Questions on Effect of Concentration, Temperature, and Pressure
Multiple-Choice Questions: Effect of Concentration, Temperature, and Pressure
1. What happens when the concentration of a reactant is increased in a reversible reaction?
A) Reaction stops
B) Equilibrium shifts to the left
C) Equilibrium shifts to the right
D) No effect
E) Equilibrium constant decreases
2. Which change causes equilibrium to shift toward the reactants?
A) Adding product
B) Removing product
C) Adding reactant
D) Increasing pressure
E) Increasing temperature in an endothermic reaction
3. For a gaseous reaction: 2NO₂(g) ⇌ N₂O₄(g), what happens when pressure increases?
A) Shift left
B) Shift right
C) No change
D) Increase in NO₂
E) Decrease in N₂O₄
4. In an exothermic reaction, what happens when temperature is increased?
A) Shift toward products
B) Shift toward reactants
C) No shift
D) Reaction speeds up but equilibrium remains
E) Reaction stops
5. If the concentration of a product is decreased, how does the system respond?
A) No change
B) Shift to the left
C) Shift to the right
D) Increase reactant concentration
E) K_eq decreases
6. What effect does adding an inert gas at constant volume have on equilibrium?
A) Shifts right
B) Shifts left
C) No effect
D) Increases yield
E) Decreases pressure
7. For the reaction: A(g) + B(g) ⇌ 2C(g), what happens if pressure is decreased?
A) Shift to left
B) Shift to right
C) No change
D) More product formed
E) Catalyst is used up
8. Which factor affects the value of the equilibrium constant (K_eq)?
A) Concentration
B) Catalyst
C) Pressure
D) Temperature
E) Volume
9. Which change will NOT affect the position of equilibrium?
A) Temperature change
B) Pressure change (in gases)
C) Concentration change
D) Catalyst addition
E) Removal of products
10. In a reaction with equal moles of gas on both sides, what is the effect of pressure change?
A) Shift left
B) Shift right
C) No shift
D) K_eq increases
E) Products decompose
11. In an endothermic reaction, increasing temperature causes:
A) A shift to the left
B) Decrease in reaction rate
C) Shift to the right
D) Reaction to stop
E) Lower yield of product
12. If a reactant is removed from a system at equilibrium, the system will:
A) Shift right
B) Shift left
C) Form more products
D) Not change
E) Increase temperature
13. How does decreasing temperature affect an exothermic reaction at equilibrium?
A) Shift to left
B) Shift to right
C) No change
D) Stops completely
E) Products decompose
14. What happens if the concentration of all species in a system is increased equally?
A) Equilibrium shifts left
B) Equilibrium shifts right
C) No shift in equilibrium position
D) K_eq changes
E) Catalyst is required
15. In a gaseous reaction, what does increasing volume do to equilibrium?
A) Acts like decreasing pressure
B) Acts like increasing pressure
C) Shifts to side with fewer moles
D) Shifts to side with liquids
E) Has no effect
16. Which of the following is true for changing pressure in solid–gas equilibrium?
A) Solids affect pressure significantly
B) Solids are unaffected and do not affect equilibrium
C) Pressure changes shift solid phase
D) Pressure increases product solids
E) Solids are always removed
17. In an endothermic reaction, decreasing temperature leads to:
A) More products
B) Reaction stopping
C) A shift to the left
D) Catalyst decomposition
E) No shift
18. If pressure is increased in a reaction with more gas molecules on the reactant side, what happens?
A) Shift to product side
B) Shift to reactant side
C) No change
D) Catalyst needed
E) Temperature drops
19. Which factor does NOT affect the rate of reaction but can affect equilibrium position?
A) Temperature
B) Concentration
C) Pressure
D) Catalyst
E) Volume
20. For a reaction with ΔH < 0, increasing temperature will:
A) Favor reactants
B) Favor products
C) No shift
D) Form gas
E) Increase K_eq
- Questions on Equilibrium Constant (K_eq) and Calculations
- Questions on Nonreversible Reactions
- Questions on Le Châtelier's Principle
Answer Key with Explanations
1. C – Adding reactants shifts equilibrium toward products.
2. A – Adding product makes the system shift backward to reduce excess.
3. B – More pressure shifts toward fewer gas moles (right in this case).
4. B – Exothermic reactions shift left with increased temperature.
5. C – Removing product shifts equilibrium right to replace it.
6. C – Inert gases at constant volume do not affect equilibrium.
7. A – Pressure drop shifts equilibrium to the side with more gas moles (left).
8. D – Only temperature affects K_eq.
9. D – Catalysts do not affect equilibrium position.
10. C – Equal moles of gas = no shift due to pressure change.
11. C – Adding heat to an endothermic reaction shifts equilibrium right.
12. B – Removing reactants shifts equilibrium left.
13. B – Lowering temperature favors exothermic direction (right).
14. C – Equal concentration increase = no net shift.
15. A – Increasing volume lowers pressure, like decreasing pressure.
16. B – Solids do not affect equilibrium via pressure changes.
17. C – Decreasing temperature in endothermic reaction shifts left.
18. A – Higher pressure favors side with fewer moles, i.e., product side.
19. D – Catalysts affect rate, not equilibrium position.
20. A – For exothermic reactions (ΔH < 0), increased temperature favors reactants.
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