Panas Reaksi 3a

7/24/2019 Panas Reaksi 3a

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Panas reaksi


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What is Energy?

A. Energyis a property of matter that allows work to be done (thecapacity to do work or to produce heat*)

B. Law of Conservation of Energy

Energy can be converted from one form to another, but cannot be

created or destroyed

Potential and Kinetic Potential energyis energy of position (interparticle forces or

intraparticle forces)

Kinetic energyis energy of motion (translational rotational!ibrational)

According to kinetic theory"

#. all matter is composed of particles

$. all particles are in motion

%. collisions are elastic


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&. 'emperatre and eat

'emperatreis the measre of KE

'hermal energy (heat content) is a measre of the KE and PE of a grop of particles.

eat is thermal energy which mo!es from one

place to another.

*. eat nits

+ole (+), the official - nit defined in terms of

force times distance (/m or kgm$0s$)

calorie (cal), originally defined as the amt. of heatneeded to raise # g of water # &1.

&alorie (&al), #222 calories # kcal sed by

ntritionists


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eat

What is heat?

t is !"# the same thing as temperature$

#emperature is a measure of how much heat can

f%ow but it is not a measure of the heat itse%f$ &eat

is a form of energy$ 's a resu%t heat is measured in(ou%es$ t is energy that f%ows due to a temperature

difference$&eat is given the symbo% 3$


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Heatis the transfer of thermal energybetween two bodies that

are at different temperatures$

Temperatureis a measure of the thermal energy$

#emperature #herma% Energy

++C++C

greater therma% energy -$.


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Energy changes in a physical change

A. As heat is added to a sbstance it ndergoes

temperatre changes (KE changes) and phase changes (PE changes).

B. 'emp changes

As we add heat to a solid li3id or gas thetemperatre sally changes. 'he amont of heatneeded depends to change the temp depends on %factors" (#) the amont of material ($) what thematerial is (%) the amont of temperatre change

needed./ 'hese factors form the basis for an e3ation"

4 5 m &p6'


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/ 4 758 + is the heat re3ired/ m 758 g is the amt of sbstance/ 6' 758 &1 is the change in temperatre/ 6' also e3al 'f , 'i where 'f and 'i represent the

final and initial temperatres

/ote"

4 will be positi!e if the temp is increasing (6' 9) and negati!e if

the temp is decreasing (6' ,).&p isthe amont of heat needed to change a nit mass ofmaterial by a nit temperatre change. t is called the specificheat capacity. :ost commonly the nits are +0g&1 or +0mole &1.'he !ale of &p changes from one phase to another and fromone sbstance to another. 'he sbscript p refers to the fact

that the is the heat capacity at constant pressre , a sitationthat is commonly encontered when processes occr that areopen to the atmosphere.


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&. Phase changes

'he abo!e e3ation can be sed for any temperatre

change where we heat a solid li3id or gas. Btwhat happens at the phase change points?

When a solid changes to a li3id or a li3id to a gas

the temp does not change ntil all the presbstance has ndergone the phase change. 'hswe add heat to a solid at the :P and the temp doesnot change. ;ikewise we add heat to a li3 at the BPand the temp does not change.


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'he e3ations that go!ern these changes are"

4 5 m f 45 m !

/ f758 +0g is the heat of fsion the amont of heat needed tochange # g of solid to li3id. 'his is a positi!e nmber. 'he!ale for the change from li3 to solid is a negati!e nmber.

/ !758 +0gis the heat of !apori


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Endothermic processes

/ Endothermic processes are those in which the

enthalpy of prodcts is greater that the enthalpy ofreactants. 6 > 2 and heat is absorbed from thesrrondings. f a chemical reaction takes place thepot feels cold. :elting is a physical change that isendothermic.

E=othermic processes

/ E=othermic processes are those in which theenthalpy of the prodcts is less that the enthalpy of

the reactants. 6 @ 2 and heat is gi!en p to thesrrondings. f a chemical reaction takes place thepot feels hot. ree


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'o calclate the amont of heat needed to go from onetemp to another yo mst"

/ dentify the phase yo are in at the beginning temp./ dentify the phase yo are in at the end temp.

/ se the appropriate steps (transitions) to get fromthe beginning to the end. Add the !arios steps

together to get the total.

/ E=ample" ow mch heat is needed to change C2.2 g

of solid ice at ,#2.21& to steam at ##2.21& ndernormal pressre conditions?

&p(solid) 5 $.2D +0g&1 f5 %%% +0g

&p(li3id) 5 .#F +0g&1 !5 $$D2 +0g

&p(gas) 5 $.2% +0g&1


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Enthalpy of a &hemical Geaction/ '%% chemica% reactions invo%ve an e0change of

heat energy, a reaction by measuring theentha%py change 1H)$"ften not possib%e todirect%y measure the heat energy change of thereactants and products 1the system)$

/ the entha%py of the reaction can be indirect%yca%cu%ated with the fo%%owing e2uation$ q HCp/m/ 3T #he term qrepresents the heatenergy that is gained or %ost$ Cpis the specificheat, mis the mass of substances , and 3Tis the

temperature change of the reaction mi0ture$ #hespecific heat and mass are used becausesubstances wi%% either gain or %ose heat energyin a reaction that occurs in a2ueous so%ution


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/ t is impossible to measre the absolte amont

of heat content () that a sbstance has. We can

only measre changes in heat content(6). Wetherefore set an arbitrary


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-ymbols

6 5 Enthalpy change for any process

615 Enthalpy change nder standard

&onditions

6f15 Enthalpy change if prodct is formed from free elements nder

standard conditions. (#he change in entha%py thataccompanies the formation of one mo%e of acompound from its e%ements with a%% e%ements intheir standard state)

'he standard states are # atm pressre and $C.221&$


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#here are 4 ways to find &

5$ 6easure it in the %ab

.$ 7se &ess8 %aw

4$ 7se entha%pies of formation


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9epresenting Entha%py Changes

Energy changes obtained from empirica%studies1ca%orimetric e0periments) can be

communicated in for ways$

/ :y inc%uding an energy va%ue as a term ina thermochemica% e2uation

/ :y writing a chemica%and stating theentha%py change in terms of ;& notation

/ :y stating the mo%ar entha%py/ :y drawing a chemica% potentia% energy

diagram


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#hermochemica% e2uations with energy terms$

Write a thermochemica% e2uationfor the burning of . mo%es of butane, C,&. k(

4$ 9eport the energy change for the reaction by writing the appropriatethermochemica% e2uation$

$&EF(g) 9 #%I$(g) F&I$(g) 9 #2$I(l) 9 CJ$ k+.


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#hermochemica% E2uations with ;& Aa%ues' second methodis to write a ba%anced chemica% e2uationfor the entha%py change andthen write the $;& va%ue beside it, making sure it has the correct sign$

E0amp%eB Write a thermochemica% e2uation for the reaction between su%fur dio0ide ando0ygen in the formation of su%fur trio0ide$ #he mo%ar entha%py is =


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What is the mo%ar entha%py of C". 1g) in the reaction forthe burning of butane be%ow?

. C&5+1%)G54 ".1g) < C".1g) G 5+ &." 1g) ;& =@45@ k(

Answer"6o%ar entha%py is the entha%py change in e2uation divided

by the ba%ance of C".1g)6o%ar entha%py, ;& substance @45@ k( H < mo% -- k(mo%$


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&ow much heat wi%% be re%eased if -@ grams of butane is burnedin a

%ighter according the e2uation in the e0amp%e above$

Answer"

5) Iiven

-@ grams of butane

;& reaction @45@ k(

.) a) 6o%es of butanemass H gram mo%ecu%ar weight 1 butane )

-@ grams H @$@ k(mo%

4) P%ug va%ues into e2uation$ J n * ;& substance

J 5$5. mo% * .-@>$@ k(mo% .>-$ k(Considering significant figures 4$+ 6(


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&ess8s %aw

/ the entha%py changes of a series of

reactions can be combined to ca%cu%ate

the entha%py change of a reaction that is

the sum of the components of the series

/ &oncept" f a reaction can be written as

the sm of $ or more reactions the

enthalpy change (6) for the o!erall

process is the sm of the 6Hs for theindi!idal reactions.


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E=ample"

$I (l) $I (g) 65 k+ $I (g) $(g) 9 #0$ I$(g) 65 $$ k+

/ What is the 6 for$I(l) $(g) 9 #0$ I$(g) ?/ Add both reactions to get

$I (l) 9 $I (g) $I (g) 9 $(g) 9 #0$ I$(g)

/ 'his gi!es the desired reaction so add the 6Hs to

get $FD k+ as the 6 for the reaction.Gemember"

(#) f a reaction mst be mltiplied by a whole nmberthe 6 for that reaction is also mltiplied.

($) f a reaction is re!ersed the sign of 6 is

re!ersed.


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Ca%cu%ate the standard entha%py of formation of C.1l)

given thatB

C1graphite)G ".1g) C".1g) &+ =44$@ k(r0n

1rhombic)G ".1g) ".1g) &+ =.-$5 k(r0n

C.1l)G 4".1g) C".1g)G .".1g) &+ =5+>. k(r0n

5$ Write the entha%py of formation reaction for C.

C1graphite)G .1rhombic) C. 1l)

.$ 'dd the given r0ns so that the resu%t is the desired r0n$

r0nC1graphite)G ".1g) C".1g) &+ =44$@ k(

.1rhombic)G .".1g) .".1g) &+ =.-$50.k(r0n

C".1g)G .".1g) C.1l)G 4".1g) &+ G5+>.k(r0nG

C1graphite)G .1rhombic) C. 1l)

&+ =44$@ G 1.0=.-$5) G 5+>.


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-ome things to remember

/ f you have to reverse a reaction to get things to

cance%, the sign of ;& must a%so be reversed$

/ f you have to mu%tip%y an agent to get it to

cance%, a%% other agents and ;& must a%so bemu%tip%ied by that number$

/ Ienera%%y ;& va%ues given in tab%es are under

5atm and .@KC 1.


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Ca%cu%ating entha%py change

5$ When a r0n is reversed, the magnitude of ;& remains

the same, but its sign changes.$ When the ba%anced e2n for a r0n is mu%tip%ied by an

integer, the va%ue of ;& must be mu%tip%ied by the same

integer

4$ #he change in entha%py for a r0n can be ca%cu%ated fromthe entha%pies of formation of the reactants and products

$ E%ements in their standard states are not inc%uded a$ For

e%ements in their standard state, ;&fK +


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Enthalpy (H)is used to 2uantify the heat f%ow into or out of a

system in a process that occurs at constant pressure$

H H1products) M H1reactants)

H heat given off or absorbed during a reaction at constant pressre

Hproducts N HreactantsHN +

Hproducts O HreactantsHO + -$4


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-$@


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Factors 'ffecting &eat or Entha%py ChangePhysical state of the reactants and the prodcts

#he ;& of a reaction depends upon the physica% states of reactants and products$ For e0amp%e, whenhydrogen and o0ygen gases combine to give %i2uid water, the heat of reaction is different than whenthey combine to form gaseous water$

4antities of reactants

#he amount of heat evo%ved or absorbed depends upon the amount of reactants$ For e0amp%e, theheat of combustion of . mo%es of carbon is doub%e than heat of combustion of 5mo%e of carbon$

Allotropic modification

#he amount of heat evo%ved or absorbed for different forms of the same substance are different$ Fore0amp%e,

'emperatre

#he heat of reaction depends upon the temperature of reactants and products$

Pressre or !olme

#he heat of reaction depends upon the conditions of constant pressure or vo%ume$ 's,

;& ;EG P ;A

;& may be e2ua%, greater than or %ess than ;E$


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/ Ca%cu%ate the standard entha%py 1heat) of

reaction for the o0idation of ammonia gasto produce nitrogen dio0ide gas and watervapour given the fo%%owing standardentha%pies 1heats) of formationB

/ !&41g) ;&fo =- k( mo%=5

/!"

.

1g) ;&fo

G4 k( mo%=5/ &."1g) ;&fo =.. k( mo%=5

/ ".1g) ;&fo + k( mo%=5 1by definition)


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5$ Write the ba%anced chemica% e2uation for the reactionB

!&41g) G >".1g) =====O !".1g) G 4.&."1g)

.$ Write the genera% e2uation for ca%cu%ating the entha%py1heat) of reactionB

;&o1reaction) &of1products) = &of1reactants)

;&o Q;&of1!".1g))G 4. 0 ;&of1&."1g))R = Q; &of1!&41g))G > 0;&of1".1g))R

4$ ubstitute the va%ues for the entha%py 1heat) of formationof each product and reactant into the e2uation$

;&o QG4 G 14. 0 =..)R = Q=- G 1> 0 +)R

$ o%ve the e2uation to find the entha%py 1heat) of

reaction$;&o QG4 G =4-4R = Q=- G +R =4. G - =.


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:enSene 1C-&-) burns in air to produce carbon dio0ide and

%i2uid water$ &ow much heat is re%eased per mo%e of

benSene combusted? #he standard entha%py of formation

of benSene is $+ k(mo%$

.C-&-1l)G 5@".1g) 5.C".1g)G -&." 1l)

&+r0n n&+1products)f m&

+1reactants)f=

&+r0n -&+1&.")f5.&

+1C".)f Q G R = .&+1C-&-)fQ R

&+r0n Q 5.0M44$@ G -0M5$- R M Q .0$+ R =@- k(

=@- k(

. mo% = .>4 k(mo% C-&-

-$@

E=ample


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E=ample

Will the reaction

PEI#2(s) 9 D $I (l) ,,> $PIE(a3)be e=othermic or endothermic?

Solution'he enthalpy of a reaction can be e!alated from thestandard enthalpies of formation of all prodcts andreactants.

Ho5Hof(all prodcts) ,Hof(all reactants)

'hs it is desirable to find the Hofof all prodcts and

reactants" PEI#2 ,%##2 k+0molM $ ,$FD k+0molM %PIE,#$FF k+0mol.

Ho5 ,N#$FF , (,%##2 ,$FDND) 5 ,%$D k+0mol.

P b t k dihit d i


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Panas pembentukan dihitung dari panaspembakaran

uatu senyawa Ca&b:rcC%dFef"g!hi, , ika ;&cada%ah

panas pembakaran suatu senyawa yang menghasi%kanproduk akhir, C".1g), &." 1%), :r 1%), C%.1g),&F1a2), 1s), !.

1g),". 1g) dan ;&fada%ah panas pembentukan B;&f =;&c=+@5,< a M 45@ b M @+5 e =>+-+ i

(ika ;&c8 ada%ah panas pembakaran terhadap suatusanyawa yang menghasi%kan produk C".1g), &." 1%), :r.1g), C%.1g),&C%1a2), 1s), &!"41a2), &."1a2) B

;&f =;&c8 =+@5,< a M 45@ b G 4->+ c M @


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Contoh B

&itung panas standard reaksi , ;&.@sbbB

CaC.1s) G . &." 1%) ==== Ca1"&).1s) G C.&.1g)

Tari tabe% 1., &ougen W$)

CaC.1s) ;&f = 5@+++ ka%

&." 1%) ;&f = -, ka%Ca1"&).1s) ;&f = .4@


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:easring heats of reaction

&eats of reaction can be measured in a device

ca%%ed a calorimeter$#his device is usua%%yinsu%ated to avoid heat %oss or gain from outside

the ca%orimeter during the reaction, which cou%d

introduce errors into the measurement$ n a coffee

cup ca%orimeter, the type used in %ab, the pressure

remains constant$ #herefore, the heat measured is

an indication of the change in entha%py of the

reaction$ n order to use this device, we must %ookat the re%ationship between the heat and the

variab%es that are measured$


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Ca%orimetry = science of measuring heat

5$ &eat capacity 1C)

ratio of heat absorbed to increase intemperature

.$ pecific &eat Capacity

Energy re2uired to raise the temp of 5 gram of asubstance by 5KC

4$ 6o%ar heat capacity Energy re2uired to raise the temp of 5 mo%e of a

substance by 5KC


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pecific &eat Capacity, c

#emperature change #

mass m

input of 2


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specific heat capacity, or specific heat

/' measure of the efficiencywith which a substance

can store this heat energy

/#he greater the materia%Us specific heat, the moreenergy must be added to change its temperature

/the 2uantity of heat re2uired to raise thetemperature of a unit of mass of a substance by aunit change in temperature$

/the specific heat of wateris given as

which means that 5$++ ca%orie of heat is necessary toraise one gram of water one degree Ce%sius, or 5+

ou%es of heat are necessary to raise one ki%ogram of

water one e%vin


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ow mch heat in Ooles is absorbed by %22 grams of water if thetemperatre change the water ndergoes is #C o& ? ('hespecific heat capacity of water is .# +0gN o&.)

#) Write down the gi!en information"

mass of water 5 %22 gramstemperatre change in water 5 #C o&

specific heat capacity 5 .# +0 g N o&

$) *etermine the information re3ired"

amont of heat in Ooles%) Analy


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&ow much heat is given off when an


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Constant Pressure Ca%orimetry 1so%utions)

5$ Ca%cu%ating &eat of 90n, ;&

;& specific heat capacity 0 mass of

so%Un 0 increase in temp

H = s x m x #

.$ &eat of r0n is an e0tensive property =

dependent on the amount of substance

;& V mo%es of reactant

Constant Pressure Ca%orimetry


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Constant=Pressure Ca%orimetry

!o heat enters or %eaves

qsys qwaterG qca%G qr0n

qsys +qr0n = 1qwaterG qca%)

qwater mst

qca% Ccalt

-$

9eaction at Constant PH qr0n


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-$

Constant Ao%ume Ca%orimetry


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Constant Ao%ume Ca%orimetry

5$ Ao%ume of bomb ca%orimeter cannot change, so no work

is done.$ #he heat capacity of the ca%orimeter must be known,

genera%%y in k(KC

Constant=Ao%ume Ca%orimetry


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Constant=Ao%ume Ca%orimetry

!o heat enters or %eaves

qsys qwaterG qbombG qr0n

qsys +qr0n = 1qwaterG qbomb)

qwater mst

qbomb Cbombt

-$

9eaction at Constant V

HX qr0n

H qr0n

C % % h f i b % i


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Ca%cu%ate heat of reaction by ca%orimetry

:ased on conservation energy %awB 4AB-IGBE*9 4GE;EA-E*5 2

f reactionsystem re%eases heat, so surroundings1so%utionwater and ca%orimeter) absorb heat$

4&A;IG:E'EG 9 4-I;'I/9 4GEA&'I/ 5 2

4GEA&'I/5 , (4&A;IG:E'EG9 4-I;'I/)

/I'EB JC'L"96E#E9 CC'L"6E#E9$ ;#

J"L7#"! m"L7#"!$c"L7#"!$ ;#

Problem -ol!ing


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Problem -ol!ing

#. Ca%cium carbide can be made by heating ca%cium o0ide

1%ime) with carbon 1charcoa%)$

Ca" 1s) G 4 C 1s) CaC.1s) G C" 1g) ;& G-$< k(

&ow many ki%oou%es of heat are absorbed in a reaction

in which >-$@ g C1s) is consumed?


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#he enthalpy of solution 1 H ) is the heat generated or


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#he enthalpy of solution1

Hsoln) is the heat generated or

absorbed when a certain amount of so%ute disso%ves in a

certain amount of so%vent$

Hso%n Hso%n = Hcomponents

-$-

Which substance1s) cou%d be

used for me%ting ice?

Which substance1s) cou%d be

used for a co%d pack?

#he o%ution Process for !aC%


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Hso%n tep 5 G tep . >


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Entha%py of vaporiSation, ;Hvap/ a%so known as the heat of !apori


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Entha%py of condensation/ 1or heat of condensation) is numerica%%y

e0act%y e2ua% to the entha%py ofvaporiSation, but has the opposite signB

entha%py changes of vaporiSation are

a%ways positive 1heat is absorbed by thesubstance), whereas entha%py changes of

condensation are a%ways negative 1heat is

re%eased by the substance)$

L t t h t


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Latent heat

/ the amount of energy re%eased or absorbed by a

chemica% substance during a change of statethat occurs without changing its temperature,

meaning a phase transition such as the me%ting

of ice or the boi%ing of water$

/ #wo of the more common forms of %atent heat

1or entha%pies or energies) encountered are

%atent heat of fusion 1me%ting) and %atent heat ofvaporiSation 1boi%ing)$


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/ #he specific latent heatis the amount of

energy re2uired to convert 5 kg 1or 5 %b) of a

substance from so%id to %i2uid 1or vice=versa)without a change in the temperature of the

surroundings == a%% absorbed energy goes into

the phase change == is known as the specific

latent heat of fsion

/ specific latent heat of !apori


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'he enthalpy of moist and hmid air consist of

sensible heat and latent heat , enthalpy is sedto calclate cooling and heating processes/ 6oist air is a mi0ture of dry air and water

vapor$ n atmospheric air, water vapor

content varies from 0to 3%by mass$ #heentha%py of moist and humid air inc%udes B

the entha%py of the dry air = the sensible

heat = and the entha%py of the evaporatedwater = the latentheat


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pecific entha%py of moist air

/ h = ha+ x hw (1)

wh!

h = spc"#"c nthalp$ o# mo"st a"! (&'g t*'lb)

ha= spc"#"c nthalp$ o# !$ a"! (&'g t*'lb)

x = h*m""t$ !at"o (g'g lb'lb)

hw= spc"#"c nthalp$ o# wat! ,apo! (&'g t*'lb)


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pecific Entha%py of Try 'ir = ensib%e &eat

ha= cpat (-)

wh!

cpa= spc"#"c hat capac"t$ o# a"! at constant

p!ss*! (&'go

C .s'g/ t*'lbo

)t = a"! tmp!at*! (oC o)

For air temperature between 100oC(120o)

and 100o

C(-1-o

)the specific heatcapacity can be set to

cpa= 1004 (&'goC) = 0-50 (t*'lbo)


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pecific Entha%py of Water Aapor = Latent &eathw= cpwt + hw (3)

wh!

cpw= spc"#"c hat capac"t$ o# wat! ,apo! at constantp!ss*! (&'goC .s'g/)

t = wat! ,apo! tmp!at*! (oC)

hw= ,apo!at"on hat o# wat! at 0oC (&'g)

For water vapor the specific heat capacity can be set to/ cpw= 165 (&'goC) = 0555 (t*'lbo)

#he evaporation heat 1water at +oC) can be set to

/ hw= -201 &'g) = 780 (t*'lb)

7sing 1.) and 14), 15) can be modified to

/ h = cpat + x 9cpwt + hw: (1b)

E % E th % i 6 i t 'i


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E0amp%e = Entha%py in 6oist 'ir#he entha%py of humid air at -2oCwith specific

moisture contentx = 00-03 g'g (sat*!at"on), canbe ca%cu%ated asB

h =(1004 &'goC) (-2oC) + (00-03 g'g)

9(165 &'goC) (-2oC) + (-201 &'g):

= (-212 &'g) + (073 &'g) + (2180 &'g)

= 886 (&'g)

//ote#he %atent heat due to evaporation of water

is the maor part of the entha%py$ #he sensib%e heatdue to heating evaporated water vapor can be

a%most neg%ected$


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