ig996 – Homework 5 – Lyon – (53565)
1
This printout should have 27 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
This homework assignment is due Wednes
day, ±ebruary 20 at 4pm.
001
10.0 points
±or the reaction
POCl
3
(g)
⇀
↽
POCl(g) + Cl
2
(g)
K
c
= 0
.
30. An initial 0
.
33 moles oF POCl
3
are placed in a 2
.
1 L container with initial
concentrations oF POCl and Cl
2
equal to zero.
What is the fnal concentration oF POCl
3
?
(
Note:
You must solve a quadratic equation.)
1.
fnal concentration = 0
.
356143 M
2.
fnal concentration = 0
.
0432435 M
cor
rect
3.
fnal concentration = 0
.
114 M
4.
fnal concentration = 0
.
0864871 M
5.
fnal concentration = 0
.
199 M
Explanation:
K
c
= 0.30
V
container
= 2
.
1 L
[POCl
3
]
initial
=
0
.
33 mol
2
.
1 L
= 0
.
157143 M
POCl
3
(g)
⇀
↽
POCl(g) + Cl
2
(g)
ini, M
0
.
157143


Δ, M

x
x
x
eq, M
0
.
157143

x
x
x
K
c
=
[Cl
2
][POCl]
[POCl
3
]
=
x
2
0
.
157143

x
= 0
.
3
x
2
= 0
.
0471429

0
.
3
x
x
2
+ 0
.
3
x

0
.
0471429 = 0
x
=

0
.
3
±
r
(0
.
3)
2

4 (1) (

0
.
0471429)
2 (1)
= 0
.
113899 or

0
.
413899
Reject

0
.
413899 as
x
because it leads to
negative concentrations For POCl and Cl
2
and a concentration larger that the orig
inal concentration For POCl
3
.
ThereFore
x
= 0
.
113899 M and
[POCl
3
] = 0
.
157143 M

0
.
113899 M
= 0
.
0432435 M
002
10.0 points
What happens to the concentration oF
SO
2
(g) when the total pressure on the equi
librium reaction
2 SO
2
(g) + O
2
(g)
⇀
↽
2 SO
3
(g)
is increased (by compression)?
1.
decreases
correct
2.
remains the same
3.
Unable to determine
4.
increases
Explanation:
Increasing the total pressure on the sys
tem by decreasing its volume will shiFt the
equilibrium toward the side oF the reaction
with Fewer numbers oF moles oF gaseous com
ponents.
IF the total number oF moles oF
gas is the same on the product and reactant
sides oF the balanced chemical equation, then
changing the pressure will have little or no eF
Fect on the equilibrium distribution oF species
present.
The amount and concentration oF
SO
2
will decrease.
003
10.0 points
The reaction For the synthesis oF ammonia
N
2(g)
+ 3 H
2(g)
→
2 NH
3(g)
is exothermic.
Increasing the temperature
applied to the system
I) increases the amount oF NH
3
.
II) decreases the amount oF NH
3
.
III) changes the value oF
K
eq
.
IV) does not change the value oF
K
eq
.
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2
1.
II and IV only
2.
I and IV only
3.
II and III only
correct
4.
I and III only
Explanation:
N
2(g)
+ 3 H
2(g)
→
2 NH
3(g)
+ Heat
Heat or energy is a product of this reaction.
If temperature of the system is increased then
the reaction will proceed in the reverse di
rection until equilibrium is reestablished (de
creasing NH
3
).
K
eq
is temperature dependent
so changing the temperature will change
K
eq
.
004
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 Spring '08
 DavidVandenbout
 Equilibrium, Reaction, Kc

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