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Le Chatelier's Principle
Related Topics
Wize University Chemistry Textbook > Equilibrium
Le Chatelier's Principle
3 Activities
Given the following exothermic reaction, decide which direction the equilibrium will shift (if any) in each scenario.
CH
4
(g) + 2H
2
S(g) ⇌ CS
2
(g) + 4H
2
(g)
Part 1
Part 2
Part 3
Part 4
Part 5
The concentration of dihydrogen sulfide is decreased.
Equilibrium will shift to the left.
Equilibrium will shift to the right.
Equilibrium will not shift.
I don't know
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More Le Chatelier's Principle Questions:
Le Chatelier's Principle
In an esterification reaction, a carboxylic acid and an alcohol react to form an ester and water. This reaction establishes an equilibrium because the reverse process can also occur. If the water is allowed to boil and leave the system as water vapour, how will the equilibrium respond?
Given the following exothermic reaction, decide which direction the equilibrium will shift (if any) in each scenario.
CH
4
(g) + 2H
2
S(g) ⇌ CS
2
(g) + 4H
2
(g)
Consider the following reaction:
2 As
(s)
+ 6 NaOH
(aq)
→ 2 Na
3
AsO
3(aq)
+ 3 H
2(g)
If the pressure of the reaction is increased, how will this change the equilibrium? Why?
Consider the following reaction:
2 As
(s)
+ 6 NaOH
(aq)
→ 2 Na
3
AsO
3(aq)
+ 3 H
2(g)
If the produced H
2
gas is removed from the reaction upon being produced, which direction will this drive the equilibrium? Why?
Look at the following reaction.
BaCrO
4(s)
<----> Ba
2+
(aq)
+ CrO
4
2
-
(aq)
If PbCrO
4
is added to the solution, which direction would we expect the equilibrium to shift?
Le Chatelier's Principle
Consider the following reaction at equilibrium in a closed container:
2
H
g
O
(
s
)
⇌
2
H
g
(
l
)
+
O
2
(
g
)
Δ
H
°
=
+
181.4
k
J
2HgO(s) \rightleftharpoons 2Hg (l) + O_2 (g) \qquad \Delta H° = +181.4kJ
2
H
g
O
(
s
)
⇌
2
H
g
(
l
)
+
O
2
(
g
)
Δ
H
°
=
+
181.4
k
J
The partial pressure of O
2
may be increased by:
Le Chatelier's Principle
Consider the information provided in the table on the right for the following reaction:
H
2
(
g
)
+
C
l
2
(
g
)
⇌
2
H
C
l
(
g
)
H_2(g) +Cl_2(g)\rightleftharpoons 2HCl(g)
H
2
(
g
)
+
C
l
2
(
g
)
⇌
2
H
C
l
(
g
)
Which of the following statement is true?
Le Chatelier's Principle
Which of the following changes would allow the formation of more CrCI
3
? Assume the system is at equilibrium before these changes are done.
4
C
r
(
s
)
+
3
C
C
l
4
(
g
)
⇌
4
C
r
C
l
3
(
g
)
+
3
C
(
s
)
Δ
H
=
26.9
k
J
4Cr(s)+3CCl_4 (g)\rightleftharpoons4CrCl_3 (g)+3C(s)\qquad ΔH = 26.9 kJ
4
C
r
(
s
)
+
3
C
C
l
4
(
g
)
⇌
4
C
r
C
l
3
(
g
)
+
3
C
(
s
)
Δ
H
=
26.9
k
J
Le Chatelier's Principle
For the equilibrium process 2 NO (g) ⇌ N
2
(g) + O
2
(g), K
c
= 2.1x10
30
at 20
o
C and ΔH
o
= -413 kJ/mol. If O2 is injected into the mixture at equilibrium in a sealed rigid vessel, which of the following changes will occur?
Le Chatelier's Principle
For the equilibrium process 2 BrCl (g) ⇌ Br
2
(g) + Cl
2
(g), which of the following changes will cause additional Cl2 to be formed.
1. Addition of Br
2
ii. Addition of BrCl
For the following reaction at equilibrium, list three ways other than concentration to shift the reaction to favor the formation of products?
2
N
O
B
r
(
g
)
⇌
2
N
O
(
g
)
+
B
r
2
(
g
)
Δ
H
o
r
x
n
=
30
K
J
/
m
o
l
2NOBr(g)\rightleftharpoons 2NO(g) +Br_2(g) \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \Delta H^orxn=30KJ/mol
2
N
O
B
r
(
g
)
⇌
2
N
O
(
g
)
+
B
r
2
(
g
)
Δ
H
o
r
x
n
=
30
K
J
/
m
o
l
Le Chatelier's Principle
Determine the shift in equilibrium when the following changes are introduced to the following equilibrium:
(
N
H
4
)
(
H
2
N
C
O
2
)
(
S
)
⇌
2
N
H
3
(
g
)
+
C
O
2
(
g
)
(NH_4)(H_2NCO_2)(S) \rightleftharpoons 2NH_3(g)+CO_2(g)
(
N
H
4
)
(
H
2
N
C
O
2
)
(
S
)
⇌
2
N
H
3
(
g
)
+
C
O
2
(
g
)
Volume of the container is expanded by 10 L.
Le Chatelier's Principle
Consider the information provided in the table on the right for the following reaction:
H
2
(
g
)
+
C
l
2
(
g
)
⇌
2
H
C
l
(
g
)
H_2(g) +Cl_2(g)\rightleftharpoons 2HCl(g)
H
2
(
g
)
+
C
l
2
(
g
)
⇌
2
H
C
l
(
g
)
Which of the following statement is true?
Le Chatelier's Principle
Which ONE of the following changes will, at least in principle, increase the amount of C
6
H
12
O
6
(s) at equilibrium in the reaction:
6 CO
2
(g) + 6 H
2
O (l)
⇌
C
6
H
12
O
6
(s) + 6 O
2
(g) ΔH
o
is positive in the forward direction
Le Chatelier's Principle
Which of the following changes would allow the formation of more CrCI
3
? Assume the system is at equilibrium before these changes are done.
The equation for the reaction is:
Cr2O
3
(s)+3CCl
4
(l) ⇌ 2
CrCl
3
(s)+3
COCl
2
(g)
One of the demonstrations in this course was about the effect of temperature in chemical equilibrium. NO
2
(a brown gas) was kept in a flask in equilibrium with N
2
O
4
(a colourless gas). When the flask was immersed in liquid nitrogen, the mixture inside became colourless. On the other hand, when the flask was immersed in hot water, the mixture inside was brown. What can you say about the equilibrium: N
2
O4 (g)
⇌
2 NO
2
(g) from these observations?
Le Chatelier's Principle
Consider the equilibrium 4 NH
3
(g) + 5 O
2
(g)
⇌
4 NO (g) + 6H
2
O (g). Which one of the following statements correctly describes what happens when the described change is made in the reaction vessel? Interpret the arrow symbol → to mean “has the result that … “
Le Chatelier's Principle
For the process: 2 ICl (s)
⇌
I
2
(s) + Cl
2
(g)
At equilibrium, which of the following changes will cause additional Cl
2
to be formed?
Le Chatelier's Principle
For the equilibrium process 2 NO (g) = N
2
(g) + O
2
(g), Kc = 2.1x10
30
at 20
o
C and ΔH
o
= -413 kJ/mol. If the temperature of a mixture at equilibrium is increased from 20
o
C to 30
o
C, which of the following will occur?
Which of the following statement is correct
Which of the following equilibrium will not respond to a change in container volume?
Le Chatelier's Principle
In an esterification reaction, a carboxylic acid and an alcohol react to form an ester and water. This reaction establishes an equilibrium because the reverse process can also occur. If the water is allowed to boil and leave the system as water vapour, how will the equilibrium respond?
The Haber-Bosch process is the process used to produce industrial quantities of ammonia, most of which is used to make fertilizer.
N
2
(
g
)
+
3
H
2
(
g
)
⇌
2
N
H
3
(
g
)
N_{2(g)}+3\ H_{2(g)}\rightleftharpoons 2\ NH_{3(g)}
N
2
(
g
)
+
3
H
2
(
g
)
⇌
2
N
H
3
(
g
)
The equilibrium shifts left when,
(Duplicated)
For the following reaction predict the change in K when a catalyst is added.
(Duplicated)
For the following reaction predict the direction the equilibrium will shift when the total pressure
is decreased?
(Duplicated)
For the following reaction predict the direction the equilibrium will shift when steam is added to the reaction?
(Duplicated)
For the following reaction predict the change in K when the temperature is increased?
(Duplicated)
For the following reaction predict the direction the equilibrium will shift when CO
2
is selectively removed?
For the following reaction predict the direction the equilibrium will shift when the pressure of O
2
is increased?
Le Chatelier's Principle
Of the following equilibria, only ______ will shift to the left in response to a decrease in volume.
The reaction below is at equilibrium. You want to apply Le Chatelier’s principle to produce a higher quantity of product gases. Which change will accomplish this effect?
CO
2
(g) + 2 H
2
O (l)
⇌
CH
4
(g) + 2 O
2
(g)
For the equilibrium process 2 NO (g)
⇌
N
2
(g) + O
2
(g), K
c
= 2.1x10
30
at 20
o
C and ΔH
o
= -413 kJ/mol. If O
2
is injected into the mixture at equilibrium in a sealed rigid vessel, which of the following changes will occur?
Le Chatelier's Principle
For the equilibrium process 2 BrCl (g)
⇌
Br
2
(g) + Cl
2
(g), which of the following changes will cause additional Cl
2
to be formed.
1. Addition of Br
2
2. Addition of BrCl
Le Chatelier's Principle
For the equilibrium process 2 NO (g) = N
2
(g) + O
2
(g), K
c
= 2.1x10
30
at 20
o
C and ΔH
o
= -413 kJ/mol. If the temperature of a mixture at equilibrium is increased from 20
o
C to 30
o
C, which of the following will occur?
Le Chatelier's Principle
Which of the following changes would allow the formation of more CrCI
3
? Assume the system is at equilibrium before these changes are done.
Le Chatelier's Principle: Percent dissociation
A solution made by dissolving 0.1 mol of acetic acid in 1.0 L of water is 4.1% dissociated. Which of the modifications below would cause the % dissociation of the acetic acid in the container to
increase
? (Ka for acetic acid is 1.8×10
-5
.)
Which of the changes below would result in a shift towards the products if applied to this system at equilibrium?
C
O
2
(
g
)
+
C
(
g
r
a
p
h
i
t
e
)
⇌
2
C
O
(
g
)
CO_2 (g)+C(graphite)⇌2CO(g)
C
O
2
(
g
)
+
C
(
g
r
a
p
hi
t
e
)
⇌
2
C
O
(
g
)
Le Chatelier's Principle
How many of these reactions will shift towards the products, if the size of the reaction container is decreased after equilibrium has been reached?
Le Chatelier's Principle
For the reaction of barium carbonate shown here, which of these changes suggested below will result in a decrease in pH at equilibrium? Assume that the reaction is at equilibrium before making any change, and that there is excess BaCO
3
and H
2
O present.
B
a
C
O
3
(
s
)
+
2
H
+
(
a
q
)
⇌
B
a
2
+
(
a
q
)
+
C
O
2
(
g
)
+
H
2
O
(
l
)
BaCO_3 (s)+2H^+ (aq)⇌Ba^{2+} (aq)+CO_2 (g)+H_2 O(l)
B
a
C
O
3
(
s
)
+
2
H
+
(
a
q
)
⇌
B
a
2
+
(
a
q
)
+
C
O
2
(
g
)
+
H
2
O
(
l
)
Le Chatelier's Principle
Use the following reaction scenario to answer the following questions
S
O
2
(
g
)
+
C
ℓ
2
(
g
)
⇌
S
O
2
C
ℓ
2
(
g
)
Δ
r
H
°
<
0
SO_2(g)+Cℓ_2(g)⇌SO_2Cℓ_2(g)\qquadΔ_rH°<0
S
O
2
(
g
)
+
C
ℓ
2
(
g
)
⇌
S
O
2
C
ℓ
2
(
g
)
Δ
r
H
°
<
0
You have prepared a container with these compounds and allowed it to come to equilibrium. You now have a choice of different ways to modify your system at equilibrium. Assume that during each of these changes, all other parameters remain constant. Select all that apply.
For the reaction
X
+
Y
⇌
2
Z
X+Y \rightleftharpoons2Z
X
+
Y
⇌
2
Z
, a system at equilibrium is initially prepared. The equilibrium concentrations are given by the following bar chart:
If half of the amount of Z is removed from the system, which of the following bar charts represents the concentrations in the system when it returns to equilibrium?
Over time, quicklime (calcium oxide) reacts with carbon dioxide in the air to produce calcium carbonate, as shown here:
C
a
O
(
s
)
+
C
O
2
(
g
)
⇌
C
a
C
O
3
(
s
)
CaO(s)+ CO_2(g)⇌ CaCO_3(s)
C
a
O
(
s
)
+
C
O
2
(
g
)
⇌
C
a
C
O
3
(
s
)
Suppose that you want to increase the yield of CaCO
3
(
s
) produced
by shifting the equilibrium
towards the products
. Which of these suggested changes would accomplish this? Select all that apply
Which of the following reactions will shift towards the
products
if the size of the reaction container is
increased
after equilibrium was reached? Select all that apply.
Use the following information for
both
of the next two questions
We can easily observe shifts in the equilibrium of the following reaction because the reactants and products have different colours.
2
N
O
2
(
g
)
⇌
N
2
O
4
(
g
)
D
a
r
k
r
e
d
C
o
l
o
u
r
l
e
s
s
\def\arraystretch{1.5} \begin{array}{ccc} &2NO_2(g)&⇌&N_2O_4(g) \\ &\rm Dark \ red && \rm Colourless \end{array}
2
N
O
2
(
g
)
Dark
red
⇌
N
2
O
4
(
g
)
Colourless
Consider the endothermic reaction:
N
H
4
C
l
(
s
)
⇌
N
H
4
+
(
a
q
)
+
C
l
−
(
a
q
)
NH_4Cl(s)\rightleftharpoons NH_4^+(aq)+Cl^-(aq)
N
H
4
C
l
(
s
)
⇌
N
H
4
+
(
a
q
)
+
C
l
−
(
a
q
)
. Which of the following does
not
occur when the reaction temperature is decreased?
Suppose you know that the reaction
A
⇌
B
A \rightleftharpoons B
A
⇌
B
is endothermic. What happens to the rates of the forward and reverse reactions when the reaction temperature is increased?
Le Chatelier's Principle: Exothermic Reaction
Carbon disulfide, CS
2
, and chlorine gas react according to the following exothermic equilibrium reaction:
C
S
2
(
g
)
+
3
C
l
2
(
g
)
⇌
S
2
C
l
2
(
g
)
+
C
C
l
4
(
g
)
CS_2 (g)+3Cl_2 (g)⇌S_2 Cl_2 (g)+CCl_4 (g)
C
S
2
(
g
)
+
3
C
l
2
(
g
)
⇌
S
2
C
l
2
(
g
)
+
C
C
l
4
(
g
)
If a vessel containing a mixture of these compounds starts at equilibrium and is exposed to a change, which of the following statements is TRUE?
Le Chatelier's Principle
Over time, quicklime (calcium oxide) reacts with carbon dioxide in the air to produce calcium carbonate, as shown here:
C
a
O
(
s
)
+
C
O
2
(
g
)
⇌
C
a
C
O
3
(
s
)
CaO(s) + CO_2(g) ⇌ CaCO_3(s)
C
a
O
(
s
)
+
C
O
2
(
g
)
⇌
C
a
C
O
3
(
s
)
Suppose that you want to increase the yield of CaCO
3
(s) produced by shifting the equilibrium towards the products. Which of these suggested changes would accomplish this?