a saturated I-(aq) solution with undissolved I₂(s) in the same solution. Both the salt bridge and the platinum electrode are in contact with the same saturated I-(aq) solution.
As one can see this simple notation does give the information needed to build or visualize the cell (battery).

Another homework problem used KOH (aq) instead of OH- (aq), but you do not need to include K if there is no information about potassium in the question. You can just put OH-(aq) to indicate alkaline conditions.

In cell diagrams: Anode (oxidation half-reaction) is always on the left; and the cathode (reduction half-reaction) is always on the right.

Some homework problems intentionally ask what is wrong with a given cell diagram, and an incorrect notation is given (which one can figure out because the voltage is negative).
By switching the left and right half-reactions one gets the correct cell diagram with a positive voltage.
To be correct the cell (battery) must have a positive voltage (as I repeated and joked about in class :-).

[jane_ni_2d]

how can you tell which is the anode and which is the cathode?

[davidryan3f]

how can you tell which is the anode and which is the cathode?

the anode is always on the right of the cell diagram and the cathode is on the right.

[riddhiduggal]

In which cases do you flip the sign for the E, when calculating Ecell?

[lukezhang2C]

For a Galvanic Cell it should be Anode || Cathode, where there are single lines (|) separating different states of matter, and commas separating different agents with the same state of matter. i.e (aq), (aq), || (aq)| (s)

[AnayaArnold_3L]

Thanks for clarifying!!

For a Galvanic Cell it should be Anode || Cathode, where there are single lines (|) separating different states of matter, and commas separating different agents with the same state of matter. i.e (aq), (aq), || (aq)| (s)

[bloodorangefield]

How do you tell the difference between when it is an anode vs when it is cathode?

[Caroline Beecher 2H]

How do you tell the difference between when it is an anode vs when it is cathode?

An anode represents the oxidation half-reaction and a cathode represents the reduction half-reaction. The anode is usually on the left and the cathode is on the right.

[Julia Holsinger_1A]

How do you tell the difference between when it is an anode vs when it is cathode?

anode is always on the left and cathode is on the right

[805421690]

how can you tell which is the anode and which is the cathode?

the anode is always on the right of the cell diagram and the cathode is on the right.

I thought the anode is always on the left of the cell?

[Phoebe Joseph]

how can you tell which is the anode and which is the cathode?

the anode is always on the right of the cell diagram and the cathode is on the right.

Do you mean the anode is always on the left?

[Phoebe Joseph]

Also, the solid that the reaction is taking place on are always at the very edges of the diagram, correct? (except liquid mercury that is an exceptional liquid conductor)

[DavidTabib 3H]

Solids are always on the outside of the cell diagram and everything is reversed when E is less than 0.

[Alexis Sanft 1E]

Is water the only thing not included?

[Phoebe Joseph]

Is water the only thing not included?

Yes, water is the only thing not included because it is the solvent.

[Vanessa Wiratmo 3k]

anodes are on the left and cathodes are on the right when using this notation
(II) signifies the salt bridge
(I) signifies phases change in contact with one another
(,) signifies same phase in contact with one another

Solids are written on the outside of the reaction

[405825570]

How do you know when to add Pt, and which side does it go on? thanks

[405825570]

Also, with cell diagram notation, does the anode always have to be on the left and the cathode on the right? thanks

[Diego Salgues 2K]

Anodes are on the left and cathodes are on the solid. Make sure there is a solid on each side as well.

[Ella Figueroa 2H]

Is water the only thing not included?

Yes, water is the solvent and therefore is not included. Though water is not the only solvent possible, solvents can also include ethanol, methanol, and acetone. Whatever the solvent is, it will not be included within the calculations.

[905771517]

galvanic cells are usually written on the left side of the double vertical line and the cathode (where reduction occurs) is written on the right side. Therefore, the general convention for the order of species in the Nernst equation for a galvanic cell is:

anode (oxidation) | cation || anion | cathode (reduction)

[Emily Vargas 2I]

Using what I discussed in class, and the example I did in class:

ANODE (LEFT) || CATHODE (RIGHT)

Cu(s) | Cu²⁺(aq) || Fe³⁺(aq), Fe²⁺(aq) | Pt(s)

Put the conducting solids (electrodes) on the outside and aqueous next to the salt bridge.

Always include phase in the equation and cell diagram.

In a homework problem, there is a cell diagram answer key written as: Pt(s) | I- (aq) | I₂(s) || .......

This is a saturated I-(aq) solution with undissolved I₂(s) in the same solution. Both the salt bridge and the platinum electrode are in contact with the same saturated I-(aq) solution.
As one can see this simple notation does give the information needed to build or visualize the cell (battery).

Another homework problem used KOH (aq) instead of OH- (aq), but you do not need to include K if there is no information about potassium in the question. You can just put OH-(aq) to indicate alkaline conditions.

In cell diagrams: Anode (oxidation half-reaction) is always on the left; and the cathode (reduction half-reaction) is always on the right.

Some homework problems intentionally ask what is wrong with a given cell diagram, and an incorrect notation is given (which one can figure out because the voltage is negative).
By switching the left and right half-reactions one gets the correct cell diagram with a positive voltage.
To be correct the cell (battery) must have a positive voltage (as I repeated and joked about in class :-).

Thank you!! this was really helpful

[Chem_Mod]

Glad my detailed, and time consuming answer, helped. :-)

[Sofi Ghasemzadeh 2G]

The anode is the reducing/negative electrode; this releases electrons, and during a reaction, it oxidizes. On the other hand, the cathode is the oxidizing/positive electrode; this gains electrons, and during a reaction, it experiences reduction. One way to think about it is that cathodes get their name from cations, which are ions that are POSITIVELY charged, whereas anodes get their name from anions, which are ions that are NEGATIVELY charged.

[405718358]

Cathodes have a positive charge while an anode will always have a negative charge. The cathodes are always going to be oxidizing and gaining electrons while the anode is always reducing and releasing the electrons.

[Sydney_Hoang_Dis1B]

how can you tell which is the anode and which is the cathode?

You kind of have to figure out what type of cell it is. A galvanic cell always has a positive potential difference or a positive Eºcell value. This allows us to conclude that the anode is on the left side and the cathode is on the left side.

ANODE || CATHODE when Eºcell is positive
CATHODE || ANODE when Eºcell is negative

For cathodes, the e- tends to be on the reactant side when balancing half reactions.
For anodes, the e- tends to be on the product side when balancing half reactions.
In the end, these e- values will get cancelled out but it is a good thing to know for processes in between for figuring out the final answer. Hope this helps!

[Sydney_Hoang_Dis1B]

In which cases do you flip the sign for the E, when calculating Ecell?

You never flip the sign of the E value. Essentially, Eºcell is reduction potential. You would never have 2 sides of potential, both negative and positive. It's easy to think of it when applying it to other contexts. For example, let's say you have the potential to do something because you are qualified. This potential could never be flipped. This is the way my brain thinks of it but it's kinda strange. All you need to know that Eº values for cathode and anode will never be flipped!

[306060519]

When constructing the order, focus on the solid being the outside of the structure. The other values descend inwards.