chemistry : class11 Le Chatelier’s Principle : Equilibrium in chemical processes : Equilibrium MCQ Questions and Answers
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Le Chatelier’s Principle
MCQ questions and answers.
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MCQ Questions
1. According to Le Chatelier’s principle, what happens when the concentration of a reactant is increased in an equilibrium reaction?
A.
The equilibrium shifts toward the reactants
B.
The equilibrium shifts toward the products
C.
The equilibrium stops permanently
D.
The equilibrium constant becomes zero
Correct Answer:
The equilibrium shifts toward the products
Explanation:
The system shifts in the direction that consumes the added reactant, so the equilibrium moves toward the products.
2. For the equilibrium N2(g) + 3H2(g) ⇌ 2NH3(g), what is the effect of increasing pressure?
A.
The equilibrium shifts toward NH3
B.
The equilibrium shifts toward N2 and H2
C.
There is no change because gases are involved
D.
The reaction stops
Correct Answer:
The equilibrium shifts toward NH3
Explanation:
Increasing pressure favors the side with fewer gas molecules. There are 4 moles of gas on the reactant side and 2 moles on the product side, so the equilibrium shifts toward NH3.
3. For the equilibrium H2(g) + I2(g) ⇌ 2HI(g), what happens when pressure is increased?
A.
The equilibrium shifts toward H2 and I2
B.
The equilibrium shifts toward HI
C.
The equilibrium position does not change
D.
The equilibrium constant becomes larger
Correct Answer:
The equilibrium position does not change
Explanation:
Both sides contain the same total number of gas molecules, so changing pressure does not shift the equilibrium position.
4. In an exothermic equilibrium reaction, what is the effect of increasing temperature?
A.
The equilibrium shifts toward the products
B.
The equilibrium shifts toward the reactants
C.
The reaction becomes irreversible
D.
The equilibrium cannot be established
Correct Answer:
The equilibrium shifts toward the reactants
Explanation:
Heat acts like a product in an exothermic reaction. Increasing temperature causes the equilibrium to shift in the direction that consumes heat, toward the reactants.
5. In an endothermic equilibrium reaction, what happens when temperature is increased?
A.
The equilibrium shifts toward the reactants
B.
The equilibrium shifts toward the products
C.
The equilibrium position remains unchanged
D.
The reaction immediately stops
Correct Answer:
The equilibrium shifts toward the products
Explanation:
Heat acts like a reactant in an endothermic reaction. Increasing temperature favors the forward direction, so the equilibrium shifts toward the products.
6. What is the effect of adding more product to a system at equilibrium?
A.
The equilibrium shifts toward the products
B.
The equilibrium shifts toward the reactants
C.
The equilibrium disappears
D.
The reaction becomes faster in both directions permanently
Correct Answer:
The equilibrium shifts toward the reactants
Explanation:
The system opposes the addition of product by consuming some of it, so the equilibrium shifts toward the reactants.
7. What is the effect of removing a reactant from an equilibrium mixture?
A.
The equilibrium shifts toward the reactants
B.
The equilibrium shifts toward the products
C.
The equilibrium constant becomes zero
D.
The reaction becomes impossible
Correct Answer:
The equilibrium shifts toward the reactants
Explanation:
The system opposes the removal of a reactant by producing more of it, so the equilibrium shifts in the reverse direction.
8. What is the effect of adding a catalyst to a system already at equilibrium?
A.
The equilibrium shifts toward the products
B.
The equilibrium shifts toward the reactants
C.
The equilibrium position does not change
D.
The products are completely consumed
Correct Answer:
The equilibrium position does not change
Explanation:
A catalyst speeds up both the forward and reverse reactions equally. It helps the system reach equilibrium faster but does not shift the equilibrium position.
9. For the equilibrium CaCO3(s) ⇌ CaO(s) + CO2(g), what happens when the concentration of CO2 is increased?
A.
The equilibrium shifts toward CaCO3
B.
The equilibrium shifts toward CaO and CO2
C.
The equilibrium position does not change
D.
The solid CaCO3 immediately disappears
Correct Answer:
The equilibrium shifts toward CaCO3
Explanation:
The system consumes the added carbon dioxide by shifting in the reverse direction, toward calcium carbonate.
10. For the equilibrium 2SO2(g) + O2(g) ⇌ 2SO3(g), what happens when oxygen is removed?
A.
The equilibrium shifts toward SO3
B.
The equilibrium shifts toward SO2 and O2
C.
The equilibrium position remains unchanged
D.
The equilibrium reaction stops permanently
Correct Answer:
The equilibrium shifts toward SO2 and O2
Explanation:
The system opposes the removal of oxygen by producing more oxygen, so the equilibrium shifts toward the reactants.
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