Cell Notation & The Nernst Equation

by Jules Bruno
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here in this example in states, the some notation for Redox reaction is given as the following at temperature of 2 98. Kelvin remember, when we're talking about some notation, we say it's easy, like a B C. So this represents are an ode, our break or physical break that separates the two solutions from each other and then our cathode. So here first it says right, the balance, half reactions occurring at the anote and the cathode. So we know what theano do. We have zinc solid going to make zinc two plus ion. Remember, we wanna put electrons on the more positive side. This side is neutral, cause Inc has no charge. Zinc here has a plus to charge. So discharges plus two, which means we would add two electrons to this side so that both sides are zero at the end. Then for the cathode, it's nickel two plus going to nickel solid again. We add electrons with a more positive side, so we'd add two electrons to this side. So this would be at the an ode. This would be at the cathode. If we combine those two together, that helps us to give the complete balance. Redox reaction. So bringing them both down. We have zinc solid. Gives us zinc two plus ion plus two electrons. Then we have two electrons, plus nickel. Two plus gives us nickel solid. So what happens here? Both electrons cancel out, and what's left at the end is our overall equation. So zinc solid plus nickel two plus gives us zinc two plus plus nickel solid. Remember, your ions are acquis in solution, and the neutral metal forms are solids. Now that we know that we can determine our self potential, remember self potential. This means under standard conditions, equals cathode minus an ode. Yeah, here, I'm giving you the values. I didn't give them to you beforehand, but now I am So we said that the cathode had the nickel and here the value for nickel. It's self potentials 0.23 volts and then the ano deals with zinc. Its value is negative. 76 volts. So remember it's cathode minus an Oh, so that's negative. 00.23 volts minus ah minus 0.76 volts, Remember, minus of a minus really means positive. So this negative 0.23 volts plus 0. volts, which comes out to a positive 0.54 volts. For the next question, we have to calculate the maximum electrical work that could be produced by this cell. So just realize when they're asking for electrical work, they're really asking about Gibbs Free Energy and that connects to sell potential in this form. So Gibbs free energy equals negative end times f times SL and is the number of electrons that are transferred. So basically the electrons that cancel out which would be to so n would be two electrons involved in this reaction. So two moles of Electrons F is known as Faraday's constant. So here Faraday's constant is 485 cool ums per mole of electrons. Sometimes your professor will just round it off to 96,500. That's fine, too, but here I just wanna be as accurate as possible. So that would be on negative will be 96, columns per mole of electrons, so most of electrons cancel out. Now we have columns and realize here that when we say volts because this is in volts, volts equals jewels over Colom's. So this is 0.50 for Jules over. Colom's so cool it was canceled. So we're gonna have jewels. So this comes out to negative 1000 and four negative. 104,204 jewels as our answer Now, Finally, our last portion asked us to calculate the reacted quotient for this cell and the cell potential under nonstandard conditions. So we need room for this guys. So let me take myself out of the equation out of the picture. Remember, Q is you're reacting question or reaction questioned. It's just equal toe products. Overreacting. It's it ignores solids and liquids. So what we have to do is we look at the overall equation that we have here again. We ignore solids and liquids. So here this is a quiz. So we're gonna keep this around. This is a quick we're gonna keep it around. The other two are solid, so ignore them. So this equals zinc two plus ion over nickel two plus ion. And what values do we plug in here when we go back up here? And look, I gave you the concentration for each ion. Those are the numbers. They're gonna plug in there to find que So that's 0.37 divided by 0.59 which comes out to 6. 119 That's cute. Now that you know Q, we can answer the second portion. We have to find the self potential under nonstandard conditions. Remember, standard conditions really means one atmosphere. Ah, concentration of one Mueller and 25 degrees Celsius. That's what standard conditions are, and the concentrations here are not one Moeller. So that's what we're looking at under nonstandard conditions. And if we're looking for under nonstandard conditions, that means we use what's called the nursed equation. So in the nurse equation, it's self potential. Under nonstandard conditions equals self potential under standard conditions minus 0.5916 over the number of electrons transferred times log of cute. So we found himself. Potential understanding conditions earlier was 54 volts, minus 0.591 6/2 electrons transferred times Log of Q, which we just found A 6. When we punch this into our calculator, gives us point 516 volts as our final answer. So As you can see, just with a simple some notation, There's a lot of information that we can derive from it. We can figure out the overall equation. What's happening at the Catherine the An ode gives free energy equilibrium constants. So there's a lot of information that we went over here. Remember each one of the situations, what it entailed for us to do on our part, yeah.