Born Haber Prob 2011
-
Upload
hema-bhaskar -
Category
Documents
-
view
225 -
download
1
Transcript of Born Haber Prob 2011
-
7/26/2019 Born Haber Prob 2011
1/2
Chem 1711 Born-Haber Cycle, Practice Problems
1. Given the following information for magnesium, oxygen, and magnesium oxide calculate the second electron gain
enthalpy for oxygen {i.e. for O(g) + e!O2(g)}.
for Mg (s), !Hsub= +148 kJ/mol bond dissociation energy for O2= +499 kJ/mol
1stionization energy for Mg = +738 kJ/mol 1stelectron gain enthalpy for O = 141 kJ/mol
2ndionization energy for Mg = +1450 kJ/mol for MgO (s), lattice energy = +3890 kJ/mol
for MgO (s), enthalpy of formation = 602 kJ/mol
2. Consider an ionic compound MX2where M is a metal that forms a cation of +2 charge, and X is a nonmetal that forms an
anion of 1 charge. A Born-Haber cycle for MX2is given below. Each step in this cycle has been assigned a number
(1 7).
M (s) + X2(g)
MX2(s)
M2+(g) + 2 X-(g)
M (g)
M+(g)
2 X (g)
1
2
3
4
5
6
7
a. Identify one step (1 - 7) that is endothermic as written. ______________
b. Which step (1 - 7) corresponds to !Hosub? _____________
c. Which step (1 - 7) corresponds to !Hof? _____________
d. Use the following energy values to calculate the lattice energy (in kJ/mol) for MX2.
!Hosub= 296 kJ/mol; !Hof= -421 kJ/mol; 1
stionization energy = 378 kJ/mol;
2ndionization energy = 555 kJ/mol; bond dissociation enthalpy = 310 kJ/mol;
electron affinity = -427 kJ/mol.
-
7/26/2019 Born Haber Prob 2011
2/2
eh#{B
C)\eM lltl
i.
( i ivcrt
tho 'oiio*' irrg rt i 'orrrrt t i icr ir
'or r lzigircsii i l i ' l ,
; ; iygcil,aii icl
cn tha lp l
lb r
oxygen
{ i . c .
fo r O
(S) . '
o -
+
O2
(S)}
Born'Haber
CYcle,
Practice
Problerns
, . - . ' , . ' . . ' . . ; " " . . ' . i . 1 , ' . ' . , l , . r r l , , l r . t l r . { , ' r r t r l r ' l l r ' l l ( t l l
u i l l l l
t l t ( l l r l L . \ r L r r r l
lbr Mg
(s),
AH., , . ,
+148
k.l/ lriol
l ' ' ionizal ion
ncrg) ' for
Mg
=
+738
k. l /mol
2'r ioniz.ation
nerg_\'
irr Mg
=
+1-l-50
. l / rnol
boncl
l issociation
nergy
'or .
=
+-199
J/rnol
l"
elcct t 'ot t
ain
cnthalpy
'or
=
-l '11
k.l/mcll
I-or
MgO
(s),
eitt icc
rerg)'
+3890
k. l / t t rol
1'orMgO
(s),
cnthalpy
f' lbnnation
602
k.l/rnol
aHl
=
a[l*t
lEk
+
2^tE
n
fa(a$uss)
r
+
\ s + 8 4
2 l A E 4 - L E
1 ( s )
+
a,l"{5u{-
NU
)
ts4
$
ru
*$o-ri
*^u0
ry'*'J)+
'/z
0e
J
)
-t
tt"+
J,r.co*airr)
o
tt)
rs\;de
o-Ls
z"[ea
or- J
N.tJ
o
s)
. 2"te=
+r"rrl,u';:iil^il
tlo=
[-uoe
3rqo-
qt
?38-'T;l':#
2 .
(lonsiclcr
n
ouic cornpotrncl
X.
anion
1' - l
chargc.
A Llorn-Hatre l
( t
- 1 ) .
= t Sttt{Kv-ol
w,hcrcM
is a
rnct l l that
l 'onns a cat icln
o1'+2
chargc,
ancl
X is
it t lort tr letal
ltat
orms
an
c1,clc
or MX.
is
given bclon,.
l lacli stcp
n
tl i is cycle
hiis bcen
assi-9ncd
rtutt tbcr
ri. Idcnti l '1'onc
tcp
l
-
7) that s
crldothcrmrc
s
wrrtten
b.
Which
step
1
-
7) corrcspouds
o
AHu.,,s'?
3, ' l
r
5,
o
NL\:
(s )
Which stcp I
-
7) corlcsl.rott t lso AH"t: , '
L . lse
he b l lo rv ing
ncrgy 'va l r rcs
o ca lc t t la tc
hc
at l ice
cncr .gr ' ( in
J /nro l )
i r r ' l \ ' lX .
AHu.ul,
296
k.l/nrol;
AI ' lu,
=
-'12
lt . l /nrol;
l ' t iott iz 'at ion
trcrg\ '-
378
k'l/rrtol;
2 ' ) ( l
o r r iza t io '
nc rgy -5-5-5
. l /n ro l ;bonc l
issoc ia t iop
ntha lp l '= .1
0
k . l /n ro l ;
clectron
afl ' inrt1'
-127
k.l lnoI.
+
ls+JE
z"dTE
+
AHa;s ,
2( r4)
-
LE
+
lsl j - t
+znA:- ,E
al- la iss
z(i l
-aHl
i \ l
(s )
- l
i
.j"*'
+
l , ( g )
. l
+
l r t :
(g)
I
r l
I
+ X l
( g )
t \
l
\
* \
z i ( s t
\
3
AHr
=
aHJ"ub
AHj'^b
: $ -q , ,+ -18+sss+10+ Gqa-r )
kL tL ' t
tV*o l
L-
b
lsfhce
vJJ
=.
+
llot
K{n^ut
-=#=-==-