thy Indy thermodyne

Energy is consumed to break bonds

Energy is released bonds are
formed
feasibility of a reaction changes involved during
the reaction will equilibrium be achieved or not
 Macfoscopic
dirge Smalllevel
Biglevel

The laws thermodynamics deal with the

of
changes
of macroscopic System
large number ofmolecules

Emplanation
of of matter
properties
Predicts the feasibility of chemical reaction
Predicts the enhent to which a chemical reaction
can occur

Limitations fails to tellus the speedofthereaction

fails to tell the path of reaction
Notapplicable
for microscopic systems
 Terms of Therodynamic
System Asystem in thermodynamics
refers
to that part universe in which
of
observations are made and remaining
universe constitutes the Isurrouncting
Universe System Surrounding

The wall that separates the system

the surroundings is called
from
boundary
The rest of the part of the
Surrounding universe encept system is surrounding

Types_of systems

operetta and matter between

Snchange of energy
woman
It
closedbyster.nlto evelange of matter but enchange
between and surrounding
of energy system
does occur

Isolatedbyster No enchange of energy or matter

between the
system and the surrounding
occurs
tdfibatic.no

state is the condition of a system

Stablofasyten
as specified by its physicalproperties
Pressure Volume temperature composition etc are

called as state variable on statefunction

Stakefuche variables like P V T are called

state functions because their
values depend only on the state of the system
and not on how it is achieved
Depends on initial and state
final
eg P V T density AH AU AG AS
Pathfunctions Aurelius that depend on the path
taken to reach that specific value

eg work done heat transfer

Entensiveproperti.es_ Anenhensive property is a property

whose value depends on the

quantity on site matter present in the system
of
mass volume
Gibbsfreeenergy enthalpy
eg
internal energy heat capacity etc

Hensiveroptics Those properties which do not

depend on the quantity or
size
matter present are known as intensive properties
of
eg Temp pressure surfacetension vapourpressures
Mip Bp and ele

Thetotal
Intercergy energy contained by a system
is called internal energy
The sum
of the energies K E translational vibrational
rotational P E
Absolute internalenergy value cannot be calculated
we can calculate the change in internal energy
 It is an enhensive property
It may change when Matter entersor leavesthesystem
heatpasses into or out the system
of
work done on on by the system
is released by the system Au is
If energy
ve

If energy is
absorbed
by the system AU is tve

Heatcapacity Amount of heat reqd.to raise the

temp of a given mass by unit degree
g CAT
heat capacity

S
watcapac.ly quantity of heat reqd.to
raise the temp
of one
unit mass one degree celsius
by

Thermodynamicprocessed operations or sequential steps

that bring about a change in
a system is called thermodynamic processes

9sothermalprocess ent.rsprocess is carried out

at constant temperature
T constant IT 0 AT 0
 Isobarisprocess The thermodynamic processoccurring
at constantpressure is called
isobaris process P constant IP 0

Isochoricprocess The thermodynamics process occurring

at constant volume is called
isochoric process V 0 du 0

Adiabatifrocess the thermodynamicprocess in

which heat exchange between

system and surrounding is not possible

dg 0

cyclicproces.ae thermodynamic process having

same initial andfinal stake is called
cyclic process system undergoes a number of
different processes and finally returns to theinitialstate

polytropiep rocess.fr ntd

 staticandirreversibleprocer
Reversibleequasi

A processwhich is carried out so slowly that the

system and the surroundings are nearly in equilibrium

is known as Reversible process gradual changeoccurs
quasistatics means that the system seems to be
static but actually it is not
condition doesnot hold good
If the's we call it
irreversible process
All the natural processes are irreversibleprocesses

Spontaneousprocest A reaction thatproceeds on

its own without external help
any

Adiabatic wok_ Wad the positive

sign indicates
Wad is tre when the work is done on
the system
work is done the system it will be
If by
ve

give
a
ralevergychangeyeat lt
internalenergy changes when work is done
the system heat passes in or out
on or by of thesystem
An q q is the heat transferred
due to difference in energy

sft h Éff hfhq.eu

É

Fermodyndofthl the
an isolated system is constant
energy of
law conservation
of of energy

i kearsig4fm
the system
internal energy

of
pressure volume work pressure volume work
done is work done by
expansion
of gas
volume change AV IAN Vf Vp
 ange 8
P
f E
force on piston PXA Pen A
W'is the work done on the system
bymoving
piston
W F x Pen Are
Pen
ve

l Pen AV

II compression

expansion twPAI empansion

singlestepusgradu
alchang we
EPA. PendV
N
I
Reversibleproce gradual change
Irreversible process single step
When

Y
1 Pen du

f R dP Iv Pdu dp

Pdv

Ideal gasegn P
MRI
du
Wrer ARI

ft
MRT du

NRT flav
NRT In v2 lay

µ
NRT

2.303 n RT log
V21

Fg
15St novemberpata
xttsihtrs.ba
path

Takes infinitetime Takesfinitetime

f

gmagingprocess natural prom

Systemis alwaysin Equilibriums enists
equilibrium only at the beginning y
and at the end

workobtained is workobtained is not

aaonei.net pga Pen

PenGA w
o W
O

7romtstlace A.ie qtw

AU q
For isothermal change 14 0

1st lack for isothermal reversible and irreversible

changes
 For isothermal change AU 0
For isothermal irreversible change
W
q Perly Vi
For isothermal reversible
change

9 w ART in 2.303nAlog

For adiabatic change 9 0

IAUadT
 Summary of basic definitions
● Thermodynamics is the study of heat (thermo) and work (dynamics)..
● System : System is part of the universe which is arbitrarily set off from the rest of the
universe by definite boundaries for the purpose of experimental or theoretical
studies.
● Surrounding : The remainder of the universe is the surroundings of the system.
● Intensive Properties do not depend on the amount of matter present in system.
Examples: Pressure, Temperature, Density, M.P, B.P. etc.
● Extensive Properties depend on the amount of matter present in the system.
● Examples: Mass, Volume, Heat Capacity, Enthalpy, Entropy. Etc.
● State Functions: Property of system depends only on the state of the system
● Examples: Enthalpy, Entropy, Internal Energy, Free Energy, etc.
● Path Functions: Property of system depends only on the path by which process is
done. Examples: work and heat
 Summary of basic definitions
Thermodynamic Processes

Isothermal Isobaric Isochoric Adiabatic Cyclic

temperature pressure volume system

A process
remains remains remains cannot
when initial
constant constant constant exchange
and final state
throughout throughout throughout heat with
of the system
the process the process the process surrounding
is same.
i.e., : dT = 0 i.e., : dP = 0 i.e., : dV = 0 i.e., : dq = 0
 Which of the following are state functions?
(I) q + w
AU (II) q (III) w (IV) H - TS
AY

A. (I) and (IV)

Mpathfution
B. (II), (III) and (IV)

C. (I), (II) and (III)

D. (II) and (III)

 Which of the following are state functions?
(I) q + w (II) q (III) w (IV) H - TS

A. (I) and (IV)

B. (II), (III) and (IV)

C. (I), (II) and (III)

D. (II) and (III)

 Internal Energy (U or E)

● Internal energy is the energy contained within the

thermodynamic system.

● Internal energy is the sum of various energies like kinetic energy

(translational, rotational, vibrational), potential energy,
electronic energy, nuclear energy, etc.

● Absolute value of internal energy can not be determined

ΔU = Q + W

● It is an extensive property
 Types of processes
Reversible process Irreversible process
A process which is carried out so slowly Process other than reversible
that the system and surrounding are processes are known as irreversible
always in equilibrium during this process process

Sand

Pext = Pint ± dP
This process is very slow and This process complete in finite time
takes infinite time The system is far away from state of
Throughout the process, the system remain equilibrium
infinitesimally closer to state of equilibrium
 Types of processes
Expression ΔU= ΔH =
Process Expression for q Work on PV-graph
For w nCV∆T nCp∆T

Reversible
isothermal w = –nRT ln V2 q = nRT ln V2 0 0 P1
process V1 V1
P1 P1

P(at
= –nRT ln q = nRT ln P2

m)
P2 P2 V1 V2
Irreversible Volume
isothermal w = –Pext (V2–V1) q = Pext (V2–V1) 0 0 P1
process
P2
nRT nRT

P(at
= –Pext

m)
P2 P1
V1 V2
Isobaric w = –Pext (V2–V1) q = ∆H = nCP∆T nCV∆T nCP∆T Volume
process
= - nR∆T

P(at
m)
V2 V1
Volume
 Types of processes
Expression ΔU = ΔH =
Process Expression for q Work on PV-graph
For w nCV∆T nCp∆T

Isochoric w=0 q = ∆U = nCV∆T nCV∆T nCP∆T P2

process
P1

P(at
m)
Volume

Reversible w = nCV(T2–T1) q=0 nCV∆T nCP∆T P1

adiabatic PVγ = constant Isotherm
process TVγ–1 = constant P2 Adiabatic

P(at
P2V2–P1V1

m)
= TP1–γ/γ = constant
γ–1
V1 V2
Volume

Irreversible w = nCV(T’2–T’1) P1 Rev

adiabatic Isotherm
process P2 Rev

P(at
P2V2–P1V1

m)
= Adiabatic
γ–1
V1 V2’ V2
Volume
10 mole of ideal gas expand isothermally and reversibly from a pressure of 10 atm to 1
atm at 300 K. What is the largest mass which can be lifted through a height of 100
meter?

W in isothermally reversibly
W 2.303ART P P mgh
log
2 303 8.3 30 403 Mx 103

ME 57.34 kg 51kg
 First law of thermodynamics
Law of energy conservation
★ This law states that energy cannot be created or destroyed only gets
converted from one form to another form.
● Mathematical form of 1 st Law of thermodynamics :
U2 = U1 + q + W
so ΔU = (U2 - U1) = q + W
U1 = internal energy at initial state
U2 = internal energy at final state
q = amount of heat is given to it
W = amount of work is done on it
 Sign convention of work and heat
q Heat is absorbed by the
positive system from the surroundings

W W
System
Positive negative
Work is done on the Work is done by the
system system (Expansion)
(Compression)
Negative
q
Heat is given by the system to the
surroundings
 Which of the following is a state function and also an extensive property?

A. Internal energy

B. Pressure

C. Molar heat capacity

D. Temperature
 Which of the following is a state function and also an extensive property?

A. Internal energy

B. Pressure

C. Molar heat capacity

D. Temperature
Out of molar entropy (I), SPecific volume (ii), heat capacity (iii), volume (iv) extensive
properties are:

A. I, II

B. I, II, IV

C. II, III

D. III, IV
Out of molar entropy (I), SPecific volume (ii), heat capacity (iii), volume (iv) extensive
properties are:

A. I, II

B. I, II, IV

C. II, III

D. III, IV
 Which of the following quantities is not a state function?

A. temperature

B. Entropy

C. Enthalpy

D. Work
 Which of the following quantities is not a state function?

A. temperature

B. Entropy

C. Enthalpy

D. Work
Warming ammonium chloride with Sodium hydroxide in a test tube is an example of

A. Closed system

B. Isolated system

C. Open system

D. None of these
Warming ammonium chloride with Sodium hydroxide in a test tube is an example of

A. Closed system

B. Isolated system

C. Open system

D. None of these
Which of the following changes would definitely increase the internal energy of a
system?

A. The system gains heat and perform work

B. The system gains heat and has work performed on it.

C. The system loses heat and performs work.

D. The system loses heat and has work performed on it.

Which of the following changes would definitely increase the internal energy of a
system?

A. The system gains heat and perform work

B. The system gains heat and has work performed on it.

C. The system loses heat and performs work.

D. The system loses heat and has work performed on it.

A system absorbs 10Kj of heat at constant volume and its temperature rises from 27oC
to 37oC. The value of 𝝙U is

A. 1000kj
At constant volume heat
change internalenergy
B. 10Kj change
AU 10kg
C. 0 q
D. 1Kj
A system absorbs 10Kj of heat at constant volume and its temperature rises from 27oC
to 37oC. The value of 𝝙U is

A. 1000kj

B. 10Kj

C. 0

D. 1Kj
For a particular process q=-10Kj and W=25Kj. Which of the following statements is
true?

AU w
A. Heat flows from the surrounding to the system.
q
10 25
B. The system does work on the surrounding. 1545
C. 𝝙E= -35KJ

D. None of the above is true

For a particular process q=-10Kj and W=25Kj. Which of the following statements is
true?

A. Heat flows from the surrounding to the system.

B. The system does work on the surrounding.

C. 𝝙E= -35KJ

D. None of the above is true

 An ideal gas at constant temperature and pressure expands, then its

A. Internal energy remains same

B. Internal energy decreases

C. Internal energy increases

D. Entropy first increases and then decreases

 An ideal gas at constant temperature and pressure expands, then its

A. Internal energy remains same

B. Internal energy decreases

C. Internal energy increases

D. Entropy first increases and then decreases

 Level - 3 JEE ADV 2001

In thermodynamics, a process is called reversible when

A. Surroundings and system change into each other

B. There is no boundary between system and surroundings

C. The surroundings are always in equilibrium with the system

D. The system changes into the surroundings spontaneously.

 Level - 3 JEE ADV 2001

In thermodynamics, a process is called reversible when

A. Surroundings and system change into each other

B. There is no boundary between system and surroundings

C. The surroundings are always in equilibrium with the system

D. The system changes into the surroundings spontaneously.

 Level - 3 JEE ADV 2001

Which of the following statements is false?

A. Work is a state function

pathfunction
B. Temperature is a state function

C. Changes in the state is completely defined when the initial

and final states are specified.

D. Work appears at the boundary of the system.

 Level - 3 JEE ADV 2001

Which of the following statements is false?

A. Work is a state function

B. Temperature is a state function

C. Changes in the state is completely defined when the initial

and final states are specified.

D. Work appears at the boundary of the system.

 Therdynamic depiction of idealgas

If internal energy is directly proportional to its absolute

temperature then it is an ideal gas

1 1 1 1
Thermodynamic equilibrium
At thermodynamic equilibrium there is no change
in properties
of system with time it satifies
the three equilibriums
Mechanicalequilibrium There is no mechanical
motion and the pressure and the volume
of
the system are not changing

Thermalequilibrium here.is no
flow of heat
and the temp and the
system does not change
 chemical
reaction
chemicequibben If any
is takingplace in the
system then the rate of forward reaction
isequal to the rate backward reaction
of
which means that the overall moles the system
of
is constant

Inthawofthermodynamics

Two systems in thermal equilibrium with a third

bystem are also in thermal equilibrium with
each other in

SEMI vimeo.im
IBIFadI
equilibrium

Werk drinvarietypofardynamic
Adiabaticffday o w an
q tr
TV r constant P constant
PVE constant
 An her AT
Rky nff
Isochoricprocess dv.co
W O
AU
MG AT q

Isobaricprocess.de O
W PAV MRAT
AH ACp AT

Enthalpy Most the chemical reaction takesplace

of
in open air that is at constant pressure

AU
PAV
qp

U2 U qp P V2 Vi

Ip U2 U PV2 PV
9p PR
H
µ PV
UtPD
IH
Up H2
19p
 AUthRAI
ve
HAITI
enothermic process
IAH

heat is released by
the system
ve endothermicprocess heat is absorbed
bythe system

End
The difference between AA and AU is not
so significant the system consists
if of only
solids and or liquids
It becomes significant when we have gases

AH AU PAV
there isn't
if any significant
change in the volume
then AV O
whichmeans PAV D
AH AU
Enthalpy gases
Ideal PVA MART
gases
PUB MBRT
P VB VA MB n A RT

CsAD
1q
specific heat capacity

dm
reeationm.I.fm Q ff
At const v AU
q
Af cons P AH
qp
AH AU PAV
Gp Eu DAV
Imol ideal
gas PAV RAT
RIT.CC
qpi q
heat capacity q CAT
Cp AT
Gp

CPAT CVAT RAT

CpAA AT R
 ÉevRI
Typesofprocesse graphs

Isothermal_ AT D Pen
Pfaff

It ll
Isobaric AP O

in
pf

Isochore AV O

KE
cyclic

Eff 7

I
Adiabatic
Emthear heat capacity em
If
Cs ors Specific heat capacity Cs
FIT
Cp at const pressure Cp
type
Cpm Molar heat capacity at coast

pressure
14

Cps Specific heat capacity at const

pressure
1

Cv heat capacity at constvolume

9
Crm Molar heat capacity atconst volume
Iff
Cvs specific heat capacity at const volume
Iff
 mydriatic II
heat capacity C or Cy is a path function

heat capacity may vary from α to α depending

on the process
Isothermal C α

Isobaric C Cp
980choric C Cu
Adiabatic q D C 0

freedoms The total number modes

Degree
of of on
which
of an ideal
a molecule

gas can enchange energy during collisions

Modes
of
movement translational Rotational
vibrational

7
17 4 Poisson's ratio

It
Dot
 f Cp Cv R Cr
fI2 4
37 04 3 3
gasmonoatomic
51
Diatomic 31 22 5 T
gas
71
Triatomic 3R 6 YR 3R
nonlinear

37 212
Triatomic
linear
5
F By 75

Law
ojquipartitionofengy
Energy equal to is associated with each
IKT
degree of freedom per ideal gas molecule

U molecule
KTff
wee
4 ktxn.at
RT
you f
foramy U Rx Txfxn
f
 AUIAHMeasurement

Adevi.ee called calorimeter is used

I at const volume qu
in at court pressure Gp

Reactionnthalpy The enthalpy change accompanying

a reaction is called reaction

enthalpy
It the heat content of the system
is

It decides whether a reaction will happen or not

Reactants Products
An H Sum all the enthalpies products
of of
sum all the reactants
of enthalpies
of
a
products Ebi Hreactant

of the balanced
ai bi Stoichiometric coefficients
reactions

at bB cc dD
ArH felt c dH D aH A bH B
 A
Standardanthalpyfreaction

Enthalpy change for a reaction when all the

participating substances are in their standard
states
Ipureform K1baI
Idurigphasetoransformatios
Standard enthalpy
of fusion
lice weaker

standard enthalpy vaporization

of
water water vapour
Standard enthalpy Sublimation
of
Solid
vapor

Sandenthalpyof fusion Enthalpy change that

accompanies melting
of one mole of a solid substance in a standard
state
Apus 4 Endothermic process
 Amount heat
Sudardenthalpofrapolitain of
regd to vaporize
on mole
of a liquid at standard state
Endothermic
Avap H process

standardenthalpyfsubbmation change in enthalpy

when one mole solid substance sublimes
of a

at a standard stake
Altsub Endothermicprocess

standardenthalpy fformation Enthalpy change for

the formation of one
mole from its elements their
of a compound in

reference stake
Af H is also standard molar
enthalpyofformation
The chemicalequations
A balanced chemical equation together with the value
AMH
of
balanced thermochemical equation
Coefficients in a

refer to the number of moles not molecules

Numerical Art refers to the number of
of
moles
of substance unit 125 mod 1

Needforsecondlace
spontane.us The reactions proceedon its own
proof

andspotaeit i.EE

AS
EntropyI guy
Thetotal entropy change AS
for the system and
the surrounding
for a spontaneous process
 AStotal AS Assure 70
system

ho
chargeinthermodynepcoest
AS never men
E
7orisot hermal.AE arm

AS
torches never
f
cure AS ncp in

For
Adiabatic As 0
grer a

Second
lawofthermodynamics

The entropy an isolated system universe

of
tends to increase
AStotal AS Assure 70
system
G
7yergyande.ly
H TS
9
AH Gibbs helmholtzeqn

If AG is ve the process is going to

be spontaneous
AG CO AH TAS CO
AH C TAS

If AG is tre the process is non

A 970
spontaneous
AH TAS 70
AH TAS

ftp
at low
temp
f
ÉÉ É TÉLÉS
at high temp
Ideacreofthermodynamics

The absolute entropy a perfect

crystaline substance
of
at absolute zero temperature is zero

vaceofonstantheats
a ummati. l
reaction takes place in several steps
then its standard reaction enthalpy is

of standard
sum all the
enthalpies of
intermediate reactions

Bjy.ie gyH enthalpy offormation

Nacl 5 Nat Cl
lg g Acattice

Natly ee g Nacl 5 Alattice

Nals Nall s
I 112 g Af
 Nacs 4297 HE
91
e Nace
Adiss
Sh

Nalg fattice

Hees lace AsubH Ai

Aflt Ache AegH

Alatticell

The enthalpy
frehoffequation of any process
Whether physical or chemical

varies with the temperature

Attraction products reactants

1 75 Eye foggy
G product P reactant
Acp Sum
If of heat capacitiesofproducts
sum heat capacities reactants
of of
 III
genegychangeandequir.vn
0 AnG RT link
AMG RT link
An 4 2.303 Rt log K
we also know that

Ang AnH TAS RT Mls

 Enthalpy (H)
● When a process takes place at constant pressure, the heat
absorbed or released is equal to the Enthalpy change.
● Absolute value of internal energy can not be determined
● The change in enthalpy (ΔH) is measured, which is the heat
added or lost by the system.
● Enthalpy is the sum of the system's internal energy and the
product of its pressure and volume.
H = U + pV
ΔH = ΔU + Δ(pV), {pV = ngRT}
ΔH = ΔU + Δ(ngRT) ng = no. of gaseous moles
● It is an extensive property
 Heat capacity
● Heat capacity or thermal capacity is a physical property of matter,
defined as the amount of heat to be supplied to an object to produce a
unit change in its temperature.Heat required to raise the temperature of
system by 1oC under the given process is known as total heat capacity.

Δq dq
Mathematically CT = = (unit: J/oC)
ΔT dT

● Since heat capacity is a path function. For an ideal gas, two different types of
molar heat capacities are defined:
● Molar heat capacity at constant volume (CV)
● Molar heat capacity at constant pressure(Cp)
CV = Cp – R or Cp = Cv + R
 Adiabatic Process and Poison’s ratio
For an adiabatic reversible process :

P T V𝜸–1 = constant
2 PV𝜸 =constant

PV𝛾 = C 1
V
Poison’s Ratio
It is the ratio of molar heat capacity at constant pressure and molar heat
capacity at constant volume. CP
γ=
CV
A gas is allowed to expand in a well insulated container against a constant external
pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The
change in internal energy ΔU of the gas in joules will be:-

A. – 500J

B. – 505J

C. + 505J

D. 1136.25J
A gas is allowed to expand in a well insulated container against a constant external
pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The
change in internal energy ΔU of the gas in joules will be:-

A. – 500J

B. – 505J

C. + 505J

D. 1136.25J
Gas in a container absorbs 300 J of heat. After this, 100 J of work is done on it which is
followed by 50 J of work done by the gas. The increase in the internal energy of the gas
is:

A. 450 J

B. 400 J

C. 350 J

D. 200 J
Gas in a container absorbs 300 J of heat. After this, 100 J of work is done on it which is
followed by 50 J of work done by the gas. The increase in the internal energy of the gas
is:

A. 450 J

B. 400 J

C. 350 J

D. 200 J
 Second law of thermodynamics

I. No cyclic engine is possible which take heat from one single source
and in a cycle completely convert it into work without producing any
change in surrounding.
II. In an irreversible process, entropy of universe increases but it
remains constant in a reversible process
ΔSsys + ΔSsurr = 0 for rev. Process

ΔSsys + ΔSsurr > 0 for irrev. Process

ΔSsys + ΔSsurr > 0 (In general)

 Entropy
The second law of thermodynamics predicts direction of natural change. It do so with the
help of state function ‘S’ - called entropy of system. But for predicting direction of natural
change another quantity Ssurrounding is also needed ,which is called entropy of surrounding

dq
dSsystem = dqrev dSsurr = –
T
T

ΔSsystem ΔSsurrounding
Reversible B dqrev B dqrev Note that
process ∫A T
– ∫A
T
Irreversible B dqrev B dqrev
process
∫A T
– =–∫A T A→B

General Expression, for any process :

 Gibbs free energy and Enthalpy
● Gibbs free energy is a quantity that is used to measure the maximum work done in
a thermodynamic system when the temperature and pressure are kept constant
Mathematically

G = H - TS

Gibbs - Helmholtz equation

ΔG = ΔH - TΔS

● Enthalpy:
It is the sum of the internal energy(U) and the product of pressure (P)
and volume (V) H = U + PV

or ΔH = ΔU + PΔV (at constant pressure) or ΔH = ΔU + nRΔT

or ΔH = qP
 Condition for the process to be
spontaneous

ΔG = ΔH - T ΔS

ΔH T ΔS Conditions ΔG
-ve (favourable) +ve (favourable) (any) -ve spontaneous
-ve (favourable) -ve |ΔH| > (TΔS) -ve spontaneous
(unfavourable)
+ve +ve (favourable) |TΔS| > |ΔH| -ve spontaneous
(unfavourable)

ΔG = (-ve) Spontaneous
ΔG = (+ve) Non spontaneous
ΔG = 0 Equilibrium
 For the reaction, 2Cl(g) ⟶ Cl2(g), the correct option is

CO
AS
A. ∆rH > 0 and ∆rS > 0 AMH CO
B. ∆rH > 0 and ∆rS < 0

C. ∆rH < 0 and ∆rS > 0

D. ∆rH < 0 and ∆rS < 0

 For the reaction, 2Cl(g) ⟶ Cl2(g), the correct option is

A. ∆rH > 0 and ∆rS > 0

B. ∆rH > 0 and ∆rS < 0

C. ∆rH < 0 and ∆rS > 0

D. ∆rH < 0 and ∆rS < 0

For a given reaction, ∆H= 35.5 kJ mol–1 and ∆S = 83.6 J K-1 mol-1. The reaction is
spontaneous at (Assume that ∆H and ∆S do not vary with temperature).

A. T > 425 K

B. All temperatures

C. T > 298 K

D. T < 425 K
For a given reaction, ∆H= 35.5 kJ mol–1 and ∆S = 83.6 J K-1 mol-1. The reaction is
spontaneous at (Assume that ∆H and ∆S do not vary with temperature).

A. T > 425 K

B. All temperatures

C. T > 298 K

D. T < 425 K
 Third law of thermodynamics

● The entropy of a perfectly crystalline solids may be taken as zero at

the absolute zero of temperature
● It helps in calculation of the absolute entropy of a substance at any
temperature T
● Let S0 = entropy at 0 K , S = entropy at T K
T CpdT
ΔS – S – S0 = ∫0 T
0 at 0 K by third law of thermodynamics
T CpdT
S= ∫0 T
 Third law of thermodynamics
★ For chemical reaction
aA + bB – cC + dD
ΔS° system= (𝚺nrS°m)products = (𝚺n1S°m)reactant

Where S0 = standard molar entropy. It can calculated using third law of

m
thermodynamics.
–Qsystem –ΔHsystem
ΔS° surr = T = T

For a perfectly crystalline substance at 0 K, entropy = 0

● For phase transformations

ΔHfus ΔUfusion
(for constant P) (for constant V)
ΔSfus = T ΔSfus = T
ΔHvap ΔUvap
ΔSvap = (for constant P) ΔSvap = (for constant V)
T T
 When one mole of an ideal gas is compressed to half of its initial volume and
simultaneously heated to twice its initial temperature, the change in entropy of gas
(ΔS) is:

A. Cp,m ln2

B. Cv,m ln2

C. R ln2

D. (Cv,m – R)ln2
 When one mole of an ideal gas is compressed to half of its initial volume and
simultaneously heated to twice its initial temperature, the change in entropy of gas
(ΔS) is:

A. Cp,m ln2

B. Cv,m ln2

C. R ln2

D. (Cv,m – R)ln2
 Relationship between ΔH and ΔU
We know that,
H = U + PV
dH = dU + d(PV)

Case - 2: If volume is constant

Case - 1: If pressure is constant
dH = dU + VdP
dH = dU + PdV
or ΔH = ΔU + VΔP
or ΔH = ΔU + PΔV
 Enthalpy change of a reaction
● Amount of heat lost or gained in the chemical reactions, when all the
reactants and products are maintained at same temperature and
pressure
● ΔrH = (sum of enthalpies of products) - (sum of enthalpy of reactants)
ΔrH = ∑ (vΔH)products - ∑(vΔH)reactants
Where v is the stoichiometric coefficients of reactants and products,
respectively.
● Standard Enthalpy of Reaction:
The enthalpy change accompanying the reaction when all the reactants
and products are taken in their standard state.
 Enthalpy of reactions/ Processes
Enthalpy of neutralisation : The amount of heat released when one gram
equivalent of an acid is neutralised by one gram equivalent of a base

Enthalpy of formation : The amount of heat absorbed or evolved when 1 mole

of the substance is directly obtained from its constituent elements

Enthalpy of combustion : It is the enthalpy change when one mole of the

substance undergo complete combustion to give combustion products.

Bond enthalpy : Heat change during formation or breaking of one mole bond
 Bond energies of few bonds are given below:
Cl ─ Cl = 242.8 kJ mol–1, H ─ Cl = 431.8 kJ mol–1
O ─ H = 464 kJ mol–1, O = O = 442 kJ mol–1
Using the B.E., calculate ΔH for the following reaction,
2Cl2 + 2H2O ⟶ 4HCl + O2

A. 906 kJ mol–1

B. 172.4 kJ mol–1

C. 198.8 kJ mol–1

D. 442 kJ mol–1
 Bond energies of few bonds are given below:
Cl ─ Cl = 242.8 kJ mol–1, H ─ Cl = 431.8 kJ mol–1
O ─ H = 464 kJ mol–1, O = O = 442 kJ mol–1
Using the B.E., calculate ΔH for the following reaction,
2Cl2 + 2H2O ⟶ 4HCl + O2

A. 906 kJ mol–1

B. 172.4 kJ mol–1

C. 198.8 kJ mol–1

D. 442 kJ mol–1
 Hess law of constant heat summation
if a chemical reaction can be made to take place in a number of ways in one
or in several steps, the total enthalpy change is always the same i.e it is
independent of intermediate steps involved in the change
>
Q

A D
q3
q1 >
B q2 > C
Let q1 + q2 + q3 = Q’ joule
According to Hess’s law we must have Q = Q’
 Consider the following processes
ΔH(kJ/mol)
1/2 A ⟶ B +150
3B ⟶ 2C + D -125
E + A ⟶ 2D +350
For B + D ⟶ E + 2C, ΔH will be:

A. 525 kJ/mol

B. -175 kJ/mol

C. -325 kJ/mol

D. 325 kJ/mol
 Consider the following processes
ΔH(kJ/mol)
1/2 A ⟶ B +150
3B ⟶ 2C + D -125
E + A ⟶ 2D +350
For B + D ⟶ E + 2C, ΔH will be:

A. 525 kJ/mol

B. -175 kJ/mol

C. -325 kJ/mol

D. 325 kJ/mol
 Entropy & Gibbs free energy of
reaction
Entropy of reaction:

The difference between the sum of the entropies of the products and
the sum of the entropies of the reactants:

ΔrS = ∑ Sproducts - ∑ Sreactants

Gibbs free energy of reaction:
The difference between the sum of the Gibbs free energies of the
products and the sum of the Gibbs free energies of the reactants.

ΔrG = ∑ ΔGf,products - ∑ ΔGf,reactants

ΔG = ΔH - TΔS
 [JEE Main 2019]

The entropy change associated with the conversion of 1 kg of ice at 273 K to water
vapours at 383 K is: (Specific heat of water liquid and water vapour are 4.2 kJ K–1 kg–1
and 2.0 kJ K–1 kg–1; heat of liquid fusion and vaporization of water are 334 kJ kg–1 and
2491 kJ kg–1, respectively).
(log 273 = 2.436, log 373 = 2.572, log 383 = 2.583)

A. 7.90 kJ kg–1 K–1

B. 2.64 kJ kg–1 K–1

C. 8.49 kJ kg–1 K–1

D. 9.26 kJ kg–1 K–1

 [JEE Main 2019]

The entropy change associated with the conversion of 1 kg of ice at 273 K to water
vapours at 383 K is: (Specific heat of water liquid and water vapour are 4.2 kJ K–1 kg–1
and 2.0 kJ K–1 kg–1; heat of liquid fusion and vaporization of water are 334 kJ kg–1 and
2491 kJ kg–1, respectively).
(log 273 = 2.436, log 373 = 2.572, log 383 = 2.583)

A. 7.90 kJ kg–1 K–1

B. 2.64 kJ kg–1 K–1

C. 8.49 kJ kg–1 K–1

D. 9.26 kJ kg–1 K–1

 JEE Mains _2023

For independent process at 300 K

Process ΔH/kJ mol-1 ΔS/j K-1

A -25 -80

B -22 40

C 25 -50

D 22 20

The number of non-spontaneous process from the following is _______.

 JEE Mains _2023

For independent process at 300 K

Process ΔH/kJ mol-1 ΔS/j K-1

A -25 -80

B -22 40

C 25 -50

D 22 20

The number of non-spontaneous process from the following is _______.

Ans: 2
 JEE Mains _2023

One mole of an ideal monatomic gas is subjected to changes as shown in the graph.
The magnitude of the work done (by the system or on the system) is _______ J
(nearest integer)

Given: log 2 = 0.3, ln 10 = 2.3

 JEE Mains _2023

One mole of an ideal monatomic gas is subjected to changes as shown in the graph.
The magnitude of the work done (by the system or on the system) is _______ J
(nearest integer)

Given: log 2 = 0.3, ln 10 = 2.3

Ans: 620
 JEE Mains _2023

28.0 L of CO2 is produced on complete combustion of 16.8 L gaseous mixture of ethene

and methane at 25ºC and 1 atm. Heat evolved during the combustion process is __ kJ.
Given: ∆ HC (CH4) = –900 kJ mol–1
∆HC (C2H4) = –1400 kJ mol–1
 JEE Mains _2023

28.0 L of CO2 is produced on complete combustion of 16.8 L gaseous mixture of ethene

and methane at 25ºC and 1 atm. Heat evolved during the combustion process is __ kJ.
Given: ∆ HC (CH4) = –900 kJ mol–1
∆HC (C2H4) = –1400 kJ mol–1
 JEE Mains _2023

28.0 L of CO2 is produced on complete combustion of 16.8 L gaseous mixture of ethene

and methane at 25ºC and 1 atm. Heat evolved during the combustion process is __ kJ.
Given: ∆ HC (CH4) = –900 kJ mol–1
∆HC (C2H4) = –1400 kJ mol–1

Ans: 847
 JEE Mains _2023

Which of the following relations are correct?

(A) ΔU = q + pΔV
(B) ΔG = ΔH - TΔS
(C) ΔS = qrev/T
(D) ΔH = ΔU - ΔnRT
Choose the most appropriate answer from the options given below:

A. C and D only

B. B and C only

C. A and B only

D. B and D only
 JEE Mains _2023

Which of the following relations are correct?

(A) ΔU = q + pΔV
(B) ΔG = ΔH - TΔS
(C) ΔS = qrev/T
(D) ΔH = ΔU - ΔnRT
Choose the most appropriate answer from the options given below:

A. C and D only

B. B and C only

C. A and B only

D. B and D only
 JEE ADV_2019-P2
Chemicalkinetic
JEE ADV_2019-P2

Answer (2.3)