Cell Notation - Video Tutorials & Practice Problems
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1
concept
The Cell Notation
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Now you're going to say that our cell rotation also called our cell diagram is a quicker method to describe the overall redox reaction in an electrochemical cell. Now, here we're gonna have two types of boundaries involved. We have our phase boundaries and then we have our physical boundaries. Our phase boundaries represents a solid line going up here. We're gonna say this is the condition where two phases of the same substance can coexist at equilibrium. Our physical boundary is shown as two solid lines going up. This is the physical space that separates the A node and the cathode of your electrochemical cell. So when we're talking about a cell notation or cell diagram, we're referring to this portion here. Now, within this cell diagram or cell notation, we can plug in different um elements, different types of ions, different types of compounds. So how exactly do we do that? Well, here, let's take a look at our electrochemical cell in this electrochemical cell, we have the A node on the left and we have the cathode on the right here. We're going to assume that we're dealing with a spontaneous electrochemical cell, otherwise known as the galvanic or voltaic cell. That means that our a node would be negatively charged and our cathode positive. Remember the anote is the site of oxidation and the cathode is a site of reduction. Remember, oxidation, we're losing electrons. So electrons will be leaving here. We have a chromium electrode. It'd be leaving and heading towards the calf though the volt meter would just register the amount of electricity being generated by the transferring of electrons from the a node to the cathode. Here, we know that the copper electrode is gaining these electrons. Now, if we think about this reaction in terms of half reactions, we're gonna say here canceling out the intermediates gives the overall reaction. Now in the catholic compartment, what's going on? We know reduction is occurring if reduction is recurring, the electron is reacted. So if we look at the catholic compartment, we have cu two plus ions and the copper neutral form. So here we have cu two plus, it will gain two electrons and that will create rcu neutral form the atom compartment where oxidation is occurring with oxidation. Remember electrons are products. We have the chromium electrode and the cr two plus ions within the solution. So here we'd have our cr solid. This is solid here and this is aqueous here. So we have cr solid being oxidized to give us cr two plus aqueous. And here go the two electrons we're producing over here are intermediates. Your electrons must always be intermediates and they have to be the same number two electrons, two electrons, they cancel out what's left at the end is our overall redox reaction. So that give us cu two plus aqueous plus chromium solid gives us cu solid plus cr two plus aqueous. We have our half reactions, we cancel out the intermediates. Then we have our overall reaction. Now we go to the cell notation portion. Remember the cell notation portion is a quicker way of drawing or describing what's happening here in the electrochemical cell. You don't have time to draw this for another chemist. So you quickly write it down in cell notation form. Now, memory tool here, cell notation is as easy as ABC. That's because we have a phase boundary here which is a, we have our physical boundary which is B and here we have our next phase boundary which is C A is for Anade. So this portion here represents the adult compartment B is the physical break. So the physical space between my two half cell containers and then C you probably guessed it is the cat though. So this portion represents the cathode. Now, when it comes to this cell notation, we'd say that the lower oxidation states or lower oxidation numbers will be found on the ends on both sides. And then the higher oxidation numbers would be found inside. With this information, we can write our cell notation here based on what's going on in this electrochemical cell. So on the animal compartment, we have chromium neutral and chromium two plus chromium neutral has an oxidation number zero problem. Two plus has an oxidation number of two plus. So the lower oxidation numbers on the end. So C are solid, higher oxidation number in the in the center co2 plus C food compartment over here. What are the two species interacting with each other? That are the same substance? We have copper two plus ion and and just copper neutral, their higher oxidation state is copper two plus which would be in the interior and then copper solid here on the end. So basically, this cell notation or cell diagram is equivalent to me drawing this entire electrochemical cell at least in its basic design. Well, we're not talking about the ions in the salt bridge we're just talking about OK, we have an adult compartment. These are the species involved. We have our catholic compartment and then these are the species involved and how they interact with each other. So just from this information, we don't need to draw an entire electrochemical cell. So that's the beauty of our C notation or cell diagram.
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example
Cell Notation Example
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1m
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He says consider an electrochemical cell where the f reaction takes place from this overall redox reaction. It asks what is the cell rotation for this cell or remember cell mutation? We're gonna have a phase boundary, a physical boundary and another phase boundary. So notation is is easy as ABC where A represents our A node B is our physical break between both half cell compartments or containers. And C as are Catholic, remember that our lower oxidation numbers are on the ends and then our higher oxidation states or numbers are in the interior or inside. So here if we take a look at our overall reaction, we have 10, 2 going to 10 neutral. Its oxidation number goes from plus two, 20, its oxidation number was reduced. Therefore, it represents the cathode. So here it'd be in the Catholic compartment, which is this portion here. Remember the higher oxidation state is on the interior. So that'd be SN two plus aqueous and then the lower one is on the end. So that'd be s and solid aluminum goes from zero to plus three. Its oxidation number went up. So it's been oxidized and therefore represents the Anno again, the higher oxidation states on the interior. So A L three plus aqueous and the lower oxidation state is on the end A L salt. So this here would represent our cell notation or cell diagram for the following electrochemical cell.
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Problem
Problem
Write the half reactions as well as the overall net ionic equation for the following line notation:
Fe (s) | Fe2+ (aq) || H+ (aq) | H2 (g) | Pt (s)
A
Fe (s) + 2 H+ (aq) → Fe2+ (aq) + H2 (g)
B
Fe2+ (aq) + H2 (g) → Fe (s) + 2 H+ (aq)
C
Fe2+ (aq) → Fe (s)
D
H2 (g) → 2H+ (aq)
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Problem
Problem
The cell notation for a redox reaction is given as the following at (T= 298 K). Calculate the cell potential for the reaction at 25ºC.
Zn (s) | Zn2+ (aq, 0.37 M) || Ni2+ (aq, 0.059 M) | Ni (s)
Standard Reduction Potentials
Zn2+ (aq) + 2 e– →. Zn (s) E°red = - 0.7621
Ni2+ (aq) + 2 e– → Ni (s) E°red = - 0.2300
A
0.3130 V
B
0.4033 V
C
0.5085 V
D
0.1199 V
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Problem
Problem
What is the [Cu2+] for the following cell notation diagram if the cell potential is 0.4404 V?
