Spontaneity
STATE FUNCTION PATH FUNCTION
ENTHALPY THERMOCHEMISTR
H = U + ngRT
ng = 0, H = U
Properties which depend only Depends on path or process. ng > 0, H > U
on initial and final state of system as well as initial and final state ng < 0, H < U
1) Heat of Reaction ( Hrxn.)
& do not depend on process or path of the system
All exothermic process are spontaneous
THERMODYNAMICS
Hrxn.= Hproducts - Hreactants
e.g. U, H , S etc. e.g. work, heat
2) Heat of Formation
THERMODYNAMIC PROPERTIES ENTROPY Heat Change in formation of 1 mole of substance at 298 K and 1 atm Pressu
(standard enthalpy of formation )
1 3
N2 + H2 NH3
Sgas > Sliquid > Ssolid 2 2
A + B C + D
PHYSI
EXTENSIVE INTENSIVE
a b c d
ENTROPY CHANGE
1) Isothermal
Properties which are dependent Properties which are independent Hreaction= Heat of formation of products- Heat of formation of reactants
V2 P1
S = nR ln = nR ln = ( c + d ) - ( a + b)
of matter (size & mass)present of matter(size & mass) present in V1 P2
in system system Standard enthalpy of formation ( 298 K, 1 atm) of element at it‛s standar
e.g. Mass, volume, Internal energy e.g. Pressure, temperature, 2) Isochoric ( P O T)
state is zero e.g.,
heat capacity, Entropy, Enthalpy Melting point, density,Specific heat T2 P2
S = nCv ln = nCv ln O2 (g) = 0 Cl2 (g) = 0 Br (g) = 0 Br2 (l) = 0
etc. Surface tension etc P1
T1
3) Isobaric
3) Enthalpy of Combustion (1 mole, 298 K )
WORK dm3or L
S = nCp ln
T2
T1
= nCp ln
V2
V1 (standard enthalpy of combust
W = P V = nRT
10-3 10-3 CH4 + 2O2 CO2 + 2H2O ; H combustion
WALLA
P Pascal 1 atm = 1.01 x 10 Pa
5
Stotal > 0, Spontaneous
Cm3 m3
W =Joule 1 L atm = 101 J
V m3 Stotal = 0, Equilibrium A + B C + D
10-6 Enthalpy of a b c d
Stotal < 0, Non-spontaneous
combustion:
FIRST LAW OF THERMODYNAMICS Hreaction= Heat of combustion of reactants - Heat of combustion of produ
= ( a + b) - ( c + d )
GIBBS’S FREE ENERGY
G = H -T S
(Based on Law of conservation of energy) G < 0 Or (-)ve, Spontaneous
U = q+ W 4) Heat of Neutralisation ( H = (-)ve)
G > 0 Or (+)ve, Non-spontaneous
G = 0 , Equilibrium
HCl + NaOH NaCl + H2O ; Hneutalisation
S.A + S.B H = -13.7 k Cal = - 57 kJ
S.A + S.B > (S.A/ S.B + W.A/W.B)- > W.A+W.B ( Order of H neut
Equilibrium Temperature
SIGN CONVENTION
H
W(Compression) W(Expansion) Te =
S
(+)ve system (-)ve
STATE FUNCTION PATH FUNCTION
ENTHALPY THERMOCHEMISTR
H = U + ngRT
ng = 0, H = U
Properties which depend only Depends on path or process. ng > 0, H > U
on initial and final state of system as well as initial and final state ng < 0, H < U
1) Heat of Reaction ( Hrxn.)
& do not depend on process or path of the system
All exothermic process are spontaneous
THERMODYNAMICS
Hrxn.= Hproducts - Hreactants
e.g. U, H , S etc. e.g. work, heat
2) Heat of Formation
THERMODYNAMIC PROPERTIES ENTROPY Heat Change in formation of 1 mole of substance at 298 K and 1 atm Pressu
(standard enthalpy of formation )
1 3
N2 + H2 NH3
Sgas > Sliquid > Ssolid 2 2
A + B C + D
PHYSI
EXTENSIVE INTENSIVE
a b c d
ENTROPY CHANGE
1) Isothermal
Properties which are dependent Properties which are independent Hreaction= Heat of formation of products- Heat of formation of reactants
V2 P1
S = nR ln = nR ln = ( c + d ) - ( a + b)
of matter (size & mass)present of matter(size & mass) present in V1 P2
in system system Standard enthalpy of formation ( 298 K, 1 atm) of element at it‛s standar
e.g. Mass, volume, Internal energy e.g. Pressure, temperature, 2) Isochoric ( P O T)
state is zero e.g.,
heat capacity, Entropy, Enthalpy Melting point, density,Specific heat T2 P2
S = nCv ln = nCv ln O2 (g) = 0 Cl2 (g) = 0 Br (g) = 0 Br2 (l) = 0
etc. Surface tension etc P1
T1
3) Isobaric
3) Enthalpy of Combustion (1 mole, 298 K )
WORK dm3or L
S = nCp ln
T2
T1
= nCp ln
V2
V1 (standard enthalpy of combust
W = P V = nRT
10-3 10-3 CH4 + 2O2 CO2 + 2H2O ; H combustion
WALLA
P Pascal 1 atm = 1.01 x 10 Pa
5
Stotal > 0, Spontaneous
Cm3 m3
W =Joule 1 L atm = 101 J
V m3 Stotal = 0, Equilibrium A + B C + D
10-6 Enthalpy of a b c d
Stotal < 0, Non-spontaneous
combustion:
FIRST LAW OF THERMODYNAMICS Hreaction= Heat of combustion of reactants - Heat of combustion of produ
= ( a + b) - ( c + d )
GIBBS’S FREE ENERGY
G = H -T S
(Based on Law of conservation of energy) G < 0 Or (-)ve, Spontaneous
U = q+ W 4) Heat of Neutralisation ( H = (-)ve)
G > 0 Or (+)ve, Non-spontaneous
G = 0 , Equilibrium
HCl + NaOH NaCl + H2O ; Hneutalisation
S.A + S.B H = -13.7 k Cal = - 57 kJ
S.A + S.B > (S.A/ S.B + W.A/W.B)- > W.A+W.B ( Order of H neut
Equilibrium Temperature
SIGN CONVENTION
H
W(Compression) W(Expansion) Te =
S
(+)ve system (-)ve
