Cell Potential and Equilibrium - Video Tutorials & Practice Problems
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1
concept
∆Eº, ∆G and K Formulas
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We're going to say that Gibbs free energy, which is delta G not. So we're talking about Standard Gibbs free energy is the bridge to the standard cell potential which here that is E knot sub cell and the equilibrium constant K. Now this connection could be seen in the following way. So on the left side, we have the connection between our standard cell potential and gives free energy. Here, we're talking about Standard gives free energy. It is equal to negative N times F times our standard self potential. Here we'd say that our standard gives free energy is in units of kilojoules and is just the number of moles transferred within our redox reaction. F is fair constant, which remember is 96,485 Coombs per moles of electrons. And then our standard cell potential here will be in units of volts abbreviated V. On the right side, we have the connection between our equilibrium constant K and our standard gift free energy. Here we'd say that standard gives free energy. The change in it is equal to negative RT LNK. So here R is our gas constant which is 8.314 joules over moles times KT here equals temperature. In Kelvin k here is just our equilibrium constant. So we say that Gibbs free energy equals this equation. We say that gives free energy equals this equation. Since Gibbs free energy equals both equations, they must be equal to one another. So in the middle here, we can say that the connection between our standard cell potential and our equilibrium constant K is negative N times F times standard cell potential equals negative RT L and K. Now here, from this middle equation, we can isolate our standard cell potential. So here we wanna isolate this variable here to do that, you divide out negative N times F from both sides. So they cancel out here on the left side, the negative signs cancel out. So at the end, we'd get here that our standard cell potential equals RT over N times F times Ln of K. This represents the connection between our standard cell potential. You're equally recons in its simplified form.
2
example
Cell Potential and Equilibrium Example
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2m
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Here in this example question, it says a certain electrochemical reaction involves the transferring of four electrons. If the value of its equilibrium constant is 2.50 times 10 to the 12 at 25 °C, calculate the standard cell potential. So we know the equation that connects our standard cell potential. And our equilibrium constant is standard cell potential equals our gas constant. R times our temperature in Kelvin divided by the num the moles of electrons transferred times 30 days constant. And this will be multiplied by Allen of K. So what we do now is we plug in the values that we have R is 8.314 Joel over moles times K. Our temperature here needs to be in Kelvin. So you're gonna add 2 73.15 here to give us 2 98.15 Kelvin. So there goes our temperature and is the moles of electrons transferred, which is four moles of electrons transferred be content is 96,045 Kums per moles of electrons. And then Allen of K which is 2.50 times 10 to the 12. Here, when we look at the units that are canceling out. We see that what cancels out multiple electrons cancel out. Kelvins cancel out K here has no units in itself. And then at the end, what we're gonna see is we're gonna have jewels, the per Coolum per moles of this uh question. So here when we do that, we're gonna get point 18335 joules per Coolum per mole, joules per Coolum is the same thing as volts. Now, here we'll do it just a 36 fix. So that's gonna give me 0.183 volts. And here it's important to realize that it's positive. Uh 0.183 volts. We know that our cell potential here is positive since our equilibrium constant is greater than one. So this will be our final answer.
3
Problem
Problem
Calculate the equilibrium constant for the following reaction at 25ºC.
Fe (s) + I2 (s) → Fe2+ (aq) + 2 I – (aq)
Given the following reduction potentials:
Fe2+(aq) + 2 e– →. Fe(s) E°red = – 0.45 V
I2 (s) + 2 e– →. 2 I – (aq) E°red = + 0.54 V
A
1.15 x 1011
B
2.96 x 1033
C
3.91 x 105
D
8.17 x 10-3
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