overall cell reaction
y + z --> Y+ + Z- (G<0)
cell potential, Ecell, electromotive force (emf)
1 joule of work / coulomb of charge transferred
J/C = units
if a reaction is thermodynamically favorable
voltage equation
entropy
degrees of freedom of a molecule
(sum of S products) - (sum of S reactants)
DO NOT FORGET TO ACCOUNT FOR THE MOLES IN THE REACTION!!!
is H < 0 and S < 0
how do you calculate Gibbs free energy
delta G = delta H - (T * delta S)
gibbs free energy = enthalpy - (temperature times entropy)
*note T is in kelvin, not Celsius
oxidation happens, losing electrons
2nd law of thermodynamics
entropy of an isolated system is never decreasing, only if it is in a 2 or more system
as matter disperses, entropy increase, so, going from solid to liquid to gas would increase entropy, whilst going from gas to liquid to solid would decrease it
in an isolated system energy can neither be created or destroyed; only transferred or converted, meaning E lost = negative E gained
non-spontaneous is...
galvanic cell vs electrolytic cell
galvanic = anode is negative and cathode is positive
electrolytic = anode is positive and cathode is negative
oxidation half-reaction
x --> X+ + e-
spontaneous at all Temps, delta G <0
as temperature goes to zero, entropy approaches a constant value
G = negative = k>1
G = positive = k<1
k is close to 1, G is close to zero
k is far from 1, G is far from zero
the energy of a system related to changes in enthalpy and entropy, at a constant temperature.
basically implies that the system is at 1 atm and using 1 M solutions.
is H > 0 and S > 0
T = 500k
spontaneous, high temperature, T delta S is large
a reaction can be coupled with a reaction that is favorable to push it forward
Examples:
- photosynthesis
- ATP
- Charging a battery with electricity
Cell potential equation
Ecell = E (cathode) - E (anode)
IMPORTANT: if the reaction gets reversed (in order to balance, sometimes it will need to be reversed), the sign of the Ecell must switch, however if it gets multiplied (in order to balance) IT REMAINS THE SAME!!
if a reaction is kinetically favorable
it has k>1, relatively low activation energy
G, S, H
S = entropy
G = Gibbs free energy
H = heat energy
exergonic reaction
products have less energy than reactants, spontaneous, graph will end lower than it started
charging a battery vs using a battery
cathode
reduction happens, gaining electrons
galvanic cell
volumes proportionality with entropy
as V goes up, so does S
as the more temperature, the more energy, the mor entropy
