f ^ r ^
-
T ) e ^ - a . ' - c t
feed
2.9
IV
A
^
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CHEMISTRY 102B/C
Hour Exam III
J3_
Fall 2014
Page 1
1. Consider the following reaction:
4N02(g)
+ 02(g)
y
2N205(g)
K = 6.2xl0-' -
h.c-Hy^^^CZ.c-^
I f 4.0 moles of NO2 and 4.0 mol of O2 are placed in a 2.0 L container, what is the
^
equilibrium concentration of N2O5?
4, 2 y (t>"'° ^
^ ^^
— X
1.4x1^2^
d) 7 . 0 x 1 0 ^ 3 ^
b) 4.0 X 10-2 M
c) 8.0 X 10-2 M
, Vr""^^
e) 2.5 X 10-3 M
Consider the following data for the next two questions:
3
Specific heat capacity of ice = 2.03 J/°C • g
'3
pSpecific heat capacity of water = 4.18 J/°C • g c? = L^o^ \^ - 6 . ^ 2 .
Specificheatcapacityofsteam = 2.02 J / ° C . g
^
AHfUsion = 6.02kJ/mol
^ 3 = H j ^ x / ^ . e ' 2 c j y /^t;.<3t-/^^32-Tfr<5^
AHvaporization = 40.7 kJ/mol
2.
3-5
Consider a 1.00 mole sample of ice at -30.0°C, which is heated to steam at 140.0°C.
Calculate q for the entire process.
% " Ze2.
x (^•^^^^'^(D.O^C ~i '^^^
a) 123 kJ
3
{5—3.
^
'3
b) 1070 kJ
c) 6.75 kJ
d) 234 kJ
( ^ ^ 5 6 . 8 kJ
^ 3 3 ^ /tJ
3^
^ ^ ^
A 500.0 g sample of an element at 195^C is dropped mto an ice-watermixture. 109.5 g
of ice melts and an ice-water mjxture remaii;
element.
a) 2.67 Jf°C . g
(J
(^_g)0.J75 J/°C . g
cj 0.789 J/°C . g
d) 1.62 J/°C. g
ieb-of the following mathematical relationships is falsej
-Tb)
At constant pressure^q-AE + P A V / i r f = A E
AHsystem
AHuniverse
T
AHsurroundings"^"""-^
d) At constant volume, A E - q .
-fe)
tAt^rft.''- W ' ^ j ^ " ' * , ' ! ' ^ ' ' '
1^^ ^.,4^.^
V, <o = ^ ;
Foracyclicprocess,w = -q. C o ' C ^ c l t c ^ f c ^ J ^
- <;-*'<^,A£-?^0,Af
i5=?^'<'/s<"<^
•
CHEMISTRY 102B/C
Hour Exam III
1
^^3.
Fall 2014
Page 2
Consider the following reaction:
22N02(g)
N02(g) = ^ 2
2N
NO(g)
0 ( g ) + O2
02(g)
K = ?'
^-^
4.0 moles of NO2 are placed in a 1.0 L container and are allowed to react to reach
equilibrium. At equilibrium the concentration of NO(g) is .1.0 M. Calculate the value of
the,equilibrium constant, K, for this reaction.
^ — tnXf^ » 1/ - (JLx )^CK)
/5)0.056
hl^
6.
rTTT
b) 0.11
c) 0.17
d) 25
e) 590 V^'®"^"^-^
The Ksp valueWBaF2 is 5.0 < 10"^ When 10.0 mL of 0.010 M NaF is mixedvTith 10.0
mL of 0.010 M B a ( N 0 3 ) 2 , will a precipitate form? tO^v-^w eqoa\ c^r^ c^8^^^
a) No, because Q = 1.0 x 10~^ and since it is greater than Ksp, no precipitate will mrm.
b) Yes, because Q = 1.0 x 10"^ and since it is greater than Ksp, a precipitate will form.
( T w N o , because Q = 1.3 x 10"^ and since it is less than Ksp, no precipitate will form.
d) Yes, because Q = 1.3 x 10"^ and since it is less than Ksp, a precipitate will form.
\.
J
The reaction for the formation of the complex ion Cu(NH3)4
r
is:
Cu2^(aq) + 4NH3(aq) ->Cu(NH3)4'"(aq)
/ I
"g^^y
"
^c^^t^^^/fJj]^
Which of the following is the correct expression for the equilibrium constant, K , for this
reaction?
1
[Cu^nCNH,]
K = —^
[Cu'^]msT
O
8.
U Ji3
' '
[Cu^^][NH3r
[Cu^^][NH3]
f 7 \ tCu(NH3),"]
"
[Cu^n[NH3r ,
The heat capacity of a bomb calorimeter was determinea by combusting 6.79 g of CH4
(energy of combustion of C H 4 == - 802 kJ/mol C H 4 ) ; the temperature of the bomb
calorimeter increased by 10.8°C. In a second experiment with the same bomb
calorimeter, combustion of a 12.6 g sample of ethyne, C2H2, produced a temperature
increase of 16.9°C. Calculate the energy of combustion of C2H2 in kJ/mol.
a) - 3 1 A kJ/mol
d) -532 kJ/mol
fbT)-l .10x10^ kJ/mol
e) 340. kJ/mol
c) 1.47 x 10^ kJ/mol
^ ^
.
ap
4
CHEMISTRY 102B/C
Hour Exam III
9.
Fall 2014
Page 3
Consider the following reaction which has an enthalpy change of A H T :
A -> X
A H = AHT
This reaction can be broken down into a series of steps as shown in the following
diagram:
B
^
AH,/
Which of the following relationships must be true for this reaction?
A H T - AHi - AH2 - AH3 = 0
b) AH2 - (AH3 + AHI))^AHT
c) AHT + AH, + AH2 + A H ^ y f | : i 4 f i r d ) A H T +
AH2)4 AHi + AH3
e) AH3 - (AHi+AH2))(t)
10/-9
^ I
10.
. 2,
Consider the following reaction at some temperature:
If initially 3.00 atm of F2 and 3.00 atm of CI2 are reacted in a rigid container, calculate
the equilibrium partial pressure of CbCg). r i jn
A
I,
^ ^
K J_ 11.
1^
|<f
a) 0.25 atm
b) 0.50 atm
d) 1.5 atm
e) 2.0 atm
^c)7l.0atm
^
-
^;—:=:^ \ ^
_//
%
— A 50.0 mL sample o f 0.200 MCa(N03)2 is mixed with 50.00 mL of 0.200 MNaF. When
the system has come to equilibrium, what are the equilibrium concentrations of Ca^* and
[Ca^1e
a)
5.0
X
10-2 M
b)
1.0
X
10"' M
c)
2.2
X
10"^ M
d)
1.0
X
10"' M
5.0
X
10-2 A/
_3
7
l.OxlO-^M
M^-^^ ^'^^"^
2.0X10-5M
^
J
^ ' ' ^
' / ^
f^-^^U.
CHEMISTRY 102B/C
Fall 2014
Page 4
Silver acetate (AgCiH^O^)
gC2H302) is
is^aa sparingly
sparmgly'soldble'salt
soluble salt wit
with Ksp= 1.9 x 10"^. Compare the
effects on the solubility of silver acetate by addition of HNO3 or by addition of NH3.
^
a) Addition of either HNO3 or NH3 would decrease the solubility of AgC2H302.
b) Addition of NH3 would increase the solubility of AgC2H302, but addition of HNO3
would decrease it.
c) Addition of NH3 would increase the solubility of AgC2H302, but addition of HNO3
would have virtually no effect.
Addition of either HNO3 or NH3 would increase the solubility of AgC2H302.
e) Addition of NH3 would decrease the solubility of AgC2H302, but addition of
-Would mcrease it.
13.
[3
Using the Dona energies below, estimate the enthalpy change in kJ for the reaction:
15
H
H
o
H-^0-
I
I
-c-
-C
T
H
Bond Energy (kJ/moD
C-0
c=o
0-H
C-C
H-H
If
J314,
^
e^h^'^^^
H
r
c\r . U
358
745
467
347
432
a) AH = -2654kJ
/ ^ A H
/V
H + H2O
b) AH = -567kJ
= OkJ
c) AH = 567
e) AH = 1258 kJ
An equilibrium mixture for the reaction:
IT
2NH3(g) ^
N2(g) + 3H2(g)
contains 9.0 mol N2,6.0 mol H2, and 6.0 mol NH3, all in a 3.0 L container at a certain
temperature. Calculate the value of K for this reaction at this temperature.
a) 2.0
b) 4.0
d) 9.0
e) 12
c) ;6.o
3^0(2^)
-^3
Aj> CHEMISTRY 102B/C
Hour Exam III
^
5
^
Fall 2014
Page 5
Aluminum fluoride has a solubility of 6.66 x 10"^ mol/L. Calculate the K..
AlF3(s).
1^^^ ^ S ( 3 s 3 ' ^ ^ ^ ^ pr^Uem^
1
J3
-i^^
^
_
a) 4.44 xlO"^
b) 1.97x10"^
5.31 x 10-^
e) 5.90 X 10"^
c) 5.90 x i O ' ^
_
Calculate the molar solubility of Ag2C03(s) in an aqueous solution that is 0.50 M i n
K2CO3. Ksp for Ag2C03 = 8.2 x IQ-'^
^ rt^^:.^Cg'/A^ ; l AJ"
) 2.0 X 10"Vol/L
d)
a; 2.8
z.o X
^ IQ-^
l u mol/L
moi/j-.
[Jif
17.
b) 2.6 X 10^mol/L
^S I-^M
i Lx^ lu
0
J.H
a) 248 kJ
*\
/iy)A2ia
c) 864kJ
f/C
d) 92kJ
/^TZZT^i
e)_184kj_
'
I . 15 J 01work is done on the system, while 30 J of heat
--^ IS- absorbed by it; then:
II. 20 J of heat is given off by the system, while^^25^^^work is done by the system.
19.
b) -30 J
c) 40 J
d) 45 J
Consider the reaction:
NH4N03(s) ^
/eV)0
^
N20(g) + 2H20(g)
K = 4.85
,
r
f
/
200. g of NH4N03(s; are placed in a reaction vessel containing H20(g) at a concentration
of 2.0 Mand N20(g) at a concentration of 2.0 M. After equilibriiun is reached, will the
mass of NH4N03(s) increase, decrease or remain unchanged?
a) The mass of NH4N03(s) will decrease (< 200. g).
The mass of NH4N03(s) will increase (> 200. g).
c) The mass of NH4N03(s) will remain unchanged (= 200. g).
\
A(4-^<^3^A)
J
^ ^3 < ^ ' ^ ' ^ ^ ^
"
/z-''^ ^
Determme AE fof a systeni which undergoes both of the following two processes:
a) 30 J
|T_2-
_ \
/:
AH° = - m
AH°= 432 kJ
AH°= 240 kJ
calculate the bond energy of the H - C l bond.
2^
mol/L
moi/JL ^
.
Given the following set ot gas phase reactions:
H2 + C l 2 ^ 2 H C l
H2^2H
Cl2^2a
T 18.
c) 1.3 x 10"* mol/L
/
_ .
(L
C H E M I S W 102B/C
Fall 2014
Page 6
^-^t^"^'
17- 20y/^ Consider the following endothermic reaction at equilibrium:
Which of the fol^wmg would cause t l ^ reaclio^to^s^ift toward reactants (shift left) to
reestablish equilibrium?
.
Adding H20(g). -^S^ ^cLsect^
re^UJ/sf^^^^^^takA.
Increasing the temperature. ^ACdL<::4(^.^^^, re<yL<L4->«^ ^ k.*^^5
< ^ rix>es^^^
Adding Ar(g) (assume a constant volumexontainer)
e^f^ist^c<
^^^^^J^^^^^
Increasing the volume ofthe reaction contamefr^
^f^^^'^^
^
j : , ^ ) AddingSiH(0H)3(s).
a ^ ^ J J : ^ ^ ! ^ , ^
^ees
^Oa)
c^b)
^^^)
v^<5d)
J- \^ 21.
How many of the following five quantities is/are state functions?
work
|1. enthalpy^
III, highway distance from Peoria to Champaign
fTV. p r e s s u r e ^ (^"teS^^rature-^
4 ' ^ ^ ' ^ ' ^ ^ AUe-fe<r>-^f-.4^fiK5
a) none
b) 1
c) 2
C^l__j) e) 5 (All are state functions.]
aoV
<->rtc
ci§4?fi?e^ti4^ii:iif::^^
,
CasPzCs) + 6 H20(l) -> 3 Ca(0H)2(s) + 2 PHsCg)
AH = -721.70 kJ
I f this reaction were carriea out at 298 K in a beaker open to a constant-pressure
atmosphere, which of the following would be false?
T ^ ) w = -4.96kJ
d) The reaction is exothermic.
7-c)
3
qp = -721.70 kJ
^^i^cf^^
e) Heat is released.
The following reaction was studied in a coffee cup calorimeter:
2 HCl(aq) + Ba(0H)2(aq) ^ BaC^Caq) + 2 HaOO)
AH = -118 kJ
In the coffee cup calorimeter, 100.00 mL of 0.500 M H C l was mixed with 300.0 mL of
0.500 MBa(0H)2. Assuming a solution density of 1.00 g/mL, a solution heat capacity of
4.18 J/°C. g, an mitial solution temperature of 25.00°C, and no heat loss to the coffee
cups, calculate the final temperature pf the reaction mixture.
i / i
1
I
a) 23.24°C
b) 25.92°C
Kecci- relecLS^cd-^^'^^rc^hc^
^ci"^
fc^C«,t©Ar^*4^r
c) 2.89°C
d) 27.89°C
^ ^ , ^^^^"^""^C-J^^^
= Aecyl- loss: -f/e^
re^i^o'^
(^^6J6°C
'^^'^
'
^
'^"^^
- P-^SO J
J)
C
CHEMISTRY 102B/C
Hour Exam III
1.
24.
/I
Fall 2014
When ethene gas, C2H4, is combusted at 298 K, C02(g) and H20(l) are produced. The' ^
enthalpy of combustion of ethene at 298 K is -1411.1 kJ/mol ethene. Given the
following standard enthalpies of formation, calculate the standard enthalpy of formation
for ethene.
^
AHf°
C02(g)
-393.5 kJ/mol
-285.9 kJ/mol
H20(l)
^ ^ 2 . 3 kJ/mol
d) -126.2 kJ/mol
•25.
^0
e) -296.0 kJ/mol
Ksp value for La(I03)3.
1.0x10
d) 2.7 X 10,-27
26.
5 l 3
c) -2769.9 kJ/mol
The solubility of La(I03)3 in a 0.10 M K I O 3 solution is 1.0 x 10 ' mol/L. Calculate the
a)
Z^jJL
b) 731.7 kJ/mol
LaSK^^)^'^ ^
^
b) 2.7 X 10-9
1.0x10-'°
e) 6.2 X 10
Consider the following five reactions: ^
L
La^^ + 3 X C ^ '
^
^
n.^^
^
^
P4(s) + 6Cl2(g) ->4PCl3(g)
IL P4(s) + 5 02(g) ->P40io(g)
m. PCl3(g) + '/2 02(g)-» Cl3P0(I)
(^v.
pci3(g)+ci2(g) -> v c g ^
V. P40io(s) + 6 PClsCg) ^ 10 Cl3P0(l)
C€>a
^
SoUc^^
/i^^u((^\
For which reaction should bond energies give the best estimation for AHreaction?
a) I
27.
b) II
V.
f ^ I V _ ee)) V
c) III
T T T r f r
c-
f(
foUov^ng compounds
Which of the following
compound; h ^ t h e smallest molar solubility (mol/L) in water?
_32 ^ j f s V ^ s - j ^ ^ ; M ^ l L , J Z k
a) A1(0H)3
Ksp = 2 X 10"-
bycds
Ksp = 1 X lO"'
c) PbS04
Ksp —1 X 10"'
d) Sn(0H)2
Ksp = 3 X 10"-
e) MgC204
Ksp = 9 x 10"
.-5
102B/C ^ - ^ ^ / c C / / ^
Hour Exam III
C ft
+ r
^fl*^<^r'
'^"'(•f
CHEMISTRY
J2SA^
yh
Fall 2014
Page 8 .
Consider two salts, PbXi and PbY2, both of which have very similar Ksp values.
Assuming H X is a strong acid and H Y is a weak acid, which salt is more soluble in acidic
solution? 5 , ^ , ^ ^
Is
OL^><s^
OL S 4 r < S ^ cS.C,^c£|,
28.
O c v d J t o ^of<^^^*^5 C>c;''t<.^>n n £ f r < ; < ^ c ^ ^ ' A | ^
rb5)PbY2
c) They should be equally soluble in acidic solution.
0^i2^
a
29.
-
f~
The standard enthalpy of formation for liquid water is -286 kJ/mol. For which of the
following reactions does AHreaction = -286 kJ?
^^,^M^^
a) H 2 0 ( l ) ^ 2 H ( g ) . 0 ( g )
b) 2H(g) + 0(g)
H20(l)
( ^ H 2 ( g ) + '/a 02(g) ^ H20(l)
d) H20(l)^H2(g) + '/202(g)
e) H20(g)-> H20(l)
^\Jis>^
2,0 2,0
.j
30.
^ CubsU^^^
^
^
t^^OC^^
e t ^ ^ ^ ^ S ^ R . ^ * ^ ^
ai[
>K ^ e ? r
^GosiX^^'^
C
-VC^ ^ e ^
c^/i ^ ^ C y 6 s W <
s4tiKi2oL/-^54<t+e5f4c5)^^2ppJ
CO'^rccJ-.
?5
F^€)f-^eou^^^
Consider when 1.0 mole of A(g) and 1.0 mole of B(g) are added to a 2.0 L container and
the following balanced reaction occurs:
«
A(g) + 2 B ( g ) - ^ 2C(g) + 3D(g)
^
^
e^cirV^(^^^^/^^'"
Which of the following statements must be true regaraing this reaction once equilibrium ^^-^^
has been reached?
^^
^t?
I^T a) The value'of t h f e q i n l i b r i ^ constant for this reaction must be greater than 1 (K > 1). p"^^^^^^
|P---b) The
rr
ofllSe^equi^briun/Constant for this reaction must be greater than 1 (K < 1).
c) At equilibrium, the^rate of the reverse reaction must be greater than the rate of the
forward reaction, ftf^f &^U((iDr^i^^/ rorfe / a r w a n ^ ^ ro^+e re^K^^t-S^-r
\ d) At equilibrium, the concentration of B(g) must be equal to the concentration of C(g)
([B],=[c].).
(Q)JAt
m^=&s^-^^r
^J-^^'^K^o,
equilibrium, the concentration of B(g) must be smaller than the concentration of
A(g)([B]e<[A]e).
31.
ic-ie-^'';
OJe-"^'-^^-^^
^^'^^
r ^ ^ e ^ ^ ' ^ ^ ^ ^ '
M y chemistry 102 exam should be graded witn the answer sheet associated with:
a) Form A
b) FormB
c) FormC
d) FormD
e) FormE
6^-
Yj-