"# ! * " '
$% " & ( ) " ' '
"$'&
Chemistry 114 General College Chemistry II
! " !
Instructor: Dr. Gregory Jursich
Email: [e-mail]
BioE Office: 233 SEO Office: Phone: [phone] Office: 3235 SEL Office Phone: [phone] Lab: 1215 SEL Lab Phone: [phone] Office Hours: MWF 12:00 12:45 pm and 2:15-2:45 pm or by appointment
+ '
need to define system: +q
,
For Quantitative Study of Energy in Chemistry
-q
+w (PV) "system" contracts
-w (PV) "system" expands
-
'
$'
'
For Quantitative Study of Energy in Chemistry +q qp +w (PV) "system" contracts -w (PV) "system" expands -q
qp -> effective heat gain/loss at constant pressure
-
'
$'
'
Heat Capacity: Cp = q/T Note: if q > 0 obviously T > 0 so Cp must always be > 0 cs = CP/m
cP = CP/n
'
'
No heat flow between "system" & "surroundings" but internal parts absorb or release a little heat, q. q = Ccalorimeter T
Sum of all q `s = 0 mix hot + cold water in calorimeter qhot + qcold + qcal = 0
'
' .
/ 0
Sum of all q `s = 0
&
mix hot + cold water in calorimeter qhot + qcold + qcal = 0 qcold + qcal = -qhot (mcsT)cold + (CT)calorimeter = -(mcsT)hot
$
" 1 & $' ' 2$ %& ' ) !23 ) ' ( 4 ' " $' '
#$ '+' " + '+' 5 #$ (
+ ' +' ' + " $ 6
$
#$ ( H
Enthalpy is a "state" property independent of path
heat, q, depends on path just like distance
State properties of "system"
3' ' . $ ' ' 7 $ $
Independent of how it gets there. Change in prop. depends only on initial & final states
State properties of "system" &) *
#$ ( H
+ )
)
change of energy under constant pressure conditions (ie., PV work is built into it)
" 8
Reactions:
$
Hr = Hproducts Hreactants
Phase Changes: solid liquid Hmelting = Hliq - Hsolid liquid gas Hvaporization = Hgas - Hliq
Changes in Enthalpy: Reactions
at constant pressure...
Reactions:
Hr = Hproducts Rxn: Hreactants
Exothermic heat is released from "chemical system" (qP <0) H < 0 Hproducts < Hreactants
Changes in Enthalpy: Reactions
at constant pressure...
Reactions:
Hr = Hproducts Hreactants
Endothermic Rxn: heat is absorbed into "chemical system" (qP>0) H > 0 Hproducts > Hreactants
Changes in Enthalpy: Reactions
at constant pressure...
Reactions: , , ./ , 01 , 34 4 5 ) Hr = Hproducts Hreactants
.
/
/& H > or < 0 ?? 4 4 - & ) 4 4
23
*
1
$
Changes in Enthalpy: Reactions
at constant pressure...
Reactions: , , ./ & , . 01 , / ) Hr = Hproducts Hreactants /& - 3 )
moles of products double? H of reaction doubles?
6 ! &
*
&
&
CO(g) + O2(g) 2 CO(g) + O2(g)
CO2(g) Hr = -283 kJ/mol 2 CO2(g) Hr = -566.0 kJ/mol
Changes in Enthalpy: Reactions
at constant pressure...
Reactions: 6 ! & & * Hr = Hproducts Hreactants &
CO2(g) Hr = -283 kJ/mol 2 CO2(g) Hr = -566.0 kJ/mol
CO(g) + O2(g) 2 CO(g) + O2(g)
7
8
4
Hr (forward) = - Hr (reverse)
Changes in Enthalpy: Phase Change
at constant pressure...
Melting: (requires heat; qP >0) "Molar Enthalpy of Fusion" Hfus = Hliquid Hsolid Vaporizing: (requires heat; qP >0)
"Molar Enthalpy of Vaporization" Hvap=Hvap-Hliq
Changes in Enthalpy: Phase Change
at constant pressure...
Intermolecular Forces vs H
Temperature Changes from Heating a Substance at Constant Pressure
Solid -> Liquid -> Gas (A-B) (D-F) (H-J)
TBP Hvap
TMP Hfus
9 3'& :*
6 &
- ) ) * *
"
8 0*
;
) )
* * & & ( 9 :, 3 ( 0 ><, 3 ( 3; " , 9: = ) # ( 3? " , : =
8* 9 :, ( ; 3 " 3 <9 = 0 ><, ( 9<" 3 3 =
) # 0* ) ) 0? 3:,3 ; @ & * * ; 3:,3 >; && & # 4 #$ 0? 3:, 01 9 : / 8 * / #$ 9 :, 01 ; 3:, ; 3 , 3 >; 9 :, 0 0? 3:, / 3 ; / 8* , ; 3:,0 9 :, >; 3
>< 3:
* )
(39.70 g)(2.280 J/g-C)(121.5 C) + (39.70g)(357.6 J/g) + (39.70g)(1.650J/gC)(23.3 C)
26.73 kJ