is H > 0 and S > 0
x --> X+ + e-
non-spontaneous is...
thermodynamically unfavorable
is H < 0 and S > 0
spontaneous at all Temps, delta G <0
if a reaction is kinetically favorable
it has k>1, relatively low activation energy
galvanic cell vs electrolytic cell
galvanic = anode is negative and cathode is positive
electrolytic = anode is positive and cathode is negative
cell potential, Ecell, electromotive force (emf)
delta G and the energy of the product is lower than that of the reactants
1. G = negative = k>1; G = positive = k
delta S =
(sum of S products) - (sum of S reactants)
DO NOT FORGET TO ACCOUNT FOR THE MOLES IN THE REACTION!!!
1st law of thermodynamics
in an isolated system energy can neither be created or destroyed; only transferred or converted, meaning E lost = negative E gained
V = IR
voltage = current (amps) * resistance (ohms)
as temperature goes to zero, entropy approaches a constant value
T=100k
spontaneous, low temperature, T delta S is small
2nd law of thermodynamics
entropy of an isolated system is never decreasing, only if it is in a 2 or more system
exergonic reaction
products have less energy than reactants, spontaneous, graph will end lower than it started
cathode
reduction happens, gaining electrons
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!!
how a reaction that is thermodynamically unfavorable occur
a reaction can be coupled with a reaction that is favorable to push it forward
Examples:
- photosynthesis
- ATP
- Charging a battery with electricity
what is Gibb's free energy
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.
galvanic cell
degrees of freedom of a molecule
volumes proportionality with entropy
as V goes up, so does S
as the more temperature, the more energy, the mor entropy
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
charging a battery vs using a battery
charging = non-spontaneous
using = spontaneous
S = entropy
G = Gibbs free energy
H = heat energy
how K and G relate to each other
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
anode
oxidation happens, losing electrons
y + z --> Y+ + Z- (G<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
