First Law of Thermodynamics
?E = q + w |or| ?U = q + w
System absorbs heat
q > 0
System evolves heat
q<0
Surroundings does work on system
w>0
System does work on surroundings
w<0
Specific Heat, C_sp_
q = m C_sp ?T ( T= (T_final - T_initial))
Molar Heat Capacity, C_n_
q = n C_n ?T ( T= (T_final - T_initial))
?G^o rxn = ?H^o rxn - T ?S^o rxn
?H^o = ?G^o + T ?S^o
G rxn = -T?S_universe
spontaneous change:
?H:"-" ?S:"+" = spontaneous at all temp
?H:"+" ?S:"-" = never spontaneous
?H:"-" ?S:"-" = spontaneous only at low temp
?H:"+" ?S:"+" = spontaneous only at high temp
Entropy
(Delta S) as a measurement of the randomness or disorder of a system
Factors that inc entropy
-When solid>liquid>gas
-An inc in particles present
-An inc in temp
+?S_surr= -?H / T
?S_u=?S_sys+?S_surr
?G=0
equilibrium
?G<0
spontaneous
?G>0
non-spont
Rate= +?product / ?t [(1/coefficient)]
Rate= -?reactant / ?t
1st order k has units of
s-1
2st order k has units of
L / mol s-1
if n=0
doubling [A] does not change the reaction rate
if n=1
doubling [A] doubles the reaction rate
if n=2
doubling [A] quadruples the reaction rate
zero order
rate= -k[A]^0= -k int rate=dA/dt= -kA*0= -k
first order
int rate= ln([A]I / [A]o)=kt
dA / dt= -kt^1= -kA
second order
int rate= 1 / [A]I - 1 / [A]o = kt
dA / dt = -kA^2
half life
693/k
k=Ae^(-Ea / RT)
Ea is the activation energy
R is the universal gas law constant
R = 8.31 x 10-3 kJ/K�mol
T is the absolute temperature
A is the proportionality constant called the frequency factor or preexponential factor
Arrhenius equation
ln(k)= -Ea/R (1/T)+ln(A)
Catalysts
increase the reaction rate by lowering the activation energy. It also neither created nor destroyed.