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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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$.%b Balances on issolutionand 'ixing processes. -age 39
pepae inlet and outlet ent$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%.