LeChatelier's Principle

The LeChatelier's Principle Concept Builder is comprised of 54 questions. The questions are divided into 18 different Question Groups and spread across three difficulty levels. Questions in the same group have identical types of stresses. The Concept Builder is coded to select at random a question from each group until a student is successful with that group of questions.

There are three difficulty levels that can be engaged in through the Concept Builder. Those three difficulty levels are differentiated as follows:
 

• Apprentice Difficulty Level: Question Groups 1-4 ... The chemical equation for a reversible system is given. A particular stress is identified; the stress will either be the addition or removal of a gaseous- or aqueous-state reactant or product. Learners must identify the direction that the equilibrium will shift in response to the stress.
• Master Difficulty Level: Question Groups 5-12 ... The chemical equation for a reversible system is given. A particular stress is identified. The stress will either be the addition or removal of a reactant or product or an increase or a decrease in the pressure or temperature. Learners must identify the direction that the equilibrium will shift in response to the stress.
• Wizard Difficulty Level: Question Groups 13-18 ... The chemical equation for a reversible system is given. A particular stress is identified. The stress will either be the addition or removal of a gaseous- or aqueous-state reactant or product or an increase or a decrease in the pressure or temperature. Learners must identify the direction that the equilibrium will shift in response to the stress. They must also idenitfy how this shift will affect the amount of a particular reactant or product present in the system.

The questions from each group are shown below. Teachers are encouraged to view the questions in order to judge which difficulty levels are most appropriate for their classes. We recommend providing students two or more options. 

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LeChatelier's Principle

 
Apprentice Difficulty Level
Question Group 1
Question 1
The following reversible system is at equilibrium:
 

CO _(g)   +    H₂O _(g)    «    H_{2 (g)}   +    CO_{2 (g)}

 
If additional carbon monoxide (CO) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
Question 2
The following reversible system is at equilibrium:
 

2 SO_3 (g)   «    2 SO_2 (g)   +    O_2 (g)

 
If additional sulfur trioxide (SO₃) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
Question 3
The following reversible system is at equilibrium:
 

PCl_{5 (g)}    «    PCl_{3 (g)}   +    Cl_{2 (g)}

 
If additional phosphorus pentachloride (PCl₅) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 
Question Group 2
Question 4
The following reversible system is at equilibrium:
 

CO _(g)   +    H₂O _(g)    «    H_{2 (g)}   +    CO_{2 (g)}

 
If some carbon monoxide (CO) is removed from the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

Question 5
The following reversible system is at equilibrium:
 

2 SO_3 (g)   «    2 SO_2 (g)   +    O_2 (g)

 
If some sulfur trioxide (SO₃) is removed from the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

Question 6
The following reversible system is at equilibrium:
 

PCl_{5 (g)}    «    PCl_{3 (g)}   +    Cl_{2 (g)}

 
If some phosphorus pentachloride (PCl₅) is removed from the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 

 
Question Group 3
Question 7
The following reversible system is at equilibrium:
 

CO _(g)   +    H₂O _(g)    «    H_{2 (g)}   +    CO_{2 (g)}

 
If additional carbon dioxide (CO₂) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

Question 8
The following reversible system is at equilibrium:
 

2 SO_3 (g)   «    2 SO_2 (g)   +    O_2 (g)

 
If additional sulfur dioxide (SO₂) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 

 
Question 9
The following reversible system is at equilibrium:
 

PCl_{5 (g)}    «    PCl_{3 (g)}   +    Cl_{2 (g)}

 
If additional phosphorus trichloride (PCl₃) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 

 
Question Group 4
Question 10
The following reversible system is at equilibrium:
 

CO _(g)   +    H₂O _(g)    «    H_{2 (g)}   +    CO_{2 (g)}

 
If some carbon dioxide (CO₂) is removed from the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 

 
Question 11
The following reversible system is at equilibrium:
 

2 SO_3 (g)   «    2 SO_2 (g)   +    O_2 (g)

 
If some sulfur dioxide (SO₂) is removed from the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

Question 12
The following reversible system is at equilibrium:
 

PCl_{5 (g)}    «    PCl_{3 (g)}   +    Cl_{2 (g)}

 
If some phosphorus trichloride (PCl₃) is removed from the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

 
 
Master Difficulty Level
Question Group 5
Question 13
The following reversible system is at equilibrium:
 

C_(s)    +   CO_{2 (g)}    «    2 CO_(g)

 
If additional carbon dioxide (CO₂) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 


 
Question 14
The following reversible system is at equilibrium:
 

C_(s)    +   CO_{2 (g)}    «    2 CO_(g)

 
If additional carbon monoxide (CO) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 

 
Question 15
The following reversible system is at equilibrium:
 

C_(s)    +   CO_{2 (g)}    «    2 CO_(g)

 
If some carbon monoxide (CO) is removed from the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

 
 
Question Group 6
Question 16
The following reversible system is at equilibrium:
 

2 H₂O _(l)      «    2 H_{2 (g)}    +    O_{2 (g)}

 
If additional hydrogen (H₂) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 

 
Question 17
The following reversible system is at equilibrium:
 

2 H₂O _(l)     «    2 H_{2 (g)}    +    O_{2 (g)}

 
If additional oxygen (O₂) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 

 
Question 18
The following reversible system is at equilibrium:
 

2 H₂O _(l)      «    2 H_{2 (g)}    +    O_{2 (g)}

 
If some hydrogen (H₂) is removed from the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 

 
Question Group 7
Question 19
The following reversible system is at equilibrium:
 

P_{4 (s)}    +    6 Cl_{2 (g)}    «    4 PCl_{3 (l)}

 
If additional phosphorus (P₄) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 


 
Question 20
The following reversible system is at equilibrium:
 

P_{4 (s)}    +    6 Cl_{2 (g)}    «    4 PCl_{3 (l)}

 
If additional phosphorus trichloride (PCl₃) is added to the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 
Question 21
The following reversible system is at equilibrium:
 

P_{4 (s)}    +    6 Cl_{2 (g)}    «    4 PCl_{3 (l)}

 
If some phosphorus (P₄) is removed from the system, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 

 
Question Group 8
Question 22
The following reversible system is at equilibrium:
 

N_{2 (g)}    +   3 H_{2 (g)}    «    2 NH_3(g)

 
If the pressure of the system were increased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

Question 23
The following reversible system is at equilibrium:
 

N₂O_{4 (g)}    «    2 NO_{2 (g)}

 
If the pressure of the system were increased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

Question 24
The following reversible system is at equilibrium:
 

4 NO_2(g)    +   6 H₂O_(g)   «    4 NH_{3 (g)}    +    7 O_{2 (g)}

 
If the pressure of the system were increased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 
 


Question Group 9
Question 25
The following reversible system is at equilibrium:
 

N_{2 (g)}    +   3 H_{2 (g)}    «    2 NH_3(g)

 
If the pressure of the system were decreased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

Question 26
The following reversible system is at equilibrium:
 

2 NO_{2 (g)}    «    N₂O_{4 (g)}    

 
If the pressure of the system were decreased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 

 
Question 27
The following reversible system is at equilibrium:
 

4 NO_2(g)    +   6 H₂O_(g)   «    4 NH_{3 (g)}    +    7 O_{2 (g)}

 
If the pressure of the system were decreased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 
 
Question Group 10
Question 28
The following reversible system is at equilibrium:
 

CO _(g)   +    H₂O _(g)    «    H_{2 (g)}   +    CO_{2 (g)}

 
If the pressure of the system were increased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

Question 29
The following reversible system is at equilibrium:
 

H_{2 (g)}    +   F_{2 (g)}    «    2 HF _(g)

 
If the pressure of the system were increased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 

 
Question 30
The following reversible system is at equilibrium:
 

NO _(g)   +    O_3 (g)   «    NO_2 (g)   +    O_2 (g)

 
If the pressure of the system were decreased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 

 
Question Group 11
Question 31
The following reversible system is at equilibrium:
 

N_{2 (g)}    +   3 H_{2 (g)}    «    2 NH_3(g)
∆H = -92 kJ

 
If the temperature of the system were increased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 

 
Question 32
The following reversible system is at equilibrium:
 

N₂O_{4 (g)}    «    2 NO_{2 (g)}    
∆H = +58 kJ

 
If the temperature of the system were increased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 

 
Question 33
The following reversible system is at equilibrium:
 

2 SO_2 (g)   +    O_2 (g)     «    2 SO_3 (g)
∆H = -198 kJ

 
If the temperature of the system were increased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 
 

 
Question Group 12
Question 34
The following reversible system is at equilibrium:
 

N_{2 (g)}    +   3 H_{2 (g)}    «    2 NH_3(g)
∆H = -92 kJ

 
If the temperature of the system were decreased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

Question 35
The following reversible system is at equilibrium:
 

N₂O_{4 (g)}    «    2 NO_{2 (g)}    
∆H = +58 kJ

 
If the temperature of the system were decreased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 

Question 36
The following reversible system is at equilibrium:
 

2 SO_2 (g)   +    O_2 (g)     «    2 SO_3 (g)
∆H = -198 kJ

 
If the temperature of the system were decreased, then the equilibrium position would ______.
not be affected by such a change
shift to the right in the direction of products
shift to the left in the direction of reactants
 
 


 
 
 
Wizard Difficulty Level
Question Group 13
Question 37
The following reversible system is at equilibrium:
 

2 NO _(g)    +   Cl_{2 (g)}    «    2 NOCl _(g)

 
If additional Cl₂ were added to the system, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of NO would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of NOCl would ________.
a. increase                            b. decrease                          c. remain unchanged
 

 
Question 38
The following reversible system is at equilibrium:
 

PCl_{3 (g)}    +    3 NH_{3 (g)}    «    P(NH₂)_{3 (g)}    +    3 HCl_(g)

 
If additional P(NH₂)₃ were added to the system, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of NH₃ would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of HCl would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

Question 39
The following reversible system is at equilibrium:
 

4 NH_{3 (g)}    +   7 O_{2 (g)}    «    4 NO_2(g)    +    6 H₂O_(g)

 
If additional H₂O were added to the system, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of NH₃would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of NO₂would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

 
 
Question Group 14
Question 40
The following reversible system is at equilibrium:
 

2 NO _(g)    +   Cl_{2 (g)}    «    2 NOCl _(g)

 
If some Cl₂were removed from the system, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of NOwould ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of NOClwould ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

Question 41
The following reversible system is at equilibrium:
 

PCl_{3 (g)}    +    3 NH_{3 (g)}    «    P(NH₂)_{3 (g)}    +    3 HCl_(g)

 
If some P(NH₂)₃were removed from the system, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of NH₃would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of HClwould ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

Question 42
The following reversible system is at equilibrium:

4 NH_{3 (g)}    +   7 O_{2 (g)}    «    4 NO_2(g)    +    6 H₂O_(g)

 
If some H₂O were removed from the system, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of NH₃would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of NO₂would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 
 

 
Question Group 15
Question 43
The following reversible system is at equilibrium:

COCl_{2 (g)}    «    CO _(g)    +   Cl_{2 (g)}

 
If the pressure of the system were increased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of COCl₂would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of COwould ________.
a. increase                            b. decrease                          c. remain unchanged
 

 
Question 44
The following reversible system is at equilibrium:

2 NO _(g)    +   Cl_{2 (g)}    «    2 NOCl _(g)

 
If the pressure of the system were increased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of NO would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of NOCl would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

Question 45
The following reversible system is at equilibrium:

2 SO_3 (g)   «    2 SO_2 (g)   +    O_2 (g)

 
If the pressure of the system were increased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of SO₃ would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of SO₂ would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 
 

 
Question Group 16
Question 46
The following reversible system is at equilibrium:

COCl_{2 (g)}    «    CO _(g)    +   Cl_{2 (g)}

 
If the pressure of the system were decreased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of COCl₂would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of COwould ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

Question 47
The following reversible system is at equilibrium:

2 NO _(g)    +   Cl_{2 (g)}    «    2 NOCl _(g)

 
If the pressure of the system were decreased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of NO would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of NOCl would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

Question 48
The following reversible system is at equilibrium:

2 SO_3 (g)   «    2 SO_2 (g)   +    O_2 (g)

 
If the pressure of the system were decreased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of SO₃ would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of SO₂ would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

 
 
Question Group 17
Question 49
The following reversible system is at equilibrium:

2 SO_2 (g)   +    O_2 (g)     «    2 SO_3 (g)
∆H = -198 kJ

If the temperature of the system were increased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of SO₂ would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of SO₃ would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

Question 50
The following reversible system is at equilibrium:

NO _(g)   +    O_3 (g)   «    NO_2 (g)   +    O_2 (g)
∆H = -199 kJ

 
If the temperature of the system were increased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of NO would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of NO₂ would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

Question 51
The following reversible system is at equilibrium:

2 H₂O _(l)      «    2 H_{2 (g)}    +    O_{2 (g)}
∆H = + 286 kJ

 
If the temperature of the system were increased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of H₂ would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of O₂would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 
 
 

 
Question Group 18
Question 52
The following reversible system is at equilibrium:

2 SO_2 (g)   +    O_2 (g)     «    2 SO_3 (g)
∆H = -198 kJ

 
If the temperature of the system were decreased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of SO₂ would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of SO₃ would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

Question 53
The following reversible system is at equilibrium:

NO _(g)   +    O_3 (g)   «    NO_2 (g)   +    O_2 (g)
∆H = -199 kJ

 
If the temperature of the system were decreased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of NO would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of NO₂ would ________.
a. increase                            b. decrease                          c. remain unchanged
 
 

Question 54
The following reversible system is at equilibrium:

2 H₂O _(l)      «    2 H_{2 (g)}    +    O_{2 (g)}
∆H = + 286 kJ

 
If the temperature of the system were decreased, then the equilibrium position would ______.
a. shift to the right               b. shift to the left                  c. not shift at all
 
The result is that the amount of H₂ would ________ ...
a. increase                            b. decrease                          c. remain unchanged
 
... and the amount of O₂would ________.
a. increase                            b. decrease                          c. remain unchanged