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WEEK 6• Heat of solutions and mixing• Balances on dissolution &mixing processes

• Enthalpy – concentrationcharts – single liquid phase

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8.5a Heat of solution and mixing (pg 396)

Heat of mixing (involve

mixing of two uids) heat of solution (involve

dissolution of solid o gas in a

uid)

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  Heat of solution! Hs ("!)#

When 1 mole of solute (gas orsolid) is dissolved in r moles ofa liquid solvent at a constant

temperature, T.  r = mol of solvent/mol of

solute

  W$en is ve% lage! Hs & in'nit%

  alue of Hs is availale in Table

B.11

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*efeen+e state , to %ou

+onvenient  -ue solute and pue solvent

Eg. pue Hl(g) and H/0(l) at /5o

  -ue solvent and in'nitel% dilutesolution at /5o and 1 atm

)r (HH s∆=

)(Hn)r (HnHss

  ∞∆−∆=

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Example

  al+ulate H fo a po+ess in w$i+$ /mol of potassium +%anide (K2) is

dissolved in 44 mol of wate at 18o

.  ∆H n∆Hs !"cal#

  n / mol

 

mol solventmol solute 44//44

   7Hs (ef .11)

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 "est %ouself 

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$.%b Balances on issolutionand 'ixing processes. -age 39

  pepae inlet and outlet ent$alp% tale

  :o efeen+e# +onside t$e solution as

a single sustan+e and t$e pue+omponent at /5o as efeen+e.

  al+ulate t$e spe+i'+ Hs at t$e state

tempeatue.  al+ulate t$e spe+i'+ Hs at t$e

efeen+e state

  ;dd t$e Hs

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Example 8.5<1

  *ead t$e polem

   "ansfe t$e infomation into lo+= diagam  >ael ea+$ +omponents

  ?olve t$e mass alan+e

  onvet t$e mass alan+e into molealan+e

  ?tate t$e ef state of t$e eneg% alan+e

 

 "ansfe all =nown mole! =nown H andun=nown H into a tale

  al+ulate ea+$ individual H

 

al+ulate t$e @

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Enthalpy of each stream

 

:o pue +ompound use t$e+ommon met$od i.e. pd" A

  :o solution use Hs met$od

  ould e in podu+t oea+tant steams ,

dissolution o pui'+ationpo+esses

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al+ulation of Hs

  Betemine t$e mole solventmole solute

  onstu+t a $%pot$eti+al pat$

 bas

 p p b

0

sa

H0H00

stateref s

HHH

handbook suitableanyof appendixfromCtheget...dTCH

Handbook anyorB.11Tablerefer )....1.r !C"#(HH

!a%!HCl()C"#!a%!HCl()C"#!l!&"H'C"#!g!HCl(

HHH

 ba

+=

=

==

   →     →  

−=

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$.%( Enthalpy – (oncentration (harts – single liquid phase.)age !*++#

 

 Figure 8.5.1 – Enthalpy-concentration for H2SO4-H2O

  Example 8.5-2

,diabatic mixing processAstaig$t line

+onne+ting two point will detemine t$eeCuied +ondition

  Example 8.5-3

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ommon eCuipment wo=ing undeadiaati+ +ondition

  Heate  B%e

  oole

  Humidi'e-ote w$% t$e% need adiaati+ +onditionD

 "o ma=e sue no $eat lost o ente t$e s%stem

w$i+$ +ould distu t$e oe+tive of t$epo+ess i.e +ooling$eating e+tA

 "$eefoe t$e eCuipment $ave to e insulated

a++odingl%.