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N.Saravanan, AP/Chemistry, Mahalakshmi EngineeringCollege,Trichy-622!.

MAHALAKSHMIENGINEERING COLLEGE

TIRUCHIRAPALLI - 621 213

Pre"are# $y%

N.Saravanan.,AP/Chemistry.

Sub. Code: CY 6151 Semester : I

Subject : !"I!RI!" CH#ISTRY-I &nit '((% C)EM(CA* T)E+MNAM(CS

2 # $ r%s & u e s t' o ( s $(d A ( s ) ers

*1. +e,'(e te terms Sstem / Surrou(d'(0s $(d ou(d$r.

S y s t e m: The Part of the universe. S ur r o u n din g s:

Remaining part of the universe. B o u n d ar y:

Separating the system and surroundings.

*2. $t $re te tes o, sstems4

Isolated system, closed system, opens system.

*3. $t do ou me$( b $( 'so$ted sstem/ cosed sstem $(d oe( sstem4

I so lated s y s t e m: which cannot exchange oth energy and matter! "x: universe.

#los e d s y s te m: only heat exchange

$ p e n s y s t e m : only mass exchange.

*. $t do ou me$( b $ st$te o, $ sstem4

"xchange ta%es place at oundary etween system and surroundings.

State: that condition in which all variales are fixed and unvarying.

*5. +e,'(e te 'soterm$/ $d'$b$t'c / 'sob$r'c/ 'socor'c c$(0e.

I soth e rm al ch a n g e : one at constant temperature. dT&'

( d ia atic cha n g e: )o heat is exchanged into or out of a system i.e, insulated.

I so aric ch a n g e: one at constant pressure. dP&'

I soc h oric ch a n g e : one at constant volume. d*&'

*6. St$te d',,ere(t ,orm o, de,'('t'o(s o, seco(d $) o, termod($m'cs.

+or% can always e converted into heat, ut heat cannot e completely converted into wor% ,

only a fraction of heat can e converted into wor% and the rest remains unavailale andunconverted.

Clausius statement: It is impossile to construct a machine, which can transfer heat from a cold

ody to a hot ody, unless some external wor% is done on the machine.

Kelvin statement: It is impossile to ta%e heat from a hot ody and convert it completely into wor%

y a cyclic process without transferring a part of heat to a cold ody.

*7. +e,'(e te st$teme(t o, (tro. "'8e 'ts m$tem$t'c$ e9ress'o(.

It is a measure of degree of disorder or randomness in a molecular system

"x: solidliuid, entropy increases. -iuidsolid, entropy decreases.

S & q r e v

T

rev & heat change and T& Temperature.

*. $t $re te roert'es o, $ sstem4

Two properties. /. Intensive properties 0. "xtensive properties.

/. I ntens iv e p r o p e rtie s: 1epends on only the nature of the sustance present a system.

"x:Temperature , Pressure, #oncentration.

0. " x t e n s iv e p r o p e rtie s : 1epends on the amount of the sustance present a system.

"x:2ass, *olume, ", S, 3.

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*;. +e,'(e c$us'us '(et o,, 'soterm.

Pc

Pd

G =RT l#KeqRT l#C D

A B

15. +er'8e te m$tem$t'c$ ,orm o, 8$(>t o,, e

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S P S V ;iii. V T= T V

;iv. P T= T P

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*1. 9$'( te term'(oo0 '( termod($m'cs.

S y s t e m: The Part of the universe. S ur r o u n din g s:

Remaining part of the universe. B o u n d ar y:

Separating the system and surroundings.

T y p e s o f s y s t ems

Isolated system, closed system, opens system.

I so lated s y s t e m: which cannot exchange oth energy and matter! "x: universe.

#los e d s y s te m: only heat exchange

$ p e n s y s t e m : only mass exchange.

State of a system: "xchange ta%es place at oundary etween system and surroundings.

State: that condition in which all variales are fixed and unvarying.

I soth e rm al ch a n g e : one at constant temperature. dT&'

( d ia atic cha n g e: )o heat is exchanged into or out of a system i.e, insulated.

I so aric ch a n g e: one at constant pressure. dP&'

I soc h o r ic ch a n g e : one at constant volume. d*&'

*2. 9$'( te e(tro c$(0e ,or $( 'de$ 0$s.

(ccording to I law of thermodynamics d" & 9w 9999999999999 ;/

+here, & heat change and w & wor% done.

In reversile isothermal expansion, there is no change of internal energy d" & '.

"uation ;/ ecomes, rev?w & ' @ rev & w 999999999999999;0The wor% done in an expansion of n moles of a gas from volume */ to *0 at constant

temperature T is given y

+ & nRT l#V

% 99999999999999999999 ;>V&

"uation ;0 ecomes

Vrev & nRT l#

%

V&

9999999999999999;A

ut S &q r e v

T

and rev

& T S

"uation ;A ecomes, T S & nRT l#V%

V&

& V VS &

TnRT l# %

V&

@ S & nR l# %

V&

S & 0.>'> nR lo$V%

V&

9999999999999999999999999;

"uation ; is %nown as an entropy change in an isothermal expansion of an ideal gas.

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*3. 9$'( te e(tro c$(0e ,or $ re8ers'be $(d 'rre8ers'be rocess.

" ntr o p y ch a n g e f or a r e v ersile p r oc e s s :

a #onsider an isothermal and reversile expansion of an ideal gas.

If the system asors amount of heat from the surroundings at temperature T, the

qincrease in entropy of the system is given y S

system=T

qc The heat loose, the entropy of the surroundings decreases Ssurroundings =T

STota

=SSystem

+Ssurroundings

S =q

+

q

Tota

T

T

STota

3

In a reversile isothermal process, there is no net change in entropy.

" ntr o p y ch a n g e f or a irr e v ersile p r oc e ss:

( system maintained at high temperature T/ andIts surroundings maintained high temperature T0.

If amount of heat passes irreversily from the system to surroundings, then

q1ecrease in entropy of the system S

System=T&

qIncrease in entropy of the surroundings S

Surroundings=+T%

)et change in entropy STota

=SSystem

+SSurroundings

=q

+q

T&

&=q

T%

&

T% T& T T

=q

& %

T&T%

Since T/CT0, T/9T0 is positive. 8ence STotal & positive value.

STotalC'

In an irreversile process, the entropy of the system increases.

(ll the spontaneous process are irreversile and entropy of the systemalways increases.

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*. 9$'( te c$us'us '(e

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T

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*5. 9$'( "'bbs @ Hemot= e

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PG (H1* !&"

T P

"n;/' is another form of 3is ? 8elmholt4 euation.

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Significance:

;i. It relates 3 and 8 with temperature at constant pressure.

;ii. It gives the nature of a reaction. 3 value & 9ve, the reaction is spontaneous.

3 value & ', the reaction is in eulirium.

(pplications:

/. #alculate 8 f or t he cell r eact ion: It is calculated as follows.

8 &

n" #

#

T

P

0. # a lcu late the e m f o f a c e ll: It is calculated as follows.

#

= H

+T#

n"

T

P>. #alculation of entropy change: It is calculated as follows. 3 & 8 ? TS

A. It is used to calculate 8 value from free energy change of two different temperatures.

*6. Te ,ree e(er0 c$(0e $ccom$('(0 $ 0'8e( rocess 's -5.77 %Der moe $t 25*C $(d @3.6 %D $t 35

*C. c$cu$te te c$(0e '( e(t$ ,or te rocess $t 3*

*C.

(G )3is ? 8elmholt4 euation is G (H1*

T 3/& 9J.HH %K

30& 9J>.GJ %K 3 & 30 9 3/ & 0.'.

T/ & 0'# & 0E0H> & 0J '# & >E0H> & >'J s re$t'o(s.

+e %now that ,;/. d" & TdS ? Pd*;0. d8 & TdS E *dP;>. d( & 9SdT ? Pd*;A. d3 & 9SdT E *dP

;/. (ccording to internal energy @

The comined form of I and II law is ,d" & TdS ? Pd* 999999999999999999999999999999999999999;/If * is constant then d* & ' , en ;/ ecomes

# =T >!%"

VIf S is constant then dS & ' , en ;/ ecomes

# =P >!'"

S1iff. en ;0 w.r.t * at constant S

%#

SV

T V S

>!5"

1iff. en ;> w.r.t S at constant *

%#V S

P S V

>!3"

#ompare ens. ;A F ;

T =P >!4"

V S S V

"n ;G is one form of maxwell=s relations.

;0. (ccording to enthalpy @d8 & TdS E *dP999999999999999999999999999999999999999;HIf P is constant then dP & ' , en ;H ecomes

H =T >!/"

PIf S is constant then dS & ' , en ;H ecomes

H =V >!0"

S1iff. en ;J w.r.t P at constant S

%HSP

T P S

>!&"

1iff. en ; w.r.t S at constant P

%HSP

V S P

>!&&"

#ompare ens. ;/' F ;//

T =V >!&%"

P S S P

S

V

=

=

S

P

=

=

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"n ;/0 is Second form of maxwell=s relations.

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'>. (ccording to wor% function (@d( & 9SdT ? Pd*999999999999999999999999999999999999999;/>If * is constant then d* & ' , en ;/> ecomes

A =S >!&5"

VIf T is constant then dT & ' , en ;/> ecomes

A =P >!&3" T

1iff. en ;/A w.r.t * at constant T

%AT V

S V T

>!&4"

1iff. en ;/ w.r.t T at constant *

%AV T

P T V

>!&"

#ompare ens. ;/G F ;/H

S =P >!&/"

V T T V

LLLLLL

"n ;/J is Third form of maxwell=s relations.

'A. (ccording to 3is free energy ;3@d3 & 9SdT E *dP99999999999999999999999999999999999999999;/If P is constant then dP & ' , en ;/ ecomes

G =S >!%"

PIf T is constant then dT & ' , en ;/ ecomes

G =V >!%&"

T1iff. en ;0' w.r.t P at constant T

%GT P

S P T

>!%%"

1iff. en ;0/ w.r.t T at constant P

%G

PTV T P

>!%'"

#ompare ens. ;00 F ;0>

S =V >!%5"

P T T P

LLLLLL

"n ;0A is 7ourth form of maxwell=s relations.

The four types of 2axwell relations are as follows@

T P

T

V

=

=

P

T

=

=

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T =

V S =

P S V = = V S S V P S S P V T T V P T T P

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*;. +er'8e 8$(>t o,, 'soterm.

It gives the uantitative relationship etween the free energy change and euilirium constant.

#onsider the following reaction.

aA+bBcC +dD !&"

+e %now that 3 & 8 ? TS @ 8 & " E P*.

3 & " E P* ? TS 99999999999999999999999C ;0d3 & d" E Pd*E*dP9TdS9SdT99999999C ;>

ut according to I and II law@

d" & TdS9 Pd* 9999999999999999999999999999999;Asus en ;A in en ;>

d3 & TdS9 Pd* E Pd*E*dP9TdS9SdT

d3 & *dP9SdT999999999999999999999999999999999;

at constant Temperature ,dT&'@

(dG ) (Vd6

free energy change for /mole d3 & *dP

dG =RT.dP

!4"P

$n integrating the en ;G@

dPdG =RT P

3 & 3'

ERT lnP 999999999999999;H

+here 3'

& integration constant.

7ree energies li%e (,B,#,1

Pressures P(,PB,P#,P17ree energies 3(,3B,3#,31

3 & 3Products? 3 Reactants

-G( (GC1G9 ))(GA1G8))))))))))))!/"

-G( (G1cR*l#6 1G

1dR*l#6 ))(G

1aR*l#6 1G

1:R*l#6 )C C 9 9 A A 8 8

-G( (G

1G

))(G

1G

)1R* (cl#61dl#6

))(al#61:l#6

))))!0"C 9 A 8

6c.6

d

C 9 A 8

-G(-G 1R*l# C 9 ))))))))!&"6

a .6:A 8

+hen euilirium 3 &', en ;/' ecomes

=G +RT l#K

G =RT l#K

eq

!&&"

Sus en ;// into en;/'c d c d

-G( RT l#Keq

1R*l#6C.6

9

6a .6:)-G(RT l#K )R*l# 6

C.6

9 9999999;/0

A 8 eq 6a.6

:

The aove euation is %nown as van=t hoff isotherm.

A 8

*

eq

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1*. +er'8e te 8$(>t o,, 'socore o, 8$(>t o,, e

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&

p pR

% & * *

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-H & & = R *&

*

%

=-H *

% *

&

R *&*%

l#K%

l#K&

=-H *

% *

&

R *&*%

lo$K

% = -H*

%*

& 999999999999;J

K&

%.''R *&*%

The aove euation is %nown as van=t hoff euation.

11. Te e & GH>