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### Course: AP®︎/College Chemistry>Unit 14

Lesson 5: Cell potentials under nonstandard conditions

# Nernst equation

Deriving a few different forms of the Nernst equation, the relationship between Gibbs free energy and reaction quotient Q.  Created by Jay.

## Want to join the conversation?

• As far as the MCAT goes, are we going to be expected to have all of these equations memorized? Does anyone know? And are there any tips or tricks for remembering different equations?
(1 vote)
• The Nernst equation will be given to you on the MCAT if necessary.
• Why is the gas constant used?
• Constants are used is most linear equations. They are used to describe the magntiude of an effect of increase/decreasing on variable on the other.
• But why is cell potential changes with concentrations. In another video, Jay says that voltage is intensive property. Then why does it depends on concentration. Can anyone explain me where I misunderstood?
• Hi, in all of my books nerst equation is E = E0 + ( 0.0592/2 ) + logQ; Why are you substract 0.0592/2 from E0 instead of add it, does it depend of E0? I am little bit confused.
• If i'm right, in Gibb's free energy equation, we use Q as Conc. of products/Conc. of Reagents, so in this kind of equation Conc. of cathode ions (which are reducted)/ Conc. of anode ions (which are oxidated), so [Cu2+]/[Zn2+], obtaining an higher value of k as the reaction flows.
In nerst equation, the concentrations are swapped, so [Conc of anode]/[Conc. of cathode], changing the sign from - to +.
Hope i'm right!
• If I have a lithium ion battery (for arguments sake let it be lithium-cobalt-oxide), does the Nernst equation apply? I'm trying to find mathematically what changing the temperature does to the performance of the battery. Thanks
• Why is n a constant in both equations?
(1 vote)
• n is the number of moles of electrons transferred during the reaction.
Both equations refer to the same reaction, so n is constant in each equation.
• In the Nernst equation..I am confused about the n variable. Some sources have this variable listed as "z", or the valence/charge of the ion. Here it is considered the # of moles of electrons transferred in the reaction. Is this the same? Am I missing something?
(1 vote)
• The Nernst equation is used to determine the potential of a cell.
n or z (from Zahl for "number") is the number of moles of electrons transferred in the cell reaction.