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Chemistry- 431f
September27,2006
Exam#1
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(20)1. Matching(usea letteronlyonce)
Accordingto the first law of themodynamics
AU equals C-
a. dFI/dT
b. third
The relationshipbetween internalenergyand
enthalpyis
O
c.q+w
d. aHt.unr/T
The entropychangefor heatinga solid
f
at constantpressureis
e. nRIn(TzlTr)
f.H-TS
The heatcapacityat constantpressure,Co,
equals A,
g. - Pr^AV
h.U=H+PV
The expressionfor pressure-volume
work is
n
-v-
i. zeroth
j. du/dT
F(s) is the distributionof speedsand
the averagevaluefor s , <s>, is
given by n
k. dqr.u/T
l.q-w
fD.
The entropychangefor a phasetransition
at constantpressureis given by
d
-Qirevv *
Qrev
n. JsF(s)
ds
o.H=U+PV
A smallchangein entropy,dS, is defined
ur ln.
."
P' AG,r"nr/T
q. Jr'(s)as
"The
entropiesof all perfectlycrystalline
substances
are the sameat T = 0K " is a
statementof the b
law of
thermodynamics.
r. Coln(T3lT1)
s. dwr"u/T
t. P"'av
The,.Gibbs
freeenergyG is definedas
+
-r.
(20) 2. The constantpressuremolar heatcapacityof prolineis 151.2J K-' mol
a. How much heatmust be addedto proline,
at constantpressure,to increaseits
'4
*o.tc
temperature
from 25'C to 50"C?
l
r a Lr,4
t\or=
lIH-_- LSL-A T
x 25K=
[,r
\'78o T/*.(
: 3.re )r.T/,-ol
b. What is the entropychangefor the aboveheating?
A S= lst z+ T . -!-^ -5
z_c{FK.
:- tT'z f
1q_,^ol
K-,*r(
(10) 3. For a certainprocessa systemabsorbs50 kJ of heatand does30 kJ of work.
What is AU for this process?
/ U - - 1U+
( ^ / - s- o - f , o :
| l _
ac,laJ
(10) 4. The enthalpyof vaporizationof methanolis 35.27kJ/mol at its normalboiling
point of 64.1"C.Calculatethe entropyof vaporizationof methanolat this temperature.
(r4 L"L t ;'?3 ?
A S = -A
li 'v
33? K
-- 35?aoT
:- Lo4. 6 :i\(- r"^oI
(15) 5. The reactionfor combustionof glycineat 25 oC is
NH2CH2COOH(s)+ 9/4 Oz(9 --- 2 COz(B)+ 512H2O(l) + l/2 N2(g)
The heatsof formation for the reactantsand productsare:
- 969 kJ mol; CO2(g), - 393.51kJ/mol;H2O(l),-285.83kJ/mol.
NH2CH2COOH(s),
a. Calculatethe enthalpychangeAH.?" for this reacrion.
C - ? c ? J=
siz x t-res sr)+ ? *(- 3?3's4
4 Hn^ = s 32.6-hT
I
b. Calculate the reaction's internal energy change AUr*n
H . = & r - P V^ \
AH:4utAOV\
4n= e'1--zt/+='/+
o^(7 (-u.{ J'- 3as'd
Att = lS"z Gt:y, -An^T ----S3z.U trf
'-
(o JaT
< ) . e s x8 . 3_-i + a z t d - x=---_-
(10) 6. Circle the following processesthat absorbheatand are endoiheilic'
t .,-. b
dr^=-S32.6-o-h
.- -s 33 .?- hT
a. protein folding from a p-sheetto an o -helix structure
@melting ice
o
c. combustionreaction with AHr*n = -L265H
d. condensationof water vapor to form liquid water
@Ctrtu-* 2CHt
(15) 7. Use the following bondenergiesto approximatethe heatof reactionfor
2 CzHot 02 ---+2 CzHsOH
AH(kJ/mol)
C-C
344
C-H
4r 5
Oz
498
c-o
350
463
o-H
O v"n"lt
[\ ru .""[.
t .,.J5
L ,rLcn'
z- (^c+
LO--
=__>__:--
L.x4t5
I:a r '-' J
o ^ J S o n^ o J
t
=
4qf
2- c-o
a o -tl
A A 3S Cr
LX 4b3
d H = A l+b"e.J.
-1"C
ti28
r
A {-J^
-lc
''- J
: LiaE
'
l
-
tGz6=-z'(f)'t