Thermodynamics and Kinetics

Thermodynamics and Kinetics

 

The following tables were made using information in the following references:

 

Smith's Organic Chemistry ISBN=978-0-07-304986-1 or 978-0-07-304986-7.

McMurry's ISBN=0-13-187748-8.

 

Items marked with ? need checking.

 

Term	Meaning
T	temperature in Kelvin
H	enthalpy
S	entropy
G	Gibbs Free Energy
ΔH	change in enthalpy
ΔS	change in entropy
ΔG	change in Gibbs Free Energy
ΔG	ΔH-TΔS
	memorize

 

Term	Meaning
ΔH	energy of bonds formed in products - energy of bonds broken in reactants ?
ΔH	sum of ΔH's of bonds broken in reactants - sum of ΔH's of bonds formed in products ?
ΔH<0	products have stronger bonds than reactants ?
ΔH<0	favors product formation for small T
ΔH>0	endothermic reaction
ΔH>0	heat is a reactact
ΔH>0	absorbs heat
ΔH>0	reaction favored at high temperature ?
ΔH<0	exothermic reaction
ΔH<0	heat is a product
ΔH<0	releases heat
ΔH<0	reaction favored at low temperature
	memorize

 

Term	Meaning
low entropy	solids
high entropy	gases
ΔS>0	for solid to liquid or liquid to gas
ΔS<0	for gas to liquid or liquid to solid
ΔS>0	for less moles of reactants than products
ΔS<0	for more moles of reactants than products
ΔS>0	if disorder rises
ΔS<0	if disorder falls
ΔS>0	favors product formation
ΔS>0	products have more disorder than reactants
ΔS<0	products are more ordered than reactants
S for the universe	it always rises
ΔS for the universe	always positive
	memorize

 

Term	Meaning
ΔG<0	spontaneous
ΔG<0	releases Free Energy
ΔG<0	exergonic process
ΔG>0	non-spontaneous
ΔG>0	absorbs Free Energy
ΔG>0	endergonic process
ΔG>0	more stable reactants
ΔG<0	more stable products
ΔG	sum of G's for products - sum of G's for reactants
ΔG	-RT ln K
ΔG<0	favors product formation
	memorize

 

Term	Meaning
Ea	Activation Energy
Ea	always positive
big Ea	slow reaction
small Ea	fast reaction
high concentration	fast reaction
high temperature	fast reaction
kinetics	how fast reactions occur. reaction rates.
thermodynamics	energies and equilibrium values
catalyst	alters Ea but not ΔG,ΔH,K
catalyst	alters kinetics but not thermodynamics
catalyst	alters the rate equilibrium is established
catalyst	does not alter equilibrium values
high pressure	favors side of reaction with less moles of gas
low pressure	favors side of reaction with more moles of gas
raise concentration of reactants	favors forward reaction
lower concentration of products	favors forward reaction
raise concentration of products	favors reverse reaction
lower concentration of reactants	favors reverse reaction
	memorize

 

Term	Meaning
K	equilibrium constant
K	concentrations of products / concentrations of reactants
K	([M]m [N]n)/([A]a [B]b) for the reaction a A + b B <=> m M + n N
K>1	favors products at equilibrium
K<1	favors reactants at equilibrium
K<<1	virtually no reaction occurs
K<0.001	virtually no reaction occurs
K>>1	reaction practically goes to completion
K>1000	reaction practically goes to completion
	memorize

 

What about K_c vs. K_p for gas reactions? For the reaction a A + b B <=> m M + n N aren't they:

 

K_c=(M^m Nⁿ)/(A^a B^b)

 

K_p=(P_M^m P_Nⁿ)/(P_A^a P_B^b)

 

where P_M is the partial pressure of the gas M, and

 

P_M=MRT

 

  by the ideal gas law. This gives:

 

K_p=K_c(RT)^m+n-a-b

 

For the reaction a A + b B <=> m M + n N, what are the rates in the forward and reverse directions? Aren't they like below ?

 

-1/a dA/dt = -1/b dB/dt = 1/m dM/dt = 1/n dN/dt = k1 A^a B^b - k2 M^m Nⁿ

 

It would be good to add 0th, 1st, and 2nd order reaction kinetics here too.

 

Also discuss the relationship between the equilibrium constant and the forward and reverse rates of a reaction.