is H < 0 and S < 0
T=100k
spontaneous, low temperature, T delta S is small
is H < 0 and S > 0
spontaneous at all Temps, delta G <0
if a reaction is thermodynamically favorable
delta G and the energy of the product is lower than that of the reactants
1. G = negative = k>1; G = positive = k
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
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
entropy
degrees of freedom of a molecule
1st law of thermodynamics
reduction happens, gaining electrons
how K and G relate to each other
S = entropy
G = Gibbs free energy
H = heat energy
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
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.
products have less energy than reactants, spontaneous, graph will end lower than it started
oxidation half-reaction
x --> X+ + e-
anode
oxidation happens, losing electrons
as temperature goes to zero, entropy approaches a constant value
thermodynamically unfavorable
overall cell reaction
y + z --> Y+ + Z- (G<0)
is H > 0 and S > 0
T = 500k
spontaneous, high temperature, T delta S is large
galvanic cell
voltage equation
delta S =
(sum of S products) - (sum of S reactants)
DO NOT FORGET TO ACCOUNT FOR THE MOLES IN THE REACTION!!!
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
volumes proportionality with entropy
as V goes up, so does S
as the more temperature, the more energy, the mor entropy
galvanic cell vs electrolytic cell
1 joule of work / coulomb of charge transferred
J/C = units
charging = non-spontaneous
using = spontaneous
