unit 9 must knows duel

if a reaction is thermodynamically favorable

2nd law with entropy

galvanic cell chemical energy is converted to electrical energy with spontaneous redox reaction Voltage consists of oxidizing agent in one compartment that pulls electrons through a wire from a reducing agent

if a reaction is kinetically favorable it has k>1, relatively low activation energy

2nd law of thermodynamics

a reaction can be coupled with a reaction that is favorable to push it forward Examples: - photosynthesis - ATP - Charging a battery with electricity

(sum of S products) - (sum of S reactants) DO NOT FORGET TO ACCOUNT FOR THE MOLES IN THE REACTION!!!

volumes proportionality with entropy

entropy

overall cell reaction y + z --> Y+ + Z- (G<0)

cathode reduction happens, gaining electrons

G, S, H S = entropy G = Gibbs free energy H = heat energy

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.

oxidation half-reaction x --> X+ + e-

is H < 0 and S > 0 spontaneous at all Temps, delta G <0

1st law of thermodynamics

is H > 0 and S > 0

T=100k spontaneous, low temperature, T delta S is small

cell potential, Ecell, electromotive force (emf) 1 joule of work / coulomb of charge transferred J/C = units

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

voltage equation V = IR voltage = current (amps) * resistance (ohms)

how do you calculate Gibbs free energy

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!!

charging a battery vs using a battery charging = non-spontaneous using = spontaneous

anode

exergonic reaction

non-spontaneous is... thermodynamically unfavorable

galvanic cell vs electrolytic cell

3rd law of thermodynamics as temperature goes to zero, entropy approaches a constant value

volumes proportionality with entropy as V goes up, so does S as the more temperature, the more energy, the mor entropy

cell potential, Ecell, electromotive force (emf) 1 joule of work / coulomb of charge transferred J/C = units

if a reaction is kinetically favorable it has k>1, relatively low activation energy

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

entropy of an isolated system is never decreasing, only if it is in a 2 or more system

if a reaction is thermodynamically favorable

entropy degrees of freedom of a molecule

voltage equation

exergonic reaction products have less energy than reactants, spontaneous, graph will end lower than it started

reduction happens, gaining electrons

T = 500k spontaneous, high temperature, T delta S is large

oxidation half-reaction x --> X+ + e-

anode

3rd law of thermodynamics as temperature goes to zero, entropy approaches a constant value

how a reaction that is thermodynamically unfavorable occur

S = entropy G = Gibbs free energy H = heat energy

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.

(sum of S products) - (sum of S reactants) DO NOT FORGET TO ACCOUNT FOR THE MOLES IN THE REACTION!!!

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

spontaneous at all Temps, delta G <0

thermodynamically unfavorable

galvanic = anode is negative and cathode is positive electrolytic = anode is positive and cathode is negative

how K and G relate to each other

is H < 0 and S < 0 T=100k spontaneous, low temperature, T delta S is small

overall cell reaction 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

charging a battery vs using a battery

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