Intro to Electrochemical Cells - Video Tutorials & Practice Problems
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concept
Electrochemical Cells
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Now, an electrochemical cell is just an instrument composed of two half cells connected by a conductive wire. Now here, if we take a look at this image, two half cells, this is a half cell which is in this jar and this is our second house cell, which is our second jar. They're connected via con a conductive wire. Now, within each one of these jars or half cells, we have a metal rod which is our electrode. They're connected together by this conductive wire here where electrons travel. Now here a half cell is a container with a single electrode. So that's that metal rod immersed in an electrolyte solution representing a half reaction. Now, here we go back down here. We can say in this first half cell jar, we have involved M solid electrode and dissolved within the solution are M plus ions. Here, if we take a look at the half reaction, we have m solid giving us M positive plus on an electron when you have an electron as a product that represents an oxidation. And that's because the oxidation number of my rod is increasing, you go from neutral, which is zero oxidation state to here a plus one oxidation state, your oxidation number increased. So that's oxidation. On the other side, we have an X electro rod and dissolved X plus ions. Here, we're going from plus one to neutral. So zero, my oxidation number decreased. So I'm being reduced. So this half cell deals with reduction. So we have one doing oxidation, one doing reduction. So we have in essence is a redox reaction. So we're gonna say through a redox reaction, the transferring of electrons between half cells produces or consumes electricity. Electricity is just the movement of electrons across um conductive wires like we have here in this electrochemical cell. So oxidation is we're losing electrons. So electrons would literally leave this part and travel to the other half cell where reduction occurs. OK. So these are just some fundamental key steps when a within a typical electrochemical cell, we're gonna go into greater detail. But for right now, just remember that an electrochemical cell has two jars to half cells. One is where oxidation occurs and the other is where reduction occurs. The movement of electrons can either produce or consume electricity in this process.
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concept
Cell Potential and Spontaneity
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Here, we're going to say that an electrochemical cell has what we call a cell potential. Now, this cell potential will be under standard conditions or non-standard conditions. Cell potential is E sub cell. If it's under standard conditions, we use not a little circle here or zero. If it's non fat conditions, it doesn't have that little knot or circle. Now, cell potential is just the difference in potential energies as electrons travel between the half cells. Remember one half cell deals with oxidation where we're losing electrons. The other one deals with reduction where we're gaining electrons. The traveling of the electrons is what creates potentially electricity. Now here this will be measured in vaults vaults here will be using the variable V. Now recall standard conditions are 25 °C, one molar, one atmosphere and a ph equal to seven. Under these conditions, we use this cell potential. If we are not following these standard conditions, then we're talking about non-standard cell potential. Now there are two types of electrochemical cells. One that produces electricity, so makes it and one that consumes electricity. So uses it up. These two types of electrochemical cells have names given to them. So one is called a galvanic. This one has a cell potential that is positive, whether that be standard or or non standard, meaning electricity is produced. So if we have an electrochemical cell that is positive in terms of its cell potential, it represents a galvanic cell, galvanic cells produce electricity, an electrolytic cell, my guess is the opposite. It would have a self potential that is negative because of this, it doesn't produce electricity, it consumes or uses it up. So just remember we have standard cell potential and non-standard cell potential. And then we have two types of electrochemical cells based on the idea of either making or producing electricity. So those will be our galvanic cells or consuming or using up electricity. Those would be our electrolytic cells.
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example
Intro to Electrochemical Cells Example
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Which of the following electrochemical cells would use up the largest quantity of electricity at 25 °C. All right. So here they're saying would use up. This means that it's consuming electricity. Here we have electro chemicals, cells A to D each with a standard cell potential. Some being negative, some being positive. Remember if you're using up electricity, you're consuming electricity, which means that your standard cell potential would be negative. That means that options B and C are out here, we have negative 0.75 volts versus negative 1.42 volts. Here D is the answer because not only is it negative in terms of its standard cell potential, it is the most negative. This would mean that it consumes or uses up the largest amount of electricity. So again, our final answer here would be option D.
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