CHEM 131 - ADVANCED GENERAL CHEMISTRY I Le Chatelier's Principle Question Bank Set 1

CHEM 131 - ADVANCED GENERAL

CHEMISTRY I - Le Chatelier’s

Principle

Question Bank - Set 1

Liberty University

Question 1

Question

Consider the following equilibrium reaction:

N2(g) + 3H2(g)⇌2NH3(g)

If the concentration of H2gas is increased, predict qualitatively how the

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

your answer.

Solution

To predict how the equilibrium position will shift when the concentration of H2

gas is increased, we can apply Le Chatelier’s Principle.

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

the reactants (or products) in an equilibrium reaction is increased, the equilib-

rium position will shift in the direction that reduces the concentration of that

species.

Step 2: In this reaction, increasing the concentration of H2gas (a reactant)

will cause the system to shift toward the products side to relieve the stress of

the increased concentration of H2.

Step 3: Therefore, the equilibrium position will shift to the right, favoring

the formation of more NH3gas, in order to decrease the concentration of the

added H2.

Hence, the equilibrium position will shift to the right to produce more NH3

gas when the concentration of H2gas is increased, according to Le Chatelier’s

Principle.

Question 2

Question

Consider the reaction:

2 NO(g)+ Br2(g)⇌2 NOBr(g)

If the equilibrium constant, Kc, for the reaction at 500 K is 0.075, predict the

direction in which the reaction will shift if the pressure is increased at constant

temperature.

Solution

Le Chatelier’s Principle states that if a system at equilibrium is perturbed by a

change in conditions, the equilibrium will shift to counteract the change.

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

- Since there are 3 moles of gas on the left side of the reaction and only 2

moles of gas on the right side, increasing the pressure will cause the reaction to

shift to the side with fewer moles of gas to reduce the pressure.

Step 2: Determine the initial reaction quotient, Qc.

- The initial reaction quotient, Qc, is calculated using the same expression as

the equilibrium constant, but with initial concentrations instead of equilibrium

concentrations.

Qc=[NOBr]2

[NO]2·[Br2]

Step 3: Compare Qcto Kc.

- If Qc< Kc, the reaction will shift to the right to produce more products.

- If Qc> Kc, the reaction will shift to the left to produce more reactants.

Step 4: Predict the direction of the reaction shift.

- Since the initial reaction mixture contains no products (NOBr), Qc= 0. -

Since Qc< Kc, the reaction will shift to the right to produce more NOBr and

reach equilibrium.

Therefore, if the pressure is increased at 500 K, the reaction will shift to the

right to produce more NOBr in order to decrease the pressure back to its initial

value.

Question 3

Question

Consider the following reaction at equilibrium:

2SO2(g)+O2(g)⇌2SO3(g)

If the concentration of SO2is increased, predict the direction in which the

equilibrium will shift and explain why using Le Chatelier’s Principle.

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, temperature, or pressure),

the system will react in a way that opposes the stress.

Step 2: In this case, by increasing the concentration of SO2, the system will

sense an excess of SO2molecules and will try to use up some of them to establish

a new equilibrium.

Step 3: Therefore, the equilibrium will shift to the right, towards the forma-

tion of more SO3molecules, in order to decrease the concentration of SO2back

to the original equilibrium level.

Step 4: As a result of the shift to the right, the concentration of SO3will

increase, while the concentrations of SO2and O2will decrease.

Step 5: This shift ultimately helps to counteract the increase in SO2con-

centration and restore the equilibrium position of the reaction.

Question 4

Question

Consider the following equilibrium:

2 SO2(g) + O2(g) ⇌2 SO3(g)

If the equilibrium mixture is disturbed by increasing the pressure, predict

the direction in which the equilibrium will shift and justify your answer.

Solution

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

Increasing the pressure will shift the equilibrium towards the side with fewer

gas molecules to reduce the pressure.

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

equilibrium.

Initially, there are 3 gas molecules on the left side ((2 ×SO2)+O2) and 2

gas molecules on the right side (2 ×SO3).

Step 3: Compare the total number of gas molecules on each side.

Since there are fewer gas molecules on the right side of the equilibrium, an

increase in pressure will cause the equilibrium to shift towards the right side to

reduce the pressure.

Step 4: Write the equilibrium expression for the reaction.

The equilibrium expression for the reaction is given by:

K=[SO3]2

[SO2]2[O2]

Step 5: Justify the direction in which the equilibrium will shift.

The equilibrium will shift to the right to decrease the total number of gas

molecules and reduce the pressure, favoring the formation of more SO3.

Therefore, the equilibrium will shift to the right if the pressure is increased.

Question 5

Question

Consider the reaction:

2NOCl(g)⇌2NO(g) + Cl2(g)

If the volume of the reaction vessel is suddenly decreased, predict the direc-

tion of shift for this equilibrium reaction according to Le Chatelier’s Principle.

Provide a detailed explanation for your choice.

Solution

To analyze the effect of a sudden decrease in volume on this equilibrium reaction,

we should consider the changes in pressure and concentrations of the reactants

and products.

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

inside the vessel increases since the number of gas molecules in the system

remains constant.

Step 2: According to Le Chatelier’s Principle: - An increase in pressure

will cause the system to shift in a direction that reduces the total number of gas

molecules. - A decrease in pressure will cause the system to shift in a direction

that increases the total number of gas molecules.

Step 3: In this given reaction, there are 3 moles of gas on the left side (2

moles of NOCl and 1 mole of Cl2) and 4 moles of gas on the right side (2 moles

of NO).

Step 4: Since the volume is decreased, pressure is increased. To reduce

the pressure, the system will shift in the direction of more moles of gas, which

means the equilibrium position will shift towards the right side of the reaction

to increase the concentration of gas molecules.

Step 5: Therefore, in response to the sudden decrease in volume, the equi-

librium will shift to the right, favoring the formation of more NO and Cl2from

NOCl.

Question 6

Question

Consider the following equilibrium reaction:

2SO2(g)+ O2(g)⇌2SO3(g)

If the concentration of SO2(g)is increased while maintaining the volume and

temperature constant, 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

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

will adjust to counteract the change and restore equilibrium.

Step 2: In this case, if the concentration of SO2(g)is increased, the system

will react in such a way as to counteract the change. Since SO2(g)is a reactant in

the forward reaction, increasing its concentration will drive the reaction towards

the products side to consume the excess reactant.

Step 3: Therefore, the equilibrium will shift to the right, producing more

SO3(g)until a new equilibrium is established.

Step 4: In conclusion, an increase in the concentration of SO2(g)will cause

the equilibrium to shift towards the products side to partially alleviate the

increase in SO2(g)concentration.

Question 7

Question

Consider the following equilibrium reaction:

N2O4(g)⇌2NO2(g)

If the concentration of N2O4is increased at constant temperature, describe how

the system will respond based on Le Chatelier’s Principle.

Solution

To determine how the system will respond when the concentration of N2O4is

increased at constant temperature, we can analyze Le Chatelier’s Principle.

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

reactant is increased, the system will shift to consume the added reactant. In

this case, increasing the concentration of N2O4will cause the reaction to shift

to the right to consume more N2O4.

Step 2: By shifting to the right, more N2O4will be consumed, producing

more NO2until a new equilibrium is established.

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

to an increase in the concentration of NO2and a decrease in the concentration

of N2O4to partially offset the increase in N2O4concentration.

Therefore, when the concentration of N2O4is increased at constant tem-

perature, the system will shift to the right to consume more N2O4until a new

equilibrium is reached.

Question 8

Question

Consider the following reaction at equilibrium:

2 SO2(g)+O2(g)⇌2 SO3(g)

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

the left, right, or remain unchanged? Justify your answer using Le Chatelier’s

Principle.

Solution

To determine the effect of an increase in temperature on the equilibrium position

of the given reaction, we need to consider Le Chatelier’s Principle. This principle

states that if a system at equilibrium is subjected to a stress, the system will

adjust itself in order to counteract the effect of that stress.

Step 1: Reaction Quotient First, let’s write the equilibrium constant ex-

pression for the reaction:

Keq =[SO3]2

[SO2]2×[O2]

Step 2: Effect of Increase in Temperature An increase in temperature is a

stress on the system. In this case, the reaction is exothermic (negative change in

enthalpy), meaning the forward reaction is favored by a decrease in temperature.

Therefore, an increase in temperature will be considered a stress that the system

will try to counteract.

Step 3: Shift in Equilibrium To counteract the increase in temperature,

the equilibrium will shift in the endothermic direction to absorb the extra heat.

This means the equilibrium will shift to the left (towards the reactants) in order

to consume heat.

Therefore, the equilibrium will shift to the left when the temperature of the

system is increased.

Question 9

Question

Consider the following reaction at equilibrium:

2SO2(g)+O2(g)⇌2SO3(g)

If the temperature is increased, predict the direction in which the equilibrium

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

Solution

Step-by-step solution:

Step 1: When the temperature is increased, the system will attempt to coun-

teract this change. In this case, since the reaction is exothermic (produces heat),

adding heat to the system will cause the equilibrium to shift in the direction

that consumes the excess heat.

Step 2: In the given reaction, the forward reaction is exothermic (heat is a

product). Therefore, increasing the temperature will cause the reaction to shift

in the reverse direction to consume the excess heat.

Step 3: As a result, when the temperature is increased, the equilibrium will

shift to the left, favoring the formation of more reactants (2SO2and O2)andreducingtheformationofproducts(2SO3).

Question 10

Question

Consider the following equilibrium reaction:

2 SO2(g)+O2(g)⇌2 SO3(g) + 118 kJ/mol

If the concentration of O2(g) is increased, predict the direction in which the

equilibrium will shift according to Le Chatelier’s Principle.

Solution

Step 1: When the concentration of O2(g) is increased, the system will try to

counteract this change by shifting the equilibrium to the side that consumes

O2(g). In this case, the forward reaction consumes O2(g), so the equilibrium

will shift to the right.

Step 2: By shifting to the right, more SO3(g) will be formed.

Therefore, according to Le Chatelier’s Principle, if the concentration of O2(g)

is increased, the equilibrium will shift to the right to produce more SO3(g).

Question 11

Question

Consider the following equilibrium reaction:

N2O4(g)⇌2NO2(g)

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

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

Principle. Justify your answer.

Solution

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

increased by decreasing the volume, we need to analyze the changes caused by

the pressure increase and apply Le Chatelier’s Principle.

Step 1: Identify the effect of the pressure change on the equi-

librium system. When the volume of the system is decreased, the pressure

will increase. According to Le Chatelier’s Principle, the system will respond by

shifting the equilibrium to counteract this change.

Step 2: Determine the reaction that will alleviate the increase in

pressure. In this case, decreasing the volume increases the pressure, so the

system will want to reduce the total number of particles in order to decrease

the pressure.

Step 3: Analyze the stoichiometry of the reaction. In the given

reaction, one mole of N2O4 gas dissociates to form two moles of NO2 gas.

Therefore, the total number of moles of gas will decrease when N2O4 dissociates

to form NO2.

Step 4: Apply Le Chatelier’s Principle. To decrease the pressure

caused by the volume decrease, the equilibrium will shift in the direction that

reduces the total number of gas molecules. In this case, the equilibrium will

shift to the left to decrease the pressure. This means that more N2O4 will be

formed at equilibrium.

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

equilibrium will shift towards the left to favor the formation of more N2O4 gas

molecules and alleviate the pressure increase.

Question 12

Question

Consider the equilibrium reaction:

2AB(g)⇌A2(g) + B2(g)

If the volume of the container is decreased, predict the direction in which the

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

with an explanation.

Solution

Step 1: When the volume of the container is decreased, the system will try to

counteract the change by shifting the equilibrium in a direction that will relieve

the stress caused by the volume change.

Step 2: The volume decrease causes the pressure to increase. According to

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

total number of gas molecules so that the pressure can decrease.

Step 3: Look at the stoichiometry of the reaction. On the left side, there

are 2 moles of gas (2AB), and on the right side, there are 2 moles of gas (A2 +

B2). Since the number of gas molecules is the same on both sides, changing the

volume won’t change the pressure.

Step 4: Therefore, the equilibrium will not shift in either direction when the

volume is decreased in this particular reaction.

Question 13

Question

For the reaction below at equilibrium:

2 NO(g)+O2(g)⇌2 NO2(g)

Predict the effect of the following changes on the equilibrium position (shift to

the right, shift to the left, or no change):

1. Increasing the concentration of NO.

2. Decreasing the volume of the container.

3. Adding an inert gas at constant volume.

Solution

1. Increasing the concentration of NO will shift the equilibrium position to

the right. According to Le Chatelier’s Principle, adding more reactant

will cause the system to shift in the direction that consumes the added

species. By increasing the concentration of NO, the system will favor the

forward reaction to consume the excess NO. Therefore, the equilibrium

position shifts to the right.

2. Decreasing the volume of the container will shift the equilibrium position

to the side with fewer moles of gas molecules. In this reaction, there are

3 moles of gas molecules on the left side (2 NO + 1 O2) and 2 moles

of gas molecules on the right side (2 NO2). Decreasing the volume will

increase the pressure, favoring the side with fewer moles of gas molecules.

Therefore, the equilibrium position will shift to the right.

3. Adding an inert gas at constant volume will have no effect on the equilib-

rium position. Inert gases do not participate in the reaction, so adding an

inert gas will simply increase the total pressure without affecting the par-

tial pressures of the reactants and products. Therefore, the equilibrium

position will remain unchanged.

Question 14

Question

Consider the equilibrium reaction:

H2O(g)⇌H2O(l)

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

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

Solution

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

of the system is increased, we can apply Le Chatelier’s Principle, which states

that when a system at equilibrium is subjected to a stress, it will adjust to

counteract the stress and re-establish equilibrium.

Step 1: Increase in pressure will shift the equilibrium in the direction that

reduces the total number of moles of gas in the system.

Given the equilibrium reaction:

H2O(g)⇌H2O(l)

In this reaction, there is 1 mole of gas on the left side (g) and 0 moles of gas

on the right side (l). Increasing the pressure will shift the equilibrium to the

side with fewer moles of gas to alleviate the stress.

Step 2: Therefore, when the pressure is increased, the equilibrium will shift

to the right (towards the liquid phase) to reduce the total number of moles of

gas in the system.

Thus, the equilibrium will shift towards the formation of liquid water (H2O(l))

when the pressure of the system is increased.

Question 15

Question

Consider the following reaction at equilibrium:

H2O(g)⇌H2O(l)

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

(shifts left, shifts right, or no effect)? Justify your answer.

1. Increasing the pressure by decreasing the volume of the container.

2. Adding more water vapor to the system.

3. Increasing the temperature.

Solution

1. Increasing the pressure by decreasing the volume of the container:



According to Le Chatelier’s Principle, when the pressure of a system at

equilibrium is increased, the reaction will shift in the direction that reduces

the total number of moles of gas.



In this case, by decreasing the volume of the container and increasing the

pressure, the reaction will shift towards the side with fewer gas molecules

to decrease the pressure. Since there are no gas molecules in the liquid

phase, the reaction will shift to the left (towards the gaseous phase) to

decrease the pressure.



Therefore, the equilibrium will shift to the left when the pressure is in-

creased.

2. Adding more water vapor to the system:



Adding more water vapor to the system increases the concentration of

water vapor in the reaction mixture.



According to Le Chatelier’s Principle, an increase in the concentration of

a reactant will shift the equilibrium position to the right to reduce the

excess reactant.



Therefore, adding more water vapor will cause the equilibrium to shift to

the right.

3. Increasing the temperature:



When the temperature of a system at equilibrium is increased, the reaction

will shift in the endothermic direction to absorb the added heat.



Since the forward reaction in this case is endothermic (consuming heat),

increasing the temperature will favor the endothermic reaction (vaporiza-

tion of water). As a result, the equilibrium will shift to the right (towards

the vapor phase) to consume the added heat.



Therefore, increasing the temperature will cause the equilibrium to shift

to the right.

Question 16

Question

Consider the following reaction at equilibrium:

PCl5(g)⇌PCl3(g) + Cl2(g)

If the volume of the container is decreased, predict the direction in which

the equilibrium will shift and explain why.

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 volume),

the equilibrium will shift in a direction that counteracts the change in order to

restore equilibrium.

Step 2: If the volume of the container is decreased, the total pressure of the

system will increase.

Step 3: According to the reaction equation, 1 mole of PCl produces 1 mole

of PCl and 1 mole of Cl. Therefore, the number of moles of gas on the left side

is greater than the number of moles of gas on the right side.

Step 4: Increasing the pressure will favor the side of the reaction with fewer

moles of gas, in this case, the products side.

Step 5: Therefore, when the volume is decreased (increasing the pressure),

the equilibrium will shift to the right, favoring the formation of PCl and Cl.

Question 17

Question

Consider the equilibrium reaction:

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. Provide a brief

explanation for your answer.

Solution

1. According to Le Chatelier’s Principle, when a system at equilibrium is sub-

jected to a stress (such as a change in temperature), the system will shift in the

direction that reduces the effect of that stress.

2. In this case, an increase in temperature is considered as a stress on the

system.

3. Since the reaction involving the formation of sulfur trioxide (SO3) is

exothermic (i.e., releases heat), the forward reaction is favored at lower temper-

atures to counteract the increase in temperature.

4. Therefore, if the temperature of the system is increased, the equilibrium

will shift to the left (to the reactants) to consume the excess heat by favoring

the endothermic reaction.

5. Overall, the equilibrium will shift to the left to form more 2SO2(g) and

O2(g) to counteract the increase in temperature.

Question 18

Question

Consider the reaction involving nitrogen dioxide gas:

2NO2(g)⇌N2O4(g)

If the pressure is increased by adding more NO gas to the system at equi-

librium, predict the direction in which the reaction will shift according to Le

Chatelier’s Principle. Justify your answer with an explanation.

Solution

To determine the direction in which the reaction will shift upon the increase

in pressure, we need to consider Le Chatelier’s Principle. When a system at

equilibrium is subjected to a change in conditions, the system will respond in a

way that minimizes the effect of the change.

Step 1: Increase in Pressure - When more NO gas is added to the system,

the total pressure of the system increases. - This change in pressure stresses the

equilibrium established by the reaction.

Step 2: Prediction - According to Le Chatelier’s Principle, the system will

shift in a direction that reduces the total pressure. - Since the forward reaction

produces more moles of gas than the reverse reaction, the system will shift to

the side with fewer moles of gas to decrease the pressure.

Step 3: Justification - In the given equilibrium reaction, 2 moles of NO gas

produce 1 mole of NO gas. - By increasing the pressure, the system will shift

to the left, favoring the reverse reaction that consumes NO gas and produces

NO gas to reduce the total pressure. - Therefore, the system will shift left to

decrease the total pressure by consuming some of the added NO gas.

Therefore, upon increasing the pressure by adding more NO gas, the reac-

tion will shift to the left to decrease the total pressure in accordance with Le

Chatelier’s Principle.

Question 19

Question

Consider the equilibrium reaction:

2 SO2(g)+O2(g)⇌2 SO3(g)

If the concentration of O2is increased at constant temperature and pressure,

what will be the effect on the equilibrium position? Justify your answer.

Solution

Step 1: Write the equilibrium expression for the reaction. The equilibrium

expression can be written as:

K=[SO3]2

[SO2]2[O2]

Step 2: Determine the reaction quotient (Q) to understand the current

position of the reaction. Let’s denote the initial concentrations as follows:

[SO2]0=amol/L, [O2]0=bmol/L, [SO3]0=cmol/L, where a,b, and c

are initial concentrations in mol/L.

The initial value of the reaction quotient Qis:

Q=c2

a2b

Step 3: Analyze the effect of increasing the concentration of O2. If the

concentration of O2is increased, the denominator of the equilibrium expression

will increase. As a result, the value of Qwill become smaller than K.

Step 4: Determine the direction of the reaction shift. Since Qis now smaller

than K, the reaction will shift to the right to re-establish equilibrium. This

means that more SO3will be produced.

Step 5: Conclusion Increasing the concentration of O2at constant temper-

ature and pressure will cause the equilibrium position to shift to the right,

favoring the formation of more SO3.

Question 20

Question

Consider the following reaction at equilibrium:

N2(g)+ 3H2(g)⇌2NH3(g)

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

reaction? Use Le Chatelier’s Principle to explain your answer.

1. Increasing the pressure by decreasing the volume of the container.

2. Adding more N2 gas to the reaction mixture.

3. Removing some of the NH3 gas from the reaction mixture.

Solution

To determine the effect of each change on the equilibrium position of the reac-

tion, we will analyze the reaction using Le Chatelier’s Principle.

1. Increasing the pressure by decreasing the volume of the con-

tainer:



Prediction: According to Le Chatelier’s Principle, when the pressure is

increased, the system will shift towards the side with fewer gas molecules

to decrease the pressure.



The total number of gas molecules on the left side of the reaction is 4 (1

N2 + 3 H2), and on the right side of the reaction is 2 NH3. Therefore,

shifting towards the reactants side will minimize the pressure.



Conclusion: Decreasing the volume of the container will cause the equi-

librium to shift to the left side of the reaction.

2. Adding more N2 gas to the reaction mixture:



Prediction: Increasing the concentration of N2 will disturb the equilib-

rium position. To counteract the increase in N2 concentration, the system

will shift towards the products side to consume some of the N2.



The reaction moves to the right to balance the change: N2(g)+ 3H2(g)⇌

2NH3(g).



Conclusion: Adding more N2 gas will cause the equilibrium to shift to

the products side of the reaction.

3. Removing some of the NH3 gas from the reaction mixture:



Prediction: Removing NH3 from the system will disrupt the equilibrium.

To counteract the decrease in NH3 concentration, the system will shift

towards the reactants side to produce more NH3.



The reaction moves to the right to balance the change: N2(g)+ 3H2(g)⇌

2NH3(g).



Conclusion: Removing some NH3 gas will cause the equilibrium to shift

to the left side of the reaction.

Question 21

Question

Consider the reaction:

2 CO(g)+O2(g)⇌2 CO2(g)

If the concentration of CO(g) is increased at constant temperature and pressure,

explain how the system will shift to re-establish equilibrium according to Le

Chatelier’s Principle.

Solution

Step 1: First, determine the effect of increasing the concentration of CO(g) on

the reaction. Since CO(g) is a reactant in the forward reaction, adding more

CO(g) will shift the equilibrium to the right to consume the additional CO(g).

Step 2: According to Le Chatelier’s Principle, in response to the increase in

concentration of CO(g), the system will shift to the right to consume the added

CO(g). This is to counteract the change and re-establish equilibrium.

Step 3: As the system shifts to the right, more CO2(g) will be formed while

the amounts of CO(g) and O2(g) will decrease to re-establish equilibrium.

Step 4: Therefore, increasing the concentration of CO(g) will lead to an

increase in the concentration of CO2(g) and a decrease in the concentrations of

CO(g) and O2(g) until a new equilibrium is reached.

Question 22

Question

Consider the reaction 2SO2(g) + O2(g)⇌2SO3(g). If the concentration of

SO2is increased, predict the effect on the equilibrium position and justify your

answer.

Solution

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

a change, the system will adjust in order to counteract that change and partially

offset it. In this case, we are increasing the concentration of SO2in the reaction

2SO2(g) + O2(g)⇌2SO3(g). Let’s analyze the effect of this change on the

equilibrium position.

Step 1: Determine the effect of increasing the concentration of SO2on the

reaction.

Increasing the concentration of SO2will shift the equilibrium to the right

in order to decrease the concentration of SO2and partially offset the change.

This can be illustrated by the following reaction quotient expression:

Q=[SO3]2

[SO2]2[O2]

Step 2: Rationalize the shift in equilibrium.

Increasing the concentration of SO2will lead to an increase in the numerator

of the reaction quotient. As a result, the reaction quotient Qwill be greater

than the equilibrium constant K. The system will shift to the right to consume

some of the excess SO2and produce more SO3until Qdecreases back to equal

Therefore, increasing the concentration of SO2will cause the equilibrium

position to shift to the right, favoring the formation of SO3in order to partially

offset the increase in SO2concentration.

Question 23

Question

Consider the following equilibrium reaction:

2NO2(g)⇌N2O4(g)

If the temperature is increased, predict the direction in which the equilibrium

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

explanation.

Solution

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

subjected to a change, the system will react in a way that partially counteracts

the effect of the change in order to restore equilibrium.

Step 2: In this reaction, the forward reaction (to the right) is endothermic,

meaning it absorbs heat. By increasing the temperature, the system will react

to counteract this increase in heat.

Step 3: Increasing the temperature will cause the equilibrium to shift in

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

left, favoring the reactants.

Step 4: Therefore, in the given equilibrium reaction, an increase in tem-

perature will cause the equilibrium to shift to the left, favoring the formation

of more NO2(g).

Question 24

Question

Consider the reaction:

N2(g) + 3H2(g) ⇌2NH3(g)

If the pressure of the system is increased while maintaining a constant tem-

perature, predict the direction in which the equilibrium will shift according to

Le Chatelier’s Principle. Justify your answer using the reaction stoichiometry

and principles of equilibrium.

Solution

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

- Increasing pressure will favor the side of the reaction with fewer molecules

of gas in order to decrease the total gas volume.

Step 2: Determine the stoichiometry of the reaction.

- On the reactant side, there is a total of 1 + 3 = 4 molecules of gas. - On

the product side, there are 2 molecules of gas.

Step 3: Apply Le Chatelier’s Principle to predict the direction of the equi-

librium shift.

- Since there are fewer molecules of gas on the product side, the equilibrium

will shift towards the side with fewer molecules of gas to reduce the total volume

and relieve the increase in pressure. - Therefore, the equilibrium will shift to

the left, favoring the formation of reactants N2and H2.

Therefore, increasing the pressure of the system will cause the equilibrium

to shift to the left to maintain equilibrium.

Question 25

Question

Consider the reaction:

2 SO2(g)+O2(g)⇌2 SO3(g)

If the volume of the container is decreased, explain how the equilibrium will

shift according to Le Chatelier’s Principle.

Solution

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

container will increase according to the ideal gas law.

Step 2: In this reaction, the total number of moles of gas on the left side (2

moles of SO2) is greater than the total number of moles of gas on the right side

(2 moles of SO3).

Step 3: According to Le Chatelier’s Principle, when the volume is decreased

(resulting in an increase in pressure), the equilibrium will shift in the direction

that produces a decrease in the total number of moles of gas.

Step 4: In this case, the equilibrium will shift to the right (towards the

side with fewer moles of gas) to relieve the increase in pressure caused by the

decrease in volume.

Step 5: Therefore, the equilibrium will shift to produce more SO3gas

molecules, resulting in an increase in the concentration of SO3.

Question 26

Question

Consider the reaction:

N2(g) + 3H2(g)⇌2NH3(g)

If the concentration of nitrogen gas is increased while keeping the volume

constant, predict the direction in which the equilibrium will shift according to

Le Chatelier’s Principle. Justify your answer with an explanation.

Solution

Step 1: Identify the Initial Equilibrium The initial equilibrium can be repre-

sented as:

N2(g) + 3H2(g)⇌2NH3(g)

Step 2: Predict the Shift in Equilibrium When the concentration of the

reactant (nitrogen gas) is increased by keeping the volume constant, the system

will respond by adjusting the equilibrium position. According to Le Chatelier’s

Principle, the equilibrium will shift to counteract the increase in nitrogen gas

concentration.

Step 3: Justify the Prediction Increasing the concentration of nitrogen gas

causes the system to shift to the right in order to reduce the excess nitrogen

gas. This is achieved by consuming some of the nitrogen gas to produce more

ammonia until a new equilibrium is established. Therefore, the equilibrium will

shift to the right to form more ammonia.

Thus, the equilibrium will shift to the right to produce more ammonia gas

in response to the increase in nitrogen gas concentration.

Question 27

Question

For the reaction

2CO(g)+O2(g)⇌2CO2(g),

which is exothermic, explain how each of the following changes affects the Equi-

librium state of the system. Will the equilibrium shift left, right, or remain

unchanged if:

(a) The pressure is increased by decreasing the volume of the container.

(b) Some CO is added to the system.

Solution

(a) The pressure is increased by decreasing the volume of the container:



Step 1: Think about the effect of increasing the pressure on the equilib-

rium system. According to Le Chatelier’s principle, when the pressure is

increased, the equilibrium will shift in the direction that produces fewer

moles of gas to relieve the pressure.



Step 2: In this reaction, there are 3 moles of gas on the left side (2CO)

and 2 moles of gas on the right side (2CO2).



Step 3: Increasing the pressure will shift the equilibrium to the side with

fewer moles of gas to reduce the pressure, so the equilibrium will shift to

the right.

(b) Some CO is added to the system:



Step 1: Consider the effect of adding more CO to the system. According

to Le Chatelier’s principle, adding a reactant will cause the equilibrium

to shift in the direction that consumes the added reactant.



Step 2: In this reaction, CO is a reactant. Adding more CO will drive the

equilibrium to the right to consume the additional CO, so the equilibrium

will shift to the right.



Step 1: Consider the effect of increasing the temperature on an exother-

mic reaction. According to Le Chatelier’s principle, increasing the tem-

perature in an exothermic reaction will favor the endothermic direction.



Step 2: In this case, the forward reaction is the exothermic direction

(2CO(g) + O2(g)→2CO2(g)). Therefore, increasing the temperature will

favor the reverse reaction to consume the excess heat. So, the equilibrium

will shift to the left.

Question 28

Question

Consider the following reaction at equilibrium:

N2(g) + 3H2(g)⇌2NH3(g)

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

the equilibrium will shift and explain why.

Solution

To determine the direction in which the equilibrium will shift when the tem-

perature is increased, we need to consider the effect of temperature on both the

reactants and products involved in the reaction.

Step 1: Exothermic Reaction

The given reaction is exothermic as the formation of NH3(g)releasesheat.T hismeansheatisaproductinthisreaction.

Step 2: Effect of Increasing Temperature

When the temperature is increased in an exothermic reaction, the system

will shift in the direction that consumes heat. This is in accordance with Le

Chatelier’s Principle, which states that a system at equilibrium will shift in a

way that counteracts the applied stress.

Step 3: Prediction

Since the forward reaction is exothermic (heat is a product in the forward

direction), increasing the temperature will cause the equilibrium to shift to-

wards the left (the direction that consumes heat) to counteract the increase in

temperature.

Therefore, the equilibrium will shift to favor the reactants (N2and H2) over

the products (NH3) when the temperature is increased.

Question 29

Question

Consider the reaction:

2SO2(g)+O2(g)⇌2SO3(g)

If the equilibrium constant, Kc, for this reaction is 4.5 at a certain temperature,

what will happen to the equilibrium position if the following changes are made:

a) The pressure is increased by decreasing the volume of the container. b)

Oxygen gas is removed from the reaction mixture. c) A catalyst is added to the

reaction mixture.

Solution

a) If the pressure is increased by decreasing the volume of the container, the

system will try to counteract the change according to Le Chatelier’s Principle.

Since there are more moles of gas on the left side of the equation, the system

will shift to the right to reduce the pressure.

b) Removing oxygen gas from the reaction mixture will disturb the equilib-

rium because it is a product in the forward reaction. According to Le Chatelier’s

Principle, the system will shift to the left to replace the lost oxygen gas, ulti-

mately producing more SO2and less SO3.

c) Adding a catalyst to the reaction mixture will not affect the equilibrium

position. A catalyst speeds up the rate of both the forward and reverse reactions

equally, so the ratio between products and reactants will remain the same.

Therefore, the equilibrium position will not be affected by the addition of a

catalyst.

Question 30

Question

Consider the reaction:

N2O4(g)⇌2NO2(g)

If the concentration of N2O4is increased at constant temperature, predict

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

Solution

To determine the direction in which the equilibrium will shift when the concen-

tration of N2O4is increased at constant temperature in the reaction:

N2O4(g)⇌2NO2(g)

we need to consider Le Chatelier’s Principle. This principle states that if a

system at equilibrium is subjected to a stress, the system will adjust itself in

order to partially offset the effect of that stress.

Step 1: Increase in concentration of N2O4

Increasing the concentration of N2O4will cause the system to adjust itself

by consuming some of the added N2O4to maintain equilibrium. The reaction

will shift to the right to consume N2O4and produce more NO2.

Therefore, the equilibrium will shift to the right, favoring the formation of

more NO2, to partially offset the increase in concentration of N2O4.

Question 31

Question

Consider the following reaction at equilibrium:

N2O4(g)⇌2NO2(g)

If an external pressure is applied to the system by decreasing the volume of

the container, predict how the equilibrium will shift according to Le Chatelier’s

Principle. Justify your answer with an explanation.

Solution

Step 1: When the volume of the container is decreased by applying external

pressure, the system will shift in the direction that reduces the total number of

gas molecules. This is because reducing the volume increases the pressure, and

the system will respond by shifting to counteract the increase in pressure.

Step 2: In the given reaction, N2O4has one gas molecule, while 2NO2has

two gas molecules. Therefore, the side with the fewer gas molecules is favored

when the pressure is increased.

Step 3: Thus, when the volume of the container is decreased by applying ex-

ternal pressure, the equilibrium will shift to the left (towards N2O4) to decrease

the total number of gas molecules and relieve the pressure.

Step 4: In summary, according to Le Chatelier’s Principle, when the volume

of the container is decreased, the equilibrium will shift to the left, favoring the

formation of N2O4to reduce the total number of gas molecules in the system.

Question 32

Question

Consider the reaction:

H2O(g)⇌H2O(l)

which has an equilibrium constant of Kc= 1.0×10−4at a certain temperature.

If the volume of the system is suddenly decreased, predict the direction in which

the equilibrium will shift and explain your reasoning.

Solution

Step 1: Determine the effect of changing the volume on the equilibrium. When

the volume of the system is decreased, the system will try to counteract the

change in pressure by shifting the equilibrium in the direction that reduces the

number of moles of gas.

Step 2: Analyze the number of moles of gas in the reaction. On the reactant

side, there are no moles of gas present, as both gaseous and liquid water do not

contribute to the pressure. On the product side, there is only one mole of liquid

water.

Step 3: Determine the direction of the equilibrium shift. Since there are

no moles of gas on the reactant side, reducing the volume will not affect the

system’s pressure. Therefore, the equilibrium will shift to the right (towards

the product side) to decrease the number of moles of gas.

Step 4: Write the equilibrium expression to justify the reasoning. The equi-

librium expression for the reaction is:

Kc=[H2O(l)]

[H2O(g)]

Since the concentration of liquid water is constant (pure liquid), the equilibrium

expression simplifies to:

Kc=[H2O(l)]

1= [H2O(l)]

Since the equilibrium constant is small (Kc= 1.0×10−4), the concentration of

liquid water is relatively low. Therefore, the equilibrium will shift to the right

to increase the concentration of liquid water.

Thus, the equilibrium will shift to the right (towards the formation of liquid

water) when the volume of the system is suddenly decreased.

Question 33

Question

Consider the following reaction:

H2O(g)⇌H2O(l)

If the volume of the container is suddenly decreased, explain how the equi-

librium shifts in response, according to Le Chatelier’s Principle.

Solution

To determine how the equilibrium of the reaction shifts in response to a sud-

den decrease in volume, we must consider the change in concentration of the

substances and the effect on the reaction’s equilibrium constant.

Step 1: Decrease in Volume When the volume of a container is suddenly

decreased, the pressure inside the container increases.

Step 2: Application of Le Chatelier’s Principle According to Le Chatelier’s

Principle, in response to the increase in pressure, the equilibrium will shift to

counteract the stress. In this case, because the number of gas molecules on the

left side of the reaction is greater than on the right side, the system will favor

the side with fewer gas molecules to decrease the pressure.

Step 3: Shift in Equilibrium Therefore, the equilibrium will shift towards

the right to decrease the total number of gas molecules. This results in an

increase in the concentration of liquid water and a decrease in the concentration

of water vapor.

Step 4: Conclusion In summary, when the volume of the container is sud-

denly decreased, the equilibrium shifts to the right to counteract the increase

in pressure, favoring the formation of liquid water over water vapor.

Question 34

Question

Consider the following reaction at equilibrium:

2 SO2(g)+ O2(g)⇌2 SO3(g)

If the pressure is increased by compressing the system, predict the direction

in which the equilibrium will shift. Justify your answer using Le Chatelier’s

Principle.

Solution

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

jected to a change in concentration, temperature, volume, or pressure, the equi-

librium will shift to counteract the imposed change.

Step 2: When the pressure of the system is increased by compressing it, the

system will respond by shifting the equilibrium in the direction that reduces the

total number of moles of gas present in the system.

Step 3: In the given reaction, there are a total of 3 moles of gas on the left

side (2 ×SO2+ O2) and 2 moles of gas on the right side (2 ×SO3).

Step 4: By compressing the system, the equilibrium will shift towards the

side with fewer moles of gas to alleviate the increase in pressure. Thus, the

equilibrium will shift to the right (towards the products) to decrease the total

number of gas molecules and reduce the pressure.

Step 5: Therefore, by compressing the system, the equilibrium will shift to

the right to generate more SO3and consume SO2and O2.

Question 35

Question

Consider the reaction:

N2(g) + 3H2(g) ⇌2NH3(g)

If the concentration of N2 gas is increased at constant temperature and

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

Chatelier’s Principle. Justify your answer.

Solution

Step 1: Increase in N2 concentration will shift the equilibrium to the right to

counteract the change. According to Le Chatelier’s Principle, an increase in the

concentration of a reactant will result in the equilibrium position shifting in the

direction that consumes some of that reactant.

Step 2: The reaction involves N2 and NH3, so the reaction will shift to the

right, favoring the formation of more NH3.

Step 3: The reaction is endothermic, as indicated by the positive heat of

formation for NH3. Increasing the concentration of N2 will shift the equilibrium

to the right, consuming more N2 and forming more NH3 to partially offset the

increase in N2 concentration.

Step 4: Therefore, the equilibrium will shift to the right, favoring the for-

mation of more NH3, to counteract the increase in N2 concentration.

Question 2

Question

Consider the reaction:

2 NO(g)+ Br2(g)⇌2 NOBr(g)

If the equilibrium constant, Kc, for the reaction at 500 K is 0.075, predict the

direction in which the reaction will shift if the pressure is increased at constant

temperature.

Solution

Le Chatelier’s Principle states that if a system at equilibrium is perturbed by a

change in conditions, the equilibrium will shift to counteract the change.

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

- Since there are 3 moles of gas on the left side of the reaction and only 2

moles of gas on the right side, increasing the pressure will cause the reaction to

shift to the side with fewer moles of gas to reduce the pressure.

Step 2: Determine the initial reaction quotient, Qc.

- The initial reaction quotient, Qc, is calculated using the same expression as

the equilibrium constant, but with initial concentrations instead of equilibrium

concentrations.

Qc=[NOBr]2

[NO]2·[Br2]

Step 3: Compare Qcto Kc.

- If Qc< Kc, the reaction will shift to the right to produce more products.

- If Qc> Kc, the reaction will shift to the left to produce more reactants.

Step 4: Predict the direction of the reaction shift.

- Since the initial reaction mixture contains no products (NOBr), Qc= 0. -

Since Qc< Kc, the reaction will shift to the right to produce more NOBr and

reach equilibrium.

Therefore, if the pressure is increased at 500 K, the reaction will shift to the

right to produce more NOBr in order to decrease the pressure back to its initial

value.

Question 3

Question

Consider the following reaction at equilibrium:

2SO2(g)+O2(g)⇌2SO3(g)

If the concentration of SO2is increased, predict the direction in which the

equilibrium will shift and explain why using Le Chatelier’s Principle.

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, temperature, or pressure),

the system will react in a way that opposes the stress.

Step 2: In this case, by increasing the concentration of SO2, the system will

sense an excess of SO2molecules and will try to use up some of them to establish

a new equilibrium.

Step 3: Therefore, the equilibrium will shift to the right, towards the forma-

tion of more SO3molecules, in order to decrease the concentration of SO2back

to the original equilibrium level.

Step 4: As a result of the shift to the right, the concentration of SO3will

increase, while the concentrations of SO2and O2will decrease.

Step 5: This shift ultimately helps to counteract the increase in SO2con-

centration and restore the equilibrium position of the reaction.

Question 4

Question

Consider the following equilibrium:

2 SO2(g) + O2(g) ⇌2 SO3(g)

If the equilibrium mixture is disturbed by increasing the pressure, predict

the direction in which the equilibrium will shift and justify your answer.

Solution

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

Increasing the pressure will shift the equilibrium towards the side with fewer

gas molecules to reduce the pressure.

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

equilibrium.

Initially, there are 3 gas molecules on the left side ((2 ×SO2)+O2) and 2

gas molecules on the right side (2 ×SO3).

Step 3: Compare the total number of gas molecules on each side.

Since there are fewer gas molecules on the right side of the equilibrium, an

increase in pressure will cause the equilibrium to shift towards the right side to

reduce the pressure.

Step 4: Write the equilibrium expression for the reaction.

The equilibrium expression for the reaction is given by:

K=[SO3]2

[SO2]2[O2]

Step 5: Justify the direction in which the equilibrium will shift.

The equilibrium will shift to the right to decrease the total number of gas

molecules and reduce the pressure, favoring the formation of more SO3.

Therefore, the equilibrium will shift to the right if the pressure is increased.

Question 5

Question

Consider the reaction:

2NOCl(g)⇌2NO(g) + Cl2(g)

If the volume of the reaction vessel is suddenly decreased, predict the direc-

tion of shift for this equilibrium reaction according to Le Chatelier’s Principle.

Provide a detailed explanation for your choice.

Solution

To analyze the effect of a sudden decrease in volume on this equilibrium reaction,

we should consider the changes in pressure and concentrations of the reactants

and products.

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

inside the vessel increases since the number of gas molecules in the system

remains constant.

Step 2: According to Le Chatelier’s Principle: - An increase in pressure

will cause the system to shift in a direction that reduces the total number of gas

molecules. - A decrease in pressure will cause the system to shift in a direction

that increases the total number of gas molecules.

Step 3: In this given reaction, there are 3 moles of gas on the left side (2

moles of NOCl and 1 mole of Cl2) and 4 moles of gas on the right side (2 moles

of NO).

Step 4: Since the volume is decreased, pressure is increased. To reduce

the pressure, the system will shift in the direction of more moles of gas, which

means the equilibrium position will shift towards the right side of the reaction

to increase the concentration of gas molecules.

Step 5: Therefore, in response to the sudden decrease in volume, the equi-

librium will shift to the right, favoring the formation of more NO and Cl2from

NOCl.

Question 6

Question

Consider the following equilibrium reaction:

2SO2(g)+ O2(g)⇌2SO3(g)

If the concentration of SO2(g)is increased while maintaining the volume and

temperature constant, 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

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

will adjust to counteract the change and restore equilibrium.

Step 2: In this case, if the concentration of SO2(g)is increased, the system

will react in such a way as to counteract the change. Since SO2(g)is a reactant in

the forward reaction, increasing its concentration will drive the reaction towards

the products side to consume the excess reactant.

Step 3: Therefore, the equilibrium will shift to the right, producing more

SO3(g)until a new equilibrium is established.

Step 4: In conclusion, an increase in the concentration of SO2(g)will cause

the equilibrium to shift towards the products side to partially alleviate the

increase in SO2(g)concentration.

Question 7

Question

Consider the following equilibrium reaction:

N2O4(g)⇌2NO2(g)

If the concentration of N2O4is increased at constant temperature, describe how

the system will respond based on Le Chatelier’s Principle.

Solution

To determine how the system will respond when the concentration of N2O4is

increased at constant temperature, we can analyze Le Chatelier’s Principle.

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

reactant is increased, the system will shift to consume the added reactant. In

this case, increasing the concentration of N2O4will cause the reaction to shift

to the right to consume more N2O4.

Step 2: By shifting to the right, more N2O4will be consumed, producing

more NO2until a new equilibrium is established.

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

to an increase in the concentration of NO2and a decrease in the concentration

of N2O4to partially offset the increase in N2O4concentration.

Therefore, when the concentration of N2O4is increased at constant tem-

perature, the system will shift to the right to consume more N2O4until a new

equilibrium is reached.

Question 8

Question

Consider the following reaction at equilibrium:

2 SO2(g)+O2(g)⇌2 SO3(g)

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

the left, right, or remain unchanged? Justify your answer using Le Chatelier’s

Principle.

Solution

To determine the effect of an increase in temperature on the equilibrium position

of the given reaction, we need to consider Le Chatelier’s Principle. This principle

states that if a system at equilibrium is subjected to a stress, the system will

adjust itself in order to counteract the effect of that stress.

Step 1: Reaction Quotient First, let’s write the equilibrium constant ex-

pression for the reaction:

Keq =[SO3]2

[SO2]2×[O2]

Step 2: Effect of Increase in Temperature An increase in temperature is a

stress on the system. In this case, the reaction is exothermic (negative change in

enthalpy), meaning the forward reaction is favored by a decrease in temperature.

Therefore, an increase in temperature will be considered a stress that the system

will try to counteract.

Step 3: Shift in Equilibrium To counteract the increase in temperature,

the equilibrium will shift in the endothermic direction to absorb the extra heat.

This means the equilibrium will shift to the left (towards the reactants) in order

to consume heat.

Therefore, the equilibrium will shift to the left when the temperature of the

system is increased.

Question 9

Question

Consider the following reaction at equilibrium:

2SO2(g)+O2(g)⇌2SO3(g)

If the temperature is increased, predict the direction in which the equilibrium

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

Solution

Step-by-step solution:

Step 1: When the temperature is increased, the system will attempt to coun-

teract this change. In this case, since the reaction is exothermic (produces heat),

adding heat to the system will cause the equilibrium to shift in the direction

that consumes the excess heat.

Step 2: In the given reaction, the forward reaction is exothermic (heat is a

product). Therefore, increasing the temperature will cause the reaction to shift

in the reverse direction to consume the excess heat.

Step 3: As a result, when the temperature is increased, the equilibrium will

shift to the left, favoring the formation of more reactants (2SO2and O2)andreducingtheformationofproducts(2SO3).

Question 10

Question

Consider the following equilibrium reaction:

2 SO2(g)+O2(g)⇌2 SO3(g) + 118 kJ/mol

If the concentration of O2(g) is increased, predict the direction in which the

equilibrium will shift according to Le Chatelier’s Principle.

Solution

Step 1: When the concentration of O2(g) is increased, the system will try to

counteract this change by shifting the equilibrium to the side that consumes

O2(g). In this case, the forward reaction consumes O2(g), so the equilibrium

will shift to the right.

Step 2: By shifting to the right, more SO3(g) will be formed.

Therefore, according to Le Chatelier’s Principle, if the concentration of O2(g)

is increased, the equilibrium will shift to the right to produce more SO3(g).

Question 11

Question

Consider the following equilibrium reaction:

N2O4(g)⇌2NO2(g)

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

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

Principle. Justify your answer.

Solution

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

increased by decreasing the volume, we need to analyze the changes caused by

the pressure increase and apply Le Chatelier’s Principle.

Step 1: Identify the effect of the pressure change on the equi-

librium system. When the volume of the system is decreased, the pressure

will increase. According to Le Chatelier’s Principle, the system will respond by

shifting the equilibrium to counteract this change.

Step 2: Determine the reaction that will alleviate the increase in

pressure. In this case, decreasing the volume increases the pressure, so the

system will want to reduce the total number of particles in order to decrease

the pressure.

Step 3: Analyze the stoichiometry of the reaction. In the given

reaction, one mole of N2O4 gas dissociates to form two moles of NO2 gas.

Therefore, the total number of moles of gas will decrease when N2O4 dissociates

to form NO2.

Step 4: Apply Le Chatelier’s Principle. To decrease the pressure

caused by the volume decrease, the equilibrium will shift in the direction that

reduces the total number of gas molecules. In this case, the equilibrium will

shift to the left to decrease the pressure. This means that more N2O4 will be

formed at equilibrium.

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

equilibrium will shift towards the left to favor the formation of more N2O4 gas

molecules and alleviate the pressure increase.

Question 12

Question

Consider the equilibrium reaction:

2AB(g)⇌A2(g) + B2(g)

If the volume of the container is decreased, predict the direction in which the

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

with an explanation.

Solution

Step 1: When the volume of the container is decreased, the system will try to

counteract the change by shifting the equilibrium in a direction that will relieve

the stress caused by the volume change.

Step 2: The volume decrease causes the pressure to increase. According to

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

total number of gas molecules so that the pressure can decrease.