Chemical Equilibrium Practice Questions
Thanaweya Amma (Egypt) · Thanaweya Chemistry · 151 free MCQs with instant results and detailed explanations.
151
Total
46
Easy
75
Medium
30
Hard
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Sample Questions from Chemical Equilibrium
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Q1
Easy
What is the principle that states that if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will adjust to counteract that change?
A.
Hess's Law
B.
Le Chatelier's Principle
C.
Raoult's Law
D.
Dalton's Law
Show Answer & Explanation
Correct Answer: B
Le Chatelier's Principle describes how a system at equilibrium responds to changes in conditions. It states that the system will shift in a direction that counteracts the imposed change.
Q2
Easy
In a certain reversible reaction, the equilibrium concentrations at 25°C are [A] = 0.4 M, [B] = 0.2 M, and [C] = 0.1 M. What is the equilibrium constant (Kc) for this reaction if the reaction is A ⇌ B + C?
A.
0.5
B.
2.0
C.
4.0
D.
0.25
Show Answer & Explanation
Correct Answer: B
The equilibrium constant Kc is calculated using the formula Kc = [B][C] / [A]. Substituting the values gives Kc = (0.2)(0.1) / (0.4) = 0.02 / 0.4 = 0.5, which simplifies to Kc = 2.0.
Q3
Easy
If the temperature of an exothermic equilibrium reaction is increased, what will likely happen to the position of the equilibrium?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase the rate of reaction
Show Answer & Explanation
Correct Answer: B
For an exothermic reaction, increasing the temperature will shift the equilibrium to the left, favoring the reactants. This is in accordance with Le Chatelier's Principle, where the system reacts to absorb the added heat.
Q4
Medium
For the equilibrium reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), which of the following statements is true when the system is at equilibrium?
A.
The rate of formation of SO2 equals the rate of consumption of SO3.
B.
The concentration of SO3 remains constant over time.
C.
The total pressure in the system decreases.
D.
All reactants are completely converted to products.
Show Answer & Explanation
Correct Answer: B
At equilibrium, the concentrations of reactants and products remain constant, indicating that the formation of SO3 is equal to its decomposition.
Q5
Medium
In a closed container at equilibrium, the concentration of reactants is 0.2 M and that of products is 0.8 M for the reaction A ⇌ B. What is the equilibrium constant Kc?
A.
4.0
B.
2.0
C.
0.5
D.
1.0
Show Answer & Explanation
Correct Answer: A
The equilibrium constant Kc is calculated as Kc = [B]/[A] = 0.8/0.2 = 4.0, indicating a strong favoring of products.
Q6
Medium
Which factor does not affect the position of equilibrium for the reaction CO(g) + 2H2(g) ⇌ CH3OH(g)?
A.
Change in temperature
B.
Change in pressure
C.
Addition of a catalyst
D.
Change in concentration of reactants
Show Answer & Explanation
Correct Answer: C
A catalyst speeds up the rate of reaching equilibrium but does not change the position of equilibrium itself.
Q7
Medium
When the reaction PCl5(g) ⇌ PCl3(g) + Cl2(g) reaches equilibrium, which of the following conditions will result in a decrease of PCl5 concentration?
A.
Decrease in volume of the container
B.
Increase in temperature
C.
Add more PCl3
D.
Decrease in Cl2 concentration
Show Answer & Explanation
Correct Answer: C
Adding more PCl3 shifts the equilibrium left, leading to a decrease in PCl5 concentration as the reaction compensates for the increase.
Q8
Hard
In a closed system at dynamic equilibrium, if the temperature is increased, which of the following will occur if the reaction is exothermic?
A.
The formation of products increases.
B.
The formation of reactants increases.
C.
The equilibrium constant decreases.
D.
The reaction rate remains unchanged.
Show Answer & Explanation
Correct Answer: B
According to Le Chatelier's principle, if the temperature of an exothermic reaction is increased, the equilibrium shifts to the left, favoring the formation of reactants to absorb the excess heat.
Q9
Hard
At 25°C, the equilibrium constant Kc for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) is 0.5. If the initial concentrations are [N2] = 0.4 M, [H2] = 0.9 M, and [NH3] = 0.1 M, what will be the direction of the shift in equilibrium?
A.
Shift to the right
B.
Shift to the left
C.
No shift
D.
Equilibrium is reached
Show Answer & Explanation
Correct Answer: B
To determine the direction of equilibrium shift, calculate the reaction quotient Q. Here, Q = [NH3]^2 / ([N2][H2]^3) = (0.1)^2 / (0.4 * (0.9)^3) = 0.016. Since Q < Kc (0.5), the equilibrium will shift to the left to increase reactants.
Q10
Hard
In a closed system at equilibrium, the concentration of reactants is 0.2 M and the concentration of products is 0.5 M for the reaction A + B ⇌ C + D. What is the equilibrium constant (Kc) for this reaction?
A.
2.5
B.
0.4
C.
0.8
D.
1.2
Show Answer & Explanation
Correct Answer: A
The equilibrium constant Kc is calculated as Kc = [C][D]/[A][B]. Here, Kc = (0.5)(0.5)/(0.2)(0.2) = 2.5, thus the correct answer is A.
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Chemical Equilibrium — Thanaweya Amma (Egypt) Thanaweya Chemistry Practice Questions Online
This page contains 151 practice MCQs for the chapter Chemical Equilibrium in Thanaweya Amma (Egypt) Thanaweya Chemistry. The questions are organized by difficulty — 46 easy, 75 medium, 30 hard — so you can choose the right level for your preparation.
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