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Thermo chemistryThermo chemistry
The study of changes in heatThe study of changes in heat
energy during chemicalenergy during chemical
reactionreaction
ExothermiExothermi
ccReactionReaction
EndothermiEndothermi
ccReactionReaction
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A chemical reaction that givesout or release of
heatenergy to the surroundings
Exothermic ReactionExothermic Reaction
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Physical Processes
MeltingBoiling
CondensationSublimation
Exothermic Endothermic
Dissolving an alkali or
concentrated acid in water
Dissolving ammonium salts,potassium salts or
thiosulphate salts in water
Dissolving anhydrous saltssuch as anhydrous copper(II)
sulphate in waterHeating of hydrated salt
Freezing
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Exothermic Endothermic
1. Comustion of fuel!. "urning of metal#. $eutralisation%. &espiration
'. &usting of iron. &eaction of reactive metal
with acid. &eaction of caronate with
acid*. &eaction of alkaline metal
with water+. Haer process
1. hermal decomposition of
nitrate salts!. hermal decomposition ofcaronate salts
#. &eaction of acid withhydrogen caronates
%. -hotosynthesis
Chemical Reactions
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Energy Change DuringEnergy Change During
Formation And Breaking OfFormation And Breaking Of
BondsBondsChemical Reaction
bond breaking and bond
formation!absorb energy" !release
energy"
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If heat absorb to break the bondshigherthan heat releasedduring
formation of bonds - endothermicendothermic
If heat absorb to break the bonds is
lo#erthan heat releasedduringformation of bonds - exothermicexothermic
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E$ER%& 'E(E' D)A%RA*E$ER%& 'E(E' D)A%RA*
Every chemical substances
have certain amount of chemicalenergyanddi+erentfor dierent
substances.
Symbol is,,The amount of heat energy released orabsorbed during chemical reaction heat of
reaction.
Symbol is --,,, unit./ mol./ mol0101
! " Total Energy Content 2roduct # Total EnergyContent Reactant
" ,3roducts
- ,reactants
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The Energy $evel %iagram &or
Exothermic Reaction EndothermicReaction
Reactants
Energy
2roducts
H = - xKJmol-
Reactants
Energy 2roduct
s
H = !"KJmol-
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A22')CAT)O$A22')CAT)O$
A 'lastic bag containing se'aratecom'artment (thin )lm* of +ater solidammonium nitrate 'laced in a 'lastic bag
Sueeed it, the com'artment broken andsolid ammonium nitrate dissolved in +ater
Endothermic4 'rovide instant coldness
COLD PACK
Other substance :Ammonium chloridePotassium nitrateSodium thiosulphate
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A 'lastic bag containing se'arate
com'artment (thin )lm* of +ater anhydrous calcium chloride 'laced in a'lastic bag
Sueeed it, the com'artment broken andanhydrous calcium chloride dissolved in +ater
Exothermic, release heat
HOT PACK
Other substance :Anhydrous magnesium sulphateAnhydrous copper(! sulphateCalcium o"ide
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5 ty3e of heat of5 ty3e of heat ofreactions reactions ,eat of 2reci3itation
,eat of$eutrali6ation
,eat of Dis3lacement,eat of Combustion
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H#AT O$ P%#CPTATO&H#AT O$ P%#CPTATO&
m
m#
D#$&ATO& :,eat of 3reci3itation is the energy change
'hen mole o) precipitate is )ormed'hen mole o) precipitate is )ormedfrom itsions7To calculate Heat of Precipitation
Ste$ find energy change , /
/ 0 mc
m = m1 + m2c = 4.2
= temp change
Ste$ # find mol, n oth solution n 0 231444
Ste$ % find H
H 0 /3 n 56 mol71
7- - -- - - -7- - -
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H#AT O$ DSPLAC#*#&TH#AT O$ DSPLAC#*#&T
D#$&ATO& :
!eat of dis'lacement is the energy change mole ofmole of
metal is displaced from its salt solutionmetal is displaced from its salt solutionb" moreb" moreelectro$ositi&e metalelectro$ositi&e metal
m
89cess metalTo calculate Heat of Displacement
Ste$ 'find energy change , /
/ 0 mc
m 0 m
c 0 %.!
0 temp change
Ste$ # 'find mol, n solution n 0 231444
Ste$ % 'find H
H 0 /3 n 56 mol71
7- - -
- - - -7- - -
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H#AT O$ +T%ALSATO&H#AT O$ +T%ALSATO&D#$&ATO& :
!eat of neutraliation is the energy change +hen
mole o) 'atermole o) 'ateris formed from the neutrali,ationbet+een mole o) H- ion )rom an acid and mole o) H- ion )rom an acid and
mole o) OH. ion )rom an al/alimole o) OH. ion )rom an al/ali
acid
m
(l)ali
m#
To calculate Heat of Neutralization
8te3 1 8te3 1 )nd energy change , / / " mc m " m0 m1
c " 2.1 " tem' change
8te3 9 8te3 9 )nd mol, n both solution n " mv30444
8te3 : 8te3 : )nd !
! " /3 n 56 mol-0
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H#AT O$ CO*0+STO&H#AT O$ CO*0+STO&D#$&ATO& :
!eat of combustion is the heat given o +hen
mole o) alcohol is burnt completelymole o) alcohol is burnt completelyin an e7cessof 81gas.
To calculate Heat of Combustion
8te3 1 )nd energy change , / / " mc
m " 1OL+*# O$ 2AT#%USED
c " 2.1 " tem' change
8te3 9 )nd mol, n(FOR F;E'< A'CO,O'*
n " 9ass 8f Alcohol
:sed9olar mass of