Cheat sheet: Thermodynamics | Chemistry Class 11 - NEET PDF Download

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Thermodynamics Cheat Sheet - Class 11
CBSE
1. Thermodynamic T erms
S ystem and Surroundings
• S ystem: Part of the universe under study .
• Surroundings: Everything outside the system.
• Universe: S ystem + Surroundings
Types of S ystems
Type Matter Exchange Energy Exchange Example
Open Y es Y es Reactants in an open beak er
Closed No Y es Reactants in a sealed copper vessel
Isolated No No Reactants in a thermos flask
State Functions
Depend only on the state, not the path: Internal Energy (U ), Enthalp y (H ), Pres-
sure (p ), V olume (V ), T emper ature (T ).
Internal Energy (U )
T otal energy of the system (chemical, electrical, mechanical).
Change in Internal Energy: ?U =q+w
q : Heat abs orbed b y system (+ve), released (–ve).
w : W ork done on system (+ve), b y system (–ve).
2. First Law of Thermodynamics
Energy of an isolated system is constant. Energy cannot be created or destro yed.
?U =q+w
1
Page 2


Thermodynamics Cheat Sheet - Class 11
CBSE
1. Thermodynamic T erms
S ystem and Surroundings
• S ystem: Part of the universe under study .
• Surroundings: Everything outside the system.
• Universe: S ystem + Surroundings
Types of S ystems
Type Matter Exchange Energy Exchange Example
Open Y es Y es Reactants in an open beak er
Closed No Y es Reactants in a sealed copper vessel
Isolated No No Reactants in a thermos flask
State Functions
Depend only on the state, not the path: Internal Energy (U ), Enthalp y (H ), Pres-
sure (p ), V olume (V ), T emper ature (T ).
Internal Energy (U )
T otal energy of the system (chemical, electrical, mechanical).
Change in Internal Energy: ?U =q+w
q : Heat abs orbed b y system (+ve), released (–ve).
w : W ork done on system (+ve), b y system (–ve).
2. First Law of Thermodynamics
Energy of an isolated system is constant. Energy cannot be created or destro yed.
?U =q+w
1
W o rk (Pressure-V olume)
Irreversible W ork: w = -p
ex
?V
Reversible Isothermal W ork (Ideal Gas): w
rev
= -nRT ln
(
V
f
V
i
)
Free Expansion: w =0 (p
ex
=0 )
Heat
q =C?T (C : Heat capacity)
Molar Heat Capacity: C
m
=C/n
Specific Heat: q =m·c·?T
3. Enthalp y (H )
H =U +pV
At constant pressure: ?H =?U +p?V
F or gases: ?H =?U +?n
g
RT
?n
g
: Moles of gaseous products – moles of gaseous reactants
Heat Capacity Relationship
F or ideal gas: C
p
-C
v
=R
4. Calorimetry
?U Measurement
Bomb Calorimeter (Constant V olume): q
v
=?U =C
v
?T
?H Measurement
Constant Pressure Calorimeter: q
p
=?H
2
Page 3


Thermodynamics Cheat Sheet - Class 11
CBSE
1. Thermodynamic T erms
S ystem and Surroundings
• S ystem: Part of the universe under study .
• Surroundings: Everything outside the system.
• Universe: S ystem + Surroundings
Types of S ystems
Type Matter Exchange Energy Exchange Example
Open Y es Y es Reactants in an open beak er
Closed No Y es Reactants in a sealed copper vessel
Isolated No No Reactants in a thermos flask
State Functions
Depend only on the state, not the path: Internal Energy (U ), Enthalp y (H ), Pres-
sure (p ), V olume (V ), T emper ature (T ).
Internal Energy (U )
T otal energy of the system (chemical, electrical, mechanical).
Change in Internal Energy: ?U =q+w
q : Heat abs orbed b y system (+ve), released (–ve).
w : W ork done on system (+ve), b y system (–ve).
2. First Law of Thermodynamics
Energy of an isolated system is constant. Energy cannot be created or destro yed.
?U =q+w
1
W o rk (Pressure-V olume)
Irreversible W ork: w = -p
ex
?V
Reversible Isothermal W ork (Ideal Gas): w
rev
= -nRT ln
(
V
f
V
i
)
Free Expansion: w =0 (p
ex
=0 )
Heat
q =C?T (C : Heat capacity)
Molar Heat Capacity: C
m
=C/n
Specific Heat: q =m·c·?T
3. Enthalp y (H )
H =U +pV
At constant pressure: ?H =?U +p?V
F or gases: ?H =?U +?n
g
RT
?n
g
: Moles of gaseous products – moles of gaseous reactants
Heat Capacity Relationship
F or ideal gas: C
p
-C
v
=R
4. Calorimetry
?U Measurement
Bomb Calorimeter (Constant V olume): q
v
=?U =C
v
?T
?H Measurement
Constant Pressure Calorimeter: q
p
=?H
2
5. Enthalp y Changes
Reaction Enthalp y (?
r
H )
?
r
H =
?
a
i
H
m
( products)-
?
b
i
H
m
( reactants)
Standard Enthalp y (?H
?
)
Substances in standard state (pure form, 1 bar , usually 298 K).
Types of Enthalp y Changes
Type Definition Example
Fusion (?
fus
H
?
) Enthalp y to melt 1 mol of solid H
2
O(s) H
2
O(l); 6.00 kJ/mol
V aporization (?
vap
H
?
) Enthalp y to vaporize 1 mol of
liquid
H
2
O(l) H
2
O(g); 40.79
kJ/mol
Sublimation (?
sub
H
?
) Enthalp y to sublime 1 mol of
solid
CO
2
(s) CO
2
(g); 25.2 kJ/mol
F ormation (?
f
H
?
) Enthalp y to form 1 mol from
elements
C(gr aphite) +
2
H
2
(g)
CH
4
(g); –74.81 kJ/mol
Combustion (?
c
H
?
) Enthalp y for complete com-
bustion of 1 mo l
C
4
H
10
(g) +
13
2
O
2
(g)
4
CO
2
(g) +
5
H
2
O(l); –2658
kJ/mol
Atomization (?
a
H
?
) Enthalp y to form gaseous
atoms
H
2
(g)
2
H(g); 435 kJ/mol
Bond Enthalp y Energy to break/mak e bo nds H–H: 435 kJ/mol
Lattice Enthalp y Enthalp y to dissociate 1 mol of
ionic solid
NaCl(s) Na
+
(g) + Cl
–
(g);
788 kJ/mol
Solution (?
sol
H
?
) Enthalp y to dissolve 1 mol in
solvent
NaCl(s) Na
+
(aq) + Cl
–
(aq);
+4 kJ/mol
Dilution Enthalp y change on adding
more solvent
HCl ·
25
aq HCl ·
40
aq; –0.76
kJ/mol
6. Hess’ s Law
Enthalp y change is same whether reaction occurs in one or multiple steps.
?
r
H =?
r
H
1
+?
r
H
2
+...
3
Page 4


Thermodynamics Cheat Sheet - Class 11
CBSE
1. Thermodynamic T erms
S ystem and Surroundings
• S ystem: Part of the universe under study .
• Surroundings: Everything outside the system.
• Universe: S ystem + Surroundings
Types of S ystems
Type Matter Exchange Energy Exchange Example
Open Y es Y es Reactants in an open beak er
Closed No Y es Reactants in a sealed copper vessel
Isolated No No Reactants in a thermos flask
State Functions
Depend only on the state, not the path: Internal Energy (U ), Enthalp y (H ), Pres-
sure (p ), V olume (V ), T emper ature (T ).
Internal Energy (U )
T otal energy of the system (chemical, electrical, mechanical).
Change in Internal Energy: ?U =q+w
q : Heat abs orbed b y system (+ve), released (–ve).
w : W ork done on system (+ve), b y system (–ve).
2. First Law of Thermodynamics
Energy of an isolated system is constant. Energy cannot be created or destro yed.
?U =q+w
1
W o rk (Pressure-V olume)
Irreversible W ork: w = -p
ex
?V
Reversible Isothermal W ork (Ideal Gas): w
rev
= -nRT ln
(
V
f
V
i
)
Free Expansion: w =0 (p
ex
=0 )
Heat
q =C?T (C : Heat capacity)
Molar Heat Capacity: C
m
=C/n
Specific Heat: q =m·c·?T
3. Enthalp y (H )
H =U +pV
At constant pressure: ?H =?U +p?V
F or gases: ?H =?U +?n
g
RT
?n
g
: Moles of gaseous products – moles of gaseous reactants
Heat Capacity Relationship
F or ideal gas: C
p
-C
v
=R
4. Calorimetry
?U Measurement
Bomb Calorimeter (Constant V olume): q
v
=?U =C
v
?T
?H Measurement
Constant Pressure Calorimeter: q
p
=?H
2
5. Enthalp y Changes
Reaction Enthalp y (?
r
H )
?
r
H =
?
a
i
H
m
( products)-
?
b
i
H
m
( reactants)
Standard Enthalp y (?H
?
)
Substances in standard state (pure form, 1 bar , usually 298 K).
Types of Enthalp y Changes
Type Definition Example
Fusion (?
fus
H
?
) Enthalp y to melt 1 mol of solid H
2
O(s) H
2
O(l); 6.00 kJ/mol
V aporization (?
vap
H
?
) Enthalp y to vaporize 1 mol of
liquid
H
2
O(l) H
2
O(g); 40.79
kJ/mol
Sublimation (?
sub
H
?
) Enthalp y to sublime 1 mol of
solid
CO
2
(s) CO
2
(g); 25.2 kJ/mol
F ormation (?
f
H
?
) Enthalp y to form 1 mol from
elements
C(gr aphite) +
2
H
2
(g)
CH
4
(g); –74.81 kJ/mol
Combustion (?
c
H
?
) Enthalp y for complete com-
bustion of 1 mo l
C
4
H
10
(g) +
13
2
O
2
(g)
4
CO
2
(g) +
5
H
2
O(l); –2658
kJ/mol
Atomization (?
a
H
?
) Enthalp y to form gaseous
atoms
H
2
(g)
2
H(g); 435 kJ/mol
Bond Enthalp y Energy to break/mak e bo nds H–H: 435 kJ/mol
Lattice Enthalp y Enthalp y to dissociate 1 mol of
ionic solid
NaCl(s) Na
+
(g) + Cl
–
(g);
788 kJ/mol
Solution (?
sol
H
?
) Enthalp y to dissolve 1 mol in
solvent
NaCl(s) Na
+
(aq) + Cl
–
(aq);
+4 kJ/mol
Dilution Enthalp y change on adding
more solvent
HCl ·
25
aq HCl ·
40
aq; –0.76
kJ/mol
6. Hess’ s Law
Enthalp y change is same whether reaction occurs in one or multiple steps.
?
r
H =?
r
H
1
+?
r
H
2
+...
3
7. Spontaneity
Entrop y (S )
Measure of disorder/r andomness.
?S =
q rev
T
(reversible process)
T otal Entrop y: ?S
total
=?S
sys
+?S
surr
>0 (spontaneous)
Gibbs Energy (G )
G=H -TS
?G=?H -T?S
Spontaneity:
• ?G<0 : Spontaneous
• ?G>0 : Non-spontaneous
• ?G=0 : Equilibrium
Effect of T emper ature on Spontaneity
?
r
H
?
?
r
S
?
?
r
G
?
Spontaneity
– + – Spontaneous at allT
– – – (lowT ) Spontaneous at lowT
+ + – ( highT ) Spontaneous at highT
+ – + Non-spontaneous at allT
8. Gibbs Energy and Equilibrium
?
r
G
?
= -RT lnK
?
r
G
?
= -2.303RT logK
9. Second Law of Thermodynamics
F or a spontaneous process in an isolated system,?S >0 .
10. Third Law of Thermodynamics
Entrop y of a pure crystalline substance is zero at absolute zero (0 K).
4