If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

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

Lesson 5: Cell potentials under nonstandard conditions

# Galvanic cells and changes in free energy

Relationship between Gibbs free energy, reaction quotient Q, and cell voltage.

## Want to join the conversation?

• Where does the K= 1.58*10^37 come from?
• You can use ΔG° = -RT ln(Q) to find it
since we have:
ΔG° = -212 x 10^3 J
R = 8.314 J/Kmol
T = 298K

Although i got K = 1.45 x 10^37
(probably has to do withe rounding of ΔG°, it cant be nicely 212 KJ)

Otherwise, K is typically determined experimentally.
(1 vote)
• at , how do I know the number of electrons transferred? I'd like to solve for E myself to see that it's 0.98V but I don't know where to get n (number of electrons) from.
• n is the number of electrons in your half-cell reactions. In this case, n=2
• I am missing a whole bunch! I didn't understand a thing about what's going on here. So I went to the next section, Cell Potentials, which seems to give the foundation for understanding this video. So I'll come back to this one, later.

But, is it out of sequence? Should it be in the next section?
• If I'm ever lost in the sequence of the MCAT tutorials, I switch over to the physics/chem/org sections and usually find the missing videos.
• Can we consider the free energy here as the energy released due to the redox reaction and that it's utilized in transferring the electrons?
I just want to relate this to voltage = work/ q.
That in delta G= -nFE°, nF gives us the quantity of charge and E° is voltage. When we multiply these we get energy or work done to transfer charges.
• So does Q = K, the equilibrium constant in the last videos?
(1 vote)
• K is the expression of [products]/[reactants] at equilibrium.
Q is the same expression but at whatever time point you are looking at, let's say 4 minutes into a reaction.
If Q=K, the reaction is at equilibrium.
If Q<K, there are more reactants than at equilibrium so the reaction toward products will be favored.
If Q>K, there are more products than at equilibrium so the reverse reaction will be favored.
• Why do you always do the math with a calculator? Aren't these for MCAT prep? Anyways, any help on calculating ln 10,000 w/o a calculator?
(1 vote)
• These lectures are prepared to help students from around the world who are preparing to sit a range of different examinations. They're not specifically aimed at MCAT.