CHEM 131 - ADVANCED GENERAL CHEMISTRY I Le Chatelier's Principle Question Bank Set 3

CHEM 131 - ADVANCED GENERAL

CHEMISTRY I - Le Chatelier’s

Principle

Question Bank - Set 3

Liberty University

Question 1

Question

Consider the equilibrium reaction:

2SO2(g)+O2(g)⇌2SO3(g)

If the pressure is increased by decreasing the volume of the reaction con-

tainer, predict the direction in which the equilibrium will shift according to Le

Chatelier’s Principle. Justify your answer.

Solution

Step 1: When the pressure is increased by decreasing the volume of the reaction

container, the system will attempt to decrease the pressure by favoring the

reaction that produces fewer gas molecules.

Step 2: In this reaction, 3 molecules of gas are on the left side (2 SO2 and

1 O2), while 2 molecules of gas are on the right side (2 SO3).

Step 3: Thus, to decrease the pressure, the equilibrium will shift to the right,

towards the side with fewer gas molecules.

Step 4: This means that more SO3 will be formed at equilibrium, reducing

the pressure in the system.

Therefore, when the pressure is increased by decreasing the volume of the

reaction container, the equilibrium will shift to the right (towards the formation

of more SO3).

Question 2

Question

Consider the reaction:

2A(g) + B(g)⇌3C(g)

Suppose the reaction is at equilibrium at a certain temperature. If the pres-

sure of the system is increased by decreasing the volume of the container, pre-

dict the direction in which the equilibrium will shift according to Le Chatelier’s

Principle. Justify your answer.

Solution

Step 1: When the pressure of a system at equilibrium is increased by decreasing

the volume of the container, the system will shift to reduce the pressure. Step 2:

Since the total number of moles of gas on the left side of the reaction (2A(g) +

B(g)) is greater than on the right side (3C(g)), decreasing the volume will cause

the system to shift in the direction that consumes gas molecules. Step 3: As a

result, the equilibrium will shift to the right to decrease the total pressure by

favoring the formation of product, 3C(g).

Question 3

Question

Consider the following equilibrium reaction:

2 NOBr(g) ⇌2 NO(g) + Br2(g)

If the concentration of NOBr is increased, predict the direction in which the

equilibrium will shift according to Le Chatelier’s Principle. Justify your answer.

Solution

Step 1: Le Chatelier’s Principle states that if a system at equilibrium is sub-

jected to a stress (such as a change in concentration, pressure, or temperature),

the system will adjust in order to counteract the stress.

Step 2: In this case, if the concentration of NOBr is increased, the system

will shift in the direction that consumes NOBr in order to decrease the ex-

cess concentration. This means the system will shift to the right, favoring the

formation of products (NO and Br2).

Step 3: The equilibrium reaction can be represented as:

2 NOBr(g) ⇌2 NO(g) + Br2(g)

Step 4: When the concentration of NOBr is increased, the system will shift

to the right to consume the excess NOBr. This will result in an increase in the

concentrations of NO and Br2, favoring the formation of products.

Step 5: Therefore, the equilibrium will shift to the right when the concen-

tration of NOBr is increased, according to Le Chatelier’s Principle.

Question 4

Question

Consider the following equilibrium reaction:

H2O(g) ⇌H2O(l)

If the temperature of the system is increased, predict how Le Chatelier’s

Principle will affect the equilibrium position and justify your answer.

Solution

Step 1: When the temperature of the system is increased, the equilibrium will

shift in the direction that absorbs heat.

Step 2: In this case, the forward reaction (from gas to liquid) is endothermic

since it absorbs heat to break intermolecular forces and increase disorder. Thus,

an increase in temperature will favor the endothermic forward reaction to absorb

the additional heat.

Step 3: As a result, the equilibrium position will shift to the right, favoring

the formation of more liquid water molecules.

Step 4: Therefore, according to Le Chatelier’s Principle, increasing the tem-

perature will cause the equilibrium position to shift towards the formation of

more liquid water molecules.

Question 5

Question

Consider the following equilibrium reaction:

2 SO2(g)+O2(g)⇌2 SO3(g)

At a certain temperature, the equilibrium constant, K, for the reaction above

is 50. If a student adds a catalyst to the reaction vessel, which of the following

changes will occur to the system (increase, decrease, or remain unchanged): the

concentration of SO3, the concentration of SO2, the concentration of O2, and

the value of the equilibrium constant, K? Justify your answer.

Solution

Le Chatelier’s Principle states that if a system at equilibrium is subjected to a

change, the system will adjust to counteract that change and establish a new

equilibrium. In this case, we are adding a catalyst to the system, so let’s analyze

the potential changes:

Step 1: Concentration of SO Adding a catalyst does not affect the con-

centrations of the reactants or products in the equilibrium mixture. Therefore,

the concentration of SO3will remain unchanged.

Step 2: Concentration of SO The addition of a catalyst does not change

the concentrations of reactants or products in the equilibrium mixture. Hence,

the concentration of SO2will not be affected.

Step 3: Concentration of O Similar to the concentrations of SO3and

SO2, the concentration of O2will also remain unchanged with the addition of a

catalyst.

Step 4: Equilibrium Constant, K The equilibrium constant, K, is a

constant value at a given temperature. It is not affected by changes in concen-

tration or the addition of a catalyst. Therefore, the value of the equilibrium

constant, K, will remain unchanged.

In conclusion, adding a catalyst to the reaction vessel will not affect the con-

centrations of SO3, SO2, or O2, andthevalueof theequilibriumconstant, K, willalsoremainunchanged.

Question 6

Question

Consider the following reaction at equilibrium:

2 SO2(g)+O2(g)⇌2 SO3(g)

If the pressure of the system is increased, predict the direction in which the

equilibrium will shift according to Le Chatelier’s Principle.

Solution

To predict the direction in which the equilibrium will shift when the pressure

of the system is increased, we need to consider the effects of pressure on the

system.

Step 1: Identify the effects of increasing pressure on the system. When

the pressure of a system is increased, the system will shift in the direction that

reduces the total number of moles of gas to decrease the pressure.

Step 2: Determine the changes in the number of moles of gas on both sides

of the reaction. On the reactant side, there are 3 moles of gas (2 moles of SO2

and 1 mole of O2), and on the product side, there are 2 moles of gas (SO3).

Step 3: Predict the direction of the equilibrium shift. Since the total num-

ber of moles of gas on the product side is less than that on the reactant side,

increasing the pressure will cause the equilibrium to shift in the direction that

decreases the total number of moles of gas. Therefore, the equilibrium will shift

to the left, favoring the formation of reactants SO2and O2and reducing the

pressure.

Therefore, according to Le Chatelier’s Principle, if the pressure of the system

is increased, the equilibrium will shift to the left.

Question 7

Question

Consider the following equilibrium reaction involving gases:

2SO2(g)+O2(g)⇌2SO3(g)

If the temperature of the system is increased, predict the direction in which

the equilibrium will shift according to Le Chatelier’s Principle. Justify your

answer.

Solution

Step 1: According to Le Chatelier’s Principle, when a system at equilibrium is

disturbed by a change in conditions (such as temperature, pressure, or concen-

tration), the equilibrium will shift in a way that counteracts the change.

Step 2: In this case, if the temperature is increased, the system will respond

by trying to decrease the temperature.

Step 3: Increasing the temperature of an endothermic reaction (where heat

is a reactant) will favor the reaction that absorbs heat.

Step 4: The forward reaction in this equilibrium is endothermic (since it

absorbs heat), meaning it requires heat to form the products.

Step 5: Therefore, if the temperature is increased, the equilibrium will shift

to the right (the forward reaction) in order to consume the added heat.

Step 6: Thus, the equilibrium will shift towards the formation of more SO3,

with an overall increase in the concentration of SO3gas.

Question 8

Question

Consider the following reaction at equilibrium:

2A(g) + B(g)⇌C(g)

If the pressure is increased in the system by decreasing the volume, predict

the direction in which the equilibrium will shift according to Le Chatelier’s

Principle. Justify your answer with an explanation.

Solution

Step 1: According to Le Chatelier’s Principle, when a system at equilibrium is

subjected to a change in concentration, temperature, or pressure, the system

will adjust to counteract the change and restore equilibrium.

Step 2: In this case, increasing the pressure by decreasing the volume of the

system will cause the system to shift in the direction that decreases the total

number of gas molecules. This is because by reducing the volume, the pressure

is increased, and the system will shift to the side with fewer moles of gas to

reduce the pressure.

Step 3: In the given reaction, 2 moles of A and 1 mole of B combine to form

1 mole of C. Therefore, the total number of moles on the left side is 3 (2 moles

of A + 1 mole of B) while on the right side it is 1 mole of C.

Step 4: To decrease the total number of moles of gas and relieve the increase

in pressure, the equilibrium will shift to the left, favoring the reactants. This

means more A and B will react to form more C until a new equilibrium is

established.

Step 5: In conclusion, when the pressure is increased by decreasing the

volume, the equilibrium will shift to the left to reduce the total number of gas

molecules and alleviate the pressure increase.

Question 9

Question

Consider the following equilibrium reaction:

2A(g) + B(g) ⇌3C(g) + D(g)

If the temperature of the system is increased, predict the direction in which

the equilibrium will shift according to Le Chatelier’s Principle. Justify your

answer.

Solution

Step 1: When the temperature of a system at equilibrium is changed, the system

will respond in a way that tends to counteract that change. Step 2: In this case,

increasing the temperature will favor the endothermic direction of the reaction

(the direction that absorbs heat). Step 3: The endothermic direction is the

direction that consumes heat, which means it favors the reactants. Step 4:

Therefore, the equilibrium will shift to the left, favoring the formation of A and

B. Step 5: This shift to the left will result in an increase in the concentrations

of A and B, while decreasing the concentrations of C and D. Step 6: Thus, the

equilibrium will shift towards the reactants (A and B) in order to consume the

added heat.

Question 10

Question

Consider the reaction:

2H2O(g)⇌2H2(g)+O2(g)

If we increase the pressure of the system by decreasing the volume of the

container, predict the effect on the concentration of each species in the system

according to Le Chatelier’s Principle.

Solution

Let’s analyze the effect of increasing the pressure on the system described by

the reaction:

2H2O(g)⇌2H2(g)+O2(g)

Step 1: Identify the stoichiometry of the reaction.

The stoichiometry of the reaction is balanced as follows:

2H2O(g)⇌2H2(g)+O2(g)

This reaction shows that two moles of water can produce two moles of hy-

drogen and one mole of oxygen.

Step 2: Determine the change in volume on the forward and reverse reac-

tions.

When the volume is decreased (pressure is increased), the system will want

to counteract this change by shifting its position of equilibrium. This can be

seen in the reaction equation by the unequal number of moles on the left and

right sides.

Step 3: Apply Le Chatelier’s Principle.

Since there are more moles of gas on the right side of the reaction, the system

will shift to the side with fewer moles of gas, which is the left side:

2H2O(g)⇌2H2(g)+O2(g)

Therefore, by increasing the pressure (decreasing the volume), the concen-

tration of water vapor will increase, while the concentrations of hydrogen gas

and oxygen gas will decrease.

This shift helps to alleviate the increase in pressure by reducing the total

number of gas molecules present in the system.

Question 11

Question

Consider the following equilibrium reaction at a certain temperature:

2 SO2(g)+O2(g)⇌2 SO3(g)

If the reaction vessel is initially at equilibrium and then the volume of the

vessel is suddenly decreased, predict the direction in which the equilibrium will

shift and explain why.

Solution

Step 1: When the volume of the vessel is suddenly decreased, the pressure inside

the vessel will increase.

Step 2: According to Le Chatelier’s Principle, a system at equilibrium will

shift in such a way as to counteract the change imposed on it.

Step 3: In this case, since the decrease in volume leads to an increase in

pressure, the equilibrium will shift in the direction that reduces the total number

of gas moles in order to lower the pressure.

Step 4: The side of the reaction that has fewer moles of gas is the side with

3 moles of gas (2 SO2 + O2).

Step 5: Therefore, the equilibrium will shift to the left, favoring the forma-

tion of SO2 and O2, in order to reduce the total number of gas moles and lower

the pressure inside the vessel.

Question 12

Question

Consider the reaction:

N2O4(g)⇌2NO2(g)

If the volume of the container is increased at constant temperature, predict

the direction of the shift in equilibrium and explain your reasoning using Le

Chatelier’s Principle.

Solution

To determine the effect of increasing the volume of the container on the equilib-

rium of the given reaction, we will apply Le Chatelier’s Principle which states

that if a system at equilibrium is disturbed by changing the conditions, the

system will adjust to counteract that change and restore a new equilibrium

state.

Step 1: Write the reaction The given reaction is:

N2O4(g)⇌2NO2(g)

Step 2: Determine the effect of increasing volume Increasing the

volume of the container will decrease the pressure inside. According to Le

Chatelier’s Principle, the system will shift in the direction that produces more

moles of gas to increase the pressure.

Step 3: Analyze the moles of gas on each side On the reactant side

(N2O4(g)), there is 1 mole of gas. On the product side (2NO2(g)), there are 2

moles of gas.

Step 4: Predict the direction of the shift Since increasing the volume

decreases the pressure, the system will shift to the side with more moles of gas

to increase the pressure. Therefore, the equilibrium will shift to the right to

produce more gaseous moles of NO2.

Therefore, when the volume of the container is increased at constant tem-

perature, the equilibrium will shift to the right to produce more NO2(g).

Question 13

Question

A reaction system is at equilibrium with the following reaction:

2 SO2(g)+ O2(g)⇌2 SO3(g)

If the pressure of the system is increased by decreasing the volume, predict

the direction in which the system will shift to regain equilibrium according to

Le Chatelier’s Principle.

Solution

1. When the pressure of the system is increased by decreasing the volume,

according to Le Chatelier’s Principle, the system will shift in the direction that

reduces the total number of moles of gas to relieve the pressure increase.

2. In this reaction, the total number of moles of gas on the left side of the

reaction is 3 (2 moles of SO and 1 mole of O), while on the right side it is 2

moles of SO.

3. Therefore, to reduce the total number of moles of gas, the system will

shift to the side with fewer moles of gas, which is the right side of the reaction.

4. The equilibrium will shift to the right, favoring the formation of more SO

gas molecules.

Hence, the system will shift towards the right in order to regain equilibrium

when the pressure is increased by decreasing the volume.

Question 14

Question

Consider the following reaction:

2 SO2(g)+O2(g)⇌2 SO3(g)

If the concentration of SO2is increased at constant temperature and pres-

sure, predict the direction in which the equilibrium will shift according to Le

Chatelier’s Principle. Justify your answer.

Solution

Step 1: Le Chatelier’s Principle states that when a system at equilibrium is

disturbed, the system will shift to counteract the disturbance.

Step 2: If the concentration of SO2is increased, the system will shift to

counteract this increase by consuming some of the additional SO2.

Step 3: To do this, the equilibrium position will shift to the right, favoring

the forward reaction.

Step 4: This means that the concentration of SO3will increase while the

concentrations of SO2and O2will decrease.

Step 5: Therefore, the direction in which the equilibrium will shift when

the concentration of SO2is increased at constant temperature and pressure is

towards the products.

Question 15

Question

Consider the reversible reaction:

N2O4(g)⇌2NO2(g)

If the temperature of the system is increased, predict the effect on the equi-

librium position of the reaction according to Le Chatelier’s Principle. Justify

your answer.

Solution

To determine the effect of increasing temperature on the equilibrium position

of the reaction, we need to consider the reaction’s enthalpy change (∆H).



If the reaction is exothermic (∆H < 0), increasing the temperature will

shift the equilibrium position in the direction that absorbs heat.



If the reaction is endothermic (∆H > 0), increasing the temperature will

shift the equilibrium position in the direction that releases heat.

Since the reaction N2O4(g)⇌2NO2(g) is endothermic with a positive en-

thalpy change, increasing the temperature will shift the equilibrium position in

the direction that absorbs heat. This means that the equilibrium will shift to

the right, favoring the formation of more NO2(g) at the expense of N2O4(g).

Therefore, according to Le Chatelier’s Principle, increasing the temperature

will cause the equilibrium position to shift towards the products, increasing the

concentration of NO2and decreasing the concentration of N2O4at equilibrium.

Question 16

Question

Consider the following equilibrium reaction:

N2(g) + 3H2(g) ⇌2NH3(g)

If the pressure on the reaction mixture is increased by decreasing the vol-

ume of the container, predict the direction in which the equilibrium will shift

according to Le Chatelier’s Principle. Justify your answer using equilibrium

principles.

Solution

Step 1: Identify the effect of increasing pressure on the system. When the

pressure is increased by decreasing the volume of the container, the system will

try to decrease the pressure by favoring the side of the reaction with fewer moles

of gas.

Step 2: Determine the total number of moles of gas on each side of the

reaction. On the left side: 1 mole of N2 gas and 3 moles of H2 gas, totaling 4

moles of gas. On the right side: 2 moles of NH3 gas.

Step 3: Compare the total moles of gas on each side. Since the left side has

4 moles of gas while the right side has 2 moles of gas, decreasing the volume

of the container will cause the equilibrium to shift to the right to decrease the

total number of gas moles and alleviate the increase in pressure.

Therefore, according to Le Chatelier’s Principle, the equilibrium will shift to

the right to favor the formation of more NH3 gas molecules when the pressure

is increased by decreasing the volume of the container.

Question 17

Question

Consider the equilibrium reaction:

H2O(g)⇌H2O(l)

If the pressure on the system is increased, predict the direction in which the

equilibrium will shift according to Le Chatelier’s Principle.

Solution

Le Chatelier’s Principle states that if a stress is applied to a system at equi-

librium, the system will adjust itself in order to counteract the effect of the

stress.

Step 1: When the pressure on the system is increased, the system will shift

to the side with fewer gas molecules in order to decrease the pressure.

In this reaction, there is 1 molecule of gas on the left side and 0 molecules

of gas on the right side. Therefore, increasing the pressure will cause the equi-

librium to shift to the right (towards the liquid phase) to reduce the pressure.

Therefore, the equilibrium will shift to the right (towards the liquid phase)

when the pressure on the system is increased.

Question 18

Question

Consider the following equilibrium reaction:

H2O(g) ⇌H2O(l)

If the temperature of the system is increased, predict how the position of

equilibrium will shift according to Le Chatelier’s Principle. Justify your answer

with a detailed explanation.

Solution

To determine how the position of equilibrium will shift when the temperature

of the system is increased, we must consider the effects of this change on the

forward and reverse reactions.

Step 1: When the temperature is increased, the system will respond in a

way that absorbs heat. In an endothermic reaction like the one given, heat

is a reactant. Therefore, increasing the temperature will shift the equilibrium

position in the direction that consumes heat, which is the forward reaction.

Step 2: By shifting towards the forward reaction, the concentration of water

vapor (H2O(g)) will decrease, while the concentration of liquid water (H2O(l))

will increase. This shift is consistent with Le Chatelier’s Principle, which states

that a system at equilibrium will adjust to counteract any imposed change.

Step 3: In summary, increasing the temperature of the system will cause

the equilibrium position to shift towards the formation of liquid water (H2O(l)).

This predicts an increase in the concentration of liquid water and a decrease in

the concentration of water vapor.

Question 19

Question

Consider the following reaction at equilibrium:

N2(g) + 3H2(g)⇌2NH3(g)

What will happen to the equilibrium position if the volume of the container

is decreased? Explain your answer based on Le Chatelier’s Principle.

Solution

Step 1: According to Le Chatelier’s Principle, when a system at equilibrium

is subjected to a change, the system will adjust to counteract that change and

establish a new equilibrium position.

Step 2: If the volume of the container is decreased, the system will try to

reduce the pressure to counteract this change. Since there are 4 moles of gas

on the left side of the reaction and only 2 moles on the right side, reducing the

volume will cause the reaction to shift towards the side with fewer moles of gas

to decrease the pressure.

Step 3: Therefore, in this case, the equilibrium position will shift to the

right to produce more ammonia gas (NH3) molecules. This will increase the

total moles of gas in order to counteract the decrease in volume and pressure.

Step 4: As a result, the concentration of NH3will increase while the con-

centrations of N2and H2will decrease to establish a new equilibrium position

with a higher concentration of NH3.

Step 5: In conclusion, by reducing the volume of the container, the equilib-

rium position of the reaction will shift to the right to increase the concentration

of ammonia gas according to Le Chatelier’s Principle.

Question 20

Question

Consider the following reaction at equilibrium:

2NOCl(g)⇌2NO(g) + Cl2(g)

If the pressure of the system is increased, predict the shift in equilibrium

according to Le Chatelier’s Principle. Justify your answer.

Solution

Step 1: **Identify the Effect of Increased Pressure** When the pressure of a

gaseous system is increased, the system will shift towards the side with fewer

moles of gas molecules to reduce the pressure.

Step 2: **Determine the Change in the Number of Moles** Let’s compare

the number of gas moles on each side of the reaction: - Left side: 1 mole of

NOCl - Right side: 2 moles of NO + 1 mole of Cl

There are a total of 3 moles of gas on the right side, which is greater than

the 1 mole of gas on the left side.

Step 3: **Predict the Shift in Equilibrium** Since the right side has more

moles of gas than the left side, increasing the pressure will shift the equilibrium

to the left to decrease the total number of gas moles.

Therefore, the system will shift to the left to produce more NOCl, consuming

some NO and Cl in the process.

In summary, increasing the pressure will cause the equilibrium to shift to the

left to reduce the total number of gas moles and alleviate the pressure increase.

Question 21

Question

Consider the reaction:

2 NOCl(g)⇌2 NO(g) + Cl2(g)

If the volume of the container is decreased by half at constant temperature,

predict the direction in which the equilibrium will shift. Justify your answer

using Le Chatelier’s Principle.

Solution

Step 1: Identify the reaction. The reaction given is the decomposition of NOCl

into NO and Cl2.

Step 2: Identify the effect of decreasing the volume. When the volume of

the container is decreased, the pressure inside the container increases.

Step 3: Apply Le Chatelier’s Principle. According to Le Chatelier’s Princi-

ple, when a stress is applied to a system at equilibrium, the system responds by

shifting the equilibrium in a direction that helps to alleviate the stress.

Step 4: Predict the direction of the shift. In this case, decreasing the vol-

ume increases the pressure inside the container. According to Le Chatelier’s

Principle, the system will respond by shifting the equilibrium in the direction

that reduces the pressure. Since there are 3 moles of gas on the left side of the

reaction and only 3 moles on the right side, changing the volume will not shift

the equilibrium towards products or reactants based on the change in moles of

gas.

Step 5: Conclusion. Therefore, when the volume of the container is decreased

by half at constant temperature, the equilibrium will not shift in a particular

direction based solely on the change in volume. The system will adjust to

maintain the equilibrium position without favoring the formation of products

or reactants.

Question 22

Question

Consider the following equilibrium reaction:

2SO2(g)+O2(g)⇌2SO3(g)

If the temperature of the system is increased, explain how Le Chatelier’s

Principle predicts the shift in equilibrium and the reasoning behind it.

Solution

Le Chatelier’s Principle states that if a stress is applied to a system at equilib-

rium, the system will shift in a way that minimizes the effect of that stress. In

this case, we are increasing the temperature of the system.

Step 1: According to Le Chatelier’s Principle, increasing the temperature

of an exothermic reaction will cause the equilibrium position to shift to the left

in order to consume the excess heat. This is because the reaction is favoring the

side of the reaction that absorbs heat to counteract the increase in temperature.

Therefore, for the given reaction:

2SO2(g)+O2(g)⇌2SO3(g)

If the temperature of the system is increased, the equilibrium will shift to

the left (toward the reactants) in order to absorb the excess heat.

Therefore, the equilibrium position will shift towards more SO2(g)andO2(g)andlessSO3(g)inordertocounteracttheincreaseintemperature.

Question 23

Question

Consider the following reaction at equilibrium:

N2O4(g)⇌2NO2(g)

If the concentration of N2O4is increased at constant temperature, predict

how the equilibrium will shift. Justify your answer using Le Chatelier’s Princi-

ple.

Solution

Step 1: Writing the reaction quotient Given reaction:

N2O4(g)⇌2NO2(g)

The equilibrium constant expression is:

K=[NO2]2

[N2O4]

Step 2: Analyzing the effect of increasing N2O4If the concentration of N2O4

is increased, the equilibrium will shift to the right to counteract this change.

According to Le Chatelier’s Principle, the system will try to reduce the ex-

cess N2O4by favoring the forward reaction to produce more NO2until a new

equilibrium is established.

Step 3: Justifying the equilibrium shift Increasing the concentration of N2O4

means the ratio of [N2O4] in the reaction quotient will increase. To balance the

equilibrium, the reaction will shift to the right, favoring the forward reaction,

until the equilibrium constant expression is satisfied again. This shift towards

the production of more NO2helps consume the excess N2O4.

Therefore, by increasing the concentration of N2O4, the equilibrium will shift

to the right to produce more NO2.

Question 24

Question

Consider the following reaction at equilibrium in a closed system:

2SO2(g)+O2(g)⇌2SO3(g)

If the pressure of the system is increased by reducing the volume, predict

the direction in which the equilibrium will shift according to Le Chatelier’s

Principle. Justify your answer.

Solution

Step 1: According to Le Chatelier’s Principle, when a stress is applied to a

system at equilibrium, the system will shift in a way that counteracts the stress

to reach a new equilibrium.

Step 2: When the pressure is increased by reducing the volume, the system

will shift in the direction that decreases the total number of moles of gas to

counteract the increased pressure.

Step 3: In this reaction, the total number of moles of gas on the left side is

3 (2 moles of SO2and 1 mole of O2), while on the right side it is 2 (2 moles of

SO3).

Step 4: To decrease the total number of moles of gas and counteract the

increased pressure, the equilibrium will shift to the side with fewer moles of gas.

Therefore, the reaction will shift to the left.

Step 5: The equilibrium shift to the left means that the concentrations of

SO2and O2will increase, while the concentration of SO3will decrease.

Question 25

Question

Consider the following reaction at equilibrium:

2CH3COOH ⇌CH3COO−+ H3O+

How will each of the following changes affect the equilibrium position (shift

to the right, shift to the left, or no shift)? Justify your answer in terms of Le

Chatelier’s Principle.

Change 1: Addition of more acetic acid (CH3COOH)

Change 2: Removal of some water (H2O)

Change 3: Increase in temperature

Change 4: Addition of a catalyst

Solution

Change 1: Addition of more acetic acid (CH3COOH)

Step 1: Adding more acetic acid will shift the equilibrium to the left. Ac-

cording to Le Chatelier’s Principle, if the concentration of a reactant is increased,

the equilibrium position will shift to the side that consumes that reactant. In

this case, adding more acetic acid will shift the equilibrium to the left to consume

the excess acetic acid added.

Change 2: Removal of some water (H2O)

Step 2: Removing some water will also shift the equilibrium to the left.

Since water is a product in this reaction, removing water will shift the equilib-

rium to the left to produce more water.

Change 3: Increase in temperature

Step 3: An increase in temperature will shift the equilibrium to the left. In

this reaction, the forward reaction is endothermic (heat-absorbing). According

to Le Chatelier’s Principle, increasing the temperature will favor the endother-

mic reaction to absorb the excess heat. Therefore, the equilibrium will shift to

the left to consume heat.

Change 4: Addition of a catalyst

Step 4: The addition of a catalyst does not affect the position of equilibrium.

A catalyst speeds up both the forward and reverse reactions equally, so the

equilibrium position will remain unchanged.

Question 26

Question

Consider the reaction:

2SO2(g)+O2(g)⇌2SO3(g)

If the volume of the container is decreased, predict the effect on the equilib-

rium position of the reaction and explain why.

Solution

To determine the effect of decreasing the volume of the container on the equilib-

rium position of the reaction 2SO2(g)+O2(g)⇌2SO3(g), we need to analyze

how the reaction responds to changes in pressure based on Le Chatelier’s Prin-

ciple.



If the volume of the container is decreased, the pressure inside the con-

tainer will increase.



According to Le Chatelier’s Principle, the system will respond in such a

way as to counteract the change.

Step 1: Determine which side of the reaction (reactants or products) has a

greater number of gas molecules.

In the reaction 2SO2(g) + O2(g)⇌2SO3(g): - 2 moles of SO2 - 1 mole of

O2 - 2 moles of SO3

The sum of the coefficients on the left side is 3 and the sum on the right

side is 4. Therefore, the products side (2SO3(g)) has a greater number of gas

molecules.

Step 2: Determine how the equilibrium will shift in response to an increase

in pressure.

Since the products side has more gas molecules, the equilibrium will shift

to the left (towards the reactants) to decrease the total pressure inside the

container.

Step 3: Conclusion

When the volume of the container is decreased, the equilibrium position of

the reaction 2SO2(g)+O2(g)⇌2SO3(g) will shift towards the left (reactants

side) in order to decrease the pressure inside the container.

Question 27

Question

Consider the following reaction at equilibrium:

2 SO2(g)+O2(g)⇌2 SO3(g)

Explain what would happen to the equilibrium position if the pressure of

the system is increased by decreasing the volume of the container. Justify your

answer with reference to Le Chatelier’s Principle.

Solution

Step 1: According to Le Chatelier’s Principle, if the pressure of a system at

equilibrium is increased by decreasing the volume, the system will shift in the

direction that reduces the pressure. This is because the system will respond to

alleviate the stress placed upon it.

Step 2: Let’s consider the reaction:

2 SO2(g)+O2(g)⇌2 SO3(g)

Step 3: Note that in this reaction, the total number of moles of gas on the

left side of the reaction (3 moles) is greater than the total number of moles of

gas on the right side (2 moles).

Step 4: When the volume is decreased (i.e., pressure is increased), the system

will shift towards the side with fewer moles of gas to decrease the pressure.

Therefore, the equilibrium position will shift to the right (towards the products).

Step 5: As a result, the equilibrium concentration of SO3will increase, while

the concentrations of SO2and O2will decrease.

Step 6: This shift towards the products ensures that the system partially

relieves the increase in pressure by reducing the total number of gas molecules

in the system, thereby restoring equilibrium.

Question 28

Question

Consider the following equilibrium in a sealed container at constant tempera-

ture:

N2(g) + 3H2(g)⇌2NH3(g)

If the pressure in the container is increased, predict the direction in which

the equilibrium will shift and explain why.

Solution

Step 1: Determine the effect of increasing pressure on the equilibrium.

Increasing the pressure of a system at equilibrium favors the side of the

reaction with fewer gas molecules. In this case, the reaction contains 4 moles of

gas on the left side (N2 and 3H2) and 2 moles of gas on the right side (2NH3).

Therefore, increasing the pressure will shift the equilibrium to the side with

fewer gas molecules, which is the right side.

Step 2: Justify the shift using Le Chatelier’s Principle.

Le Chatelier’s Principle states that when a system at equilibrium is subjected

to a stress, the system will shift in a direction that helps relieve that stress. In

this case, increasing the pressure is the stress on the system. To relieve this

stress, the equilibrium will shift to the side with fewer gas molecules, which is

the right side of the reaction. This will help reduce the pressure in the container.

Question 29

Question

Consider the following reaction:

2 H2O(g)⇌2 H2(g)+O2(g)

If the pressure on the system is decreased, predict the effect on the equi-

librium position in terms of the concentrations of the reactants and products.

Justify your answer.

Solution

To determine the effect of a change in pressure on the equilibrium position of

a reaction, we need to consider Le Chatelier’s Principle. When the pressure

is decreased, the system will shift in a direction that reduces the change in

pressure.

Step 1: Identify the initial response to a decrease in pressure When

the pressure is decreased, the system will shift to the side with more moles of

gas to counteract the change and increase the pressure.

Step 2: Analyze the given reaction The given reaction is:

2 H2O(g)⇌2 H2(g)+O2(g)

On the left side of the reaction, there are 2 moles of gas (from water vapor),

and on the right side, there are 3 moles of gas (from hydrogen and oxygen gas).

Step 3: Predict the effect on the equilibrium position Since there

are more moles of gas on the right side of the reaction, the equilibrium will

shift to the right to counteract the decrease in pressure. This means that the

concentrations of H2and O2will increase, and the concentration of H2O will

decrease.

Therefore, when the pressure is decreased, the equilibrium position will shift

to the right, favoring the formation of H2and O2gases.

Question 30

Question

Consider the following equilibrium reaction:

2SO2(g)+O2(g)⇌2SO3(g)

Describe how each of the following changes will affect the position of equi-

librium. Justify your answers:

1. Increase in the pressure of the system

2. Addition of more SO2gas

3. Increase in the temperature of the system

Solution

To analyze the effects of changes on the position of equilibrium, we can apply

Le Chatelier’s Principle, which states that a system at equilibrium will respond

to a stress by shifting the equilibrium position in the direction that counteracts

the imposed stress.

1. Increase in the pressure of the system:

Step 1: According to Le Chatelier’s Principle, if the pressure of the

system is increased, the system will shift in the direction that reduces the

total number of gas molecules.

Step 2: In this equilibrium reaction, there are three moles of gas on the

left side (2 moles of SO2 and 1 mole of O2) and two moles of gas on the

right side (2 moles of SO3).

Step 3: Increasing the pressure will cause the system to shift to the side

with fewer gas molecules to reduce the pressure. Therefore, the equilib-

rium will shift to the right, favoring the formation of more SO3.

2. Addition of more SO2gas:

Step 1: If more SO2gas is added, the system will shift to counteract this

change.

Step 2: The equilibrium will shift to the right to consume the excess SO2that

was added.

3. Increase in the temperature of the system:

Step 1: Increasing the temperature will favor the endothermic reaction in this

case.

Step 2: The endothermic reaction is the forward reaction, which means the

equilibrium will shift to the right to absorb the added heat.

Question 31

Question

Consider the reaction:

2H2O(g) ⇌2H2(g) + O2(g)

If the volume of the reaction vessel is decreased, suggest what will happen to the

equilibrium position, and explain your answer using Le Chatelier’s Principle.

Solution

Step 1: When the volume of the reaction vessel is decreased, the concentration

of the gases in the vessel will increase due to the decrease in volume. This will

result in an increase in pressure inside the vessel. According to Le Chatelier’s

Principle, the system will respond in a way that opposes the change applied to

it.

Step 2: In this case, increasing the pressure will favor the side of the reaction

with fewer gas molecules in order to decrease the pressure. Since there are 3

moles of gas on the right side of the reaction and only 2 moles of gas on the left

side, the equilibrium will shift to the left.

Step 3: Thus, when the volume of the reaction vessel is decreased, the

equilibrium position of the reaction will shift to the left, favoring the formation of

more water vapor (liquid water will increase), and decreasing the concentrations

of hydrogen gas and oxygen gas.

Question 32

Question

Consider the following reaction at equilibrium:

2SO2(g)+O2(g)⇌2SO3(g)

If the pressure inside the container is increased by adding an inert gas at

constant volume, predict the direction in which the equilibrium will shift. Justify

your answer using Le Chatelier’s Principle.

Solution

Step 1: According to Le Chatelier’s Principle, when a stress is applied to a

system at equilibrium, the system will adjust in order to minimize the effect of

the stress and restore equilibrium.

Step 2: By adding an inert gas at constant volume, the total pressure inside

the container increases.

Step 3: In this reaction, the number of moles of gas in the reactants side is

3 (2 moles of SO2 and 1 mole of O2) whereas the number of moles of gas in the

products side is 2 (2 moles of SO3).

Step 4: Increasing the total pressure in the container will favor the side of

the reaction with fewer moles of gas in order to alleviate the stress.

Step 5: Therefore, the equilibrium will shift to the left, favoring the reactants

side (2SO2 + O2) in order to reduce the total pressure back to its original value.

Question 33

Question

Consider the following equilibrium reaction:

2 H2(g) + O2(g) ⇌2 H2O(g)

If the temperature of the system is increased, predict the direction in which

the equilibrium will shift according to Le Chatelier’s Principle. Justify your

answer.

Solution

Step 1: When the temperature of a reaction at equilibrium is increased, the

system will respond in a way that reduces the temperature increase. For an

exothermic reaction like this one, the reaction releases heat when it proceeds in

the forward direction (from reactants to products).

Step 2: By increasing the temperature, the system will shift to the left (to-

wards the reactants) to absorb the excess heat. This is because in an exothermic

reaction, the reverse reaction is endothermic, and absorbing heat will help to

counteract the temperature increase.

Step 3: Therefore, in this reaction, increasing the temperature will cause the

equilibrium to shift towards the left, favoring the formation of more reactants

– hydrogen and oxygen gas.

Question 34

Question

An equilibrium reaction is given by the equation:

PCl5⇌PCl3+ Cl2

If the pressure is increased by adding an inert gas at constant volume, predict

the effect on the concentrations of PCl5, PCl3, and Cl2in the reaction vessel,

according to Le Chatelier’s Principle.

Solution

Step 1: Identify the effect of increasing pressure. - Adding an inert gas at

constant volume will increase the total pressure in the reaction vessel.

Step 2: Apply Le Chatelier’s Principle. - Increasing the pressure of a system

at equilibrium tends to shift the equilibrium in the direction that decreases the

total number of gaseous molecules.

Step 3: Analyze the number of gaseous molecules in the reaction. - On the

reactant side, there is only 1 gaseous molecule (PCl5). - On the product side,

there are 2 gaseous molecules (PCl3and Cl2).

Step 4: Predict the effect on the equilibrium. - Increasing the pressure will

shift the equilibrium to the side with fewer gaseous molecules to decrease the

total number of molecules.

Step 5: Predict the changes in concentrations. - The equilibrium will shift

to the left, favoring the formation of PCl5. - As a result, the concentration of

PCl5will increase, while the concentrations of PCl3and Cl2will decrease.

Question 2

Question

Consider the reaction:

2A(g) + B(g)⇌3C(g)

Suppose the reaction is at equilibrium at a certain temperature. If the pres-

sure of the system is increased by decreasing the volume of the container, pre-

dict the direction in which the equilibrium will shift according to Le Chatelier’s

Principle. Justify your answer.

Solution

Step 1: When the pressure of a system at equilibrium is increased by decreasing

the volume of the container, the system will shift to reduce the pressure. Step 2:

Since the total number of moles of gas on the left side of the reaction (2A(g) +

B(g)) is greater than on the right side (3C(g)), decreasing the volume will cause

the system to shift in the direction that consumes gas molecules. Step 3: As a

result, the equilibrium will shift to the right to decrease the total pressure by

favoring the formation of product, 3C(g).

Question 3

Question

Consider the following equilibrium reaction:

2 NOBr(g) ⇌2 NO(g) + Br2(g)

If the concentration of NOBr is increased, predict the direction in which the

equilibrium will shift according to Le Chatelier’s Principle. Justify your answer.

Solution

Step 1: Le Chatelier’s Principle states that if a system at equilibrium is sub-

jected to a stress (such as a change in concentration, pressure, or temperature),

the system will adjust in order to counteract the stress.

Step 2: In this case, if the concentration of NOBr is increased, the system

will shift in the direction that consumes NOBr in order to decrease the ex-

cess concentration. This means the system will shift to the right, favoring the

formation of products (NO and Br2).

Step 3: The equilibrium reaction can be represented as:

2 NOBr(g) ⇌2 NO(g) + Br2(g)

Step 4: When the concentration of NOBr is increased, the system will shift

to the right to consume the excess NOBr. This will result in an increase in the

concentrations of NO and Br2, favoring the formation of products.

Step 5: Therefore, the equilibrium will shift to the right when the concen-

tration of NOBr is increased, according to Le Chatelier’s Principle.

Question 4

Question

Consider the following equilibrium reaction:

H2O(g) ⇌H2O(l)

If the temperature of the system is increased, predict how Le Chatelier’s

Principle will affect the equilibrium position and justify your answer.

Solution

Step 1: When the temperature of the system is increased, the equilibrium will

shift in the direction that absorbs heat.

Step 2: In this case, the forward reaction (from gas to liquid) is endothermic

since it absorbs heat to break intermolecular forces and increase disorder. Thus,

an increase in temperature will favor the endothermic forward reaction to absorb

the additional heat.

Step 3: As a result, the equilibrium position will shift to the right, favoring

the formation of more liquid water molecules.

Step 4: Therefore, according to Le Chatelier’s Principle, increasing the tem-

perature will cause the equilibrium position to shift towards the formation of

more liquid water molecules.

Question 5

Question

Consider the following equilibrium reaction:

2 SO2(g)+O2(g)⇌2 SO3(g)

At a certain temperature, the equilibrium constant, K, for the reaction above

is 50. If a student adds a catalyst to the reaction vessel, which of the following

changes will occur to the system (increase, decrease, or remain unchanged): the

concentration of SO3, the concentration of SO2, the concentration of O2, and

the value of the equilibrium constant, K? Justify your answer.