Cell Potential: Standard - Video Tutorials & Practice Problems
Get help from an AI Tutor
Ask a question to get started.
1
concept
Standard Cell Potential Calculations
Video duration:
1m
Play a video:
Here we're going to say that our standard cell potential is represented by the variable e naught cell. Here it is the measure of the reduction potential or standard reduction potential, so E not red, in volts between two half cells, so our cathode compartment and our anode compartment. Here, remember, standard refers to the ions within the half cells having values of 1 molar, 1 atmosphere and a pH equal to 7. Volts is represented by capital V. It represents the amount of work done as the electron travels from one electrode to another. Here, volts is also units equal to units of joules per coulomb. Coulomb is a variable we've seen in earlier chapters. Coulombs uses the variable capital C, and it's just the SI unit for electric charge. Now here we're going to say that our standard cell potential of an electrochemical cell is calculated by the formula that it equals cathode minus anode. So remember, an electrochemical cell is composed of 2 half cells, one being the cathode, one being the anode. If you can successfully determine which one is the cathode and which one is the anode, simply use this, formula here, and you'll be able to find your standard cell potential.
2
example
Standard Cell Potential Example
Video duration:
1m
Play a video:
Here it says, what is the standard cell potential for a voltaic cell based on the following reduction reactions in which the copper electrode is the cathode and the zinc electrode is the anode. Alright. So here we have 2 half reactions. In the first one, we have zinc ion absorbing 2 electrons and becoming zinc solid. It has a standard reduction potential of negative 0.7621. Here the units will be in volts. Then we have our copper reduction reaction where a copper 2+ion accepts 2 electrons to become copper solid. It has a standard reduction potential of 0.3394 volts. Now within the question, I tell us that the copper electrode is the cathode and the zinc electrode is the anode. From this point, we just remember that our standard cell potential, so E naught cell equals cathode minus anode. So plug them in, so 0.3394 volts minus a minus point 7621 volts. Remember, a minus of a minus really means they're adding, so add them together. When we do that, we get our final answer as 1.1015 volts as the voltage of our standard cell potential for this particular question. Right? So again, 1.1015 volts would be our final answer.
3
concept
Galvanic Cell and Standard Cell Potential
Video duration:
1m
Play a video:
Now recall that a standard sub potential value that's greater than 0 means the reaction is spontaneous, and when it comes to electrochemical cells, remember we have 2 types. We have our galvanic voltaic cell. Remember, galvanic voltaic, they're synonymous with each other. You can use them interchangeably. And then we have our electrolytic cell. These are our 2 typical types of electrochemical cells. Now for galvanic voltaic cell, we're going to say that the cathode is the half cell compartment that has the higher standard reduction potential, and then the anode is the one that has the lower standard reduction potential. This results in a standard cell potential that is greater than 0. So this makes sense here because a galvanic orbital cell is a spontaneous electrochemical cell, so we'd expect it to have a cell potential greater than 0. The electrolytic cell, on the other hand, everything is kind of reversed here. Here, the cathode is now the one with the lower standard reduction potential, and then the anode is the one with the higher standard reduction potential. Remember, your standard cell potential is still cathode minus anode. Because of this, the standard cell potential here will be less than 0. Alright? So just remember, if we know the type of electrochemical cell, that kind of guides us into what our standard cell potential should be at the end. And that's based on, should the cathode have a higher or lower standard reduction potential, or should it be the anode? Knowing this is key to getting the right answer at the end, so keep this in mind when looking at the 2 types of electrochemical cells.
4
example
Standard Cell Potential Example
Video duration:
2m
Play a video:
Here it says, given the final redox reaction, we have cerium solid plus aluminum ion reacting to produce aluminum solid plus cerium aqueous. Here it says, find its standard cell potential when given the following half reactions. Here we're given the half reaction for the cerium 3+ion and the aluminum ion. Now here the steps that we take is first refer to the redox reaction to determine which species is reduced and which is oxidized. This is incredibly important because remember that the cathode is a site of reduction, so the cathode equals reduction and the anode is the site of oxidation, so the anode equals oxidation. Once we know this, we can use the standard cell potential formula to find our fine length, and that's because standard cell potential, so e naught cell equals cathode minus anode. If we take a look here, we see that cerium solid goes from 0 for its oxidation state, 2 plus 3. If oxidation number increased, therefore, it has been oxidized. So here, if it's the site of oxidation, that means it must be the anode. And then if we look at aluminum, aluminum goes from what? It goes from plus 3 in terms of its charge slash oxidation state to neutral, to its natural standard state, which is 0. So it goes from plus 3 to 0. Its oxidation number has been reduced or decreased, so reduction has occurred, therefore it is the cathode. So we've determined the cathode and the anode, and now we can find the standard cell potential. So take the values and plug them in. So for this will be negative 1.6 77 minuteus a minus 2.336. Remember, a minus of a minus just means that you're adding them together. So negative 1.677 plus 2.336 gives me at the end 0 point 659 volts. This will represent the answer for my standard cell potential for the following example question.
5
Problem
Problem
Calculate the standard cell potential of an electrolytic cell when given the following half reactions.
Standard Reduction Potentials
Fe3+(aq) + e – → Fe2+ (aq) E°red = + 0.769 V
Li+ (aq) + e – → Li (s) E°red = – 3.04 V
A
–2.271 V
B
–1.551 V
C
–3.060 V
D
–3.809 V
6
Problem
Problem
Use the standard half-cell potentials listed below to calculate the standard cell potential for the following reaction occurring in an electrochemical cell at 25°C.