Equilibrium concepts chemical equilibrium Kc Kp and Le Chatelier's principle - Question Bank

1. The equilibrium constant Kc for the reaction 2SO3(g) ⇌ 2SO2(g) + O2(g) is 0.04. What is the equilibrium constant for the reaction SO2(g) + 1/2 O2(g) ⇌ SO3(g)?
A) 0.04
B) 1/0.04
C) √0.04
D) 1/√0.04
2. According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in volume, the equilibrium will shift to counteract the change in:
A) Concentration
B) Temperature
C) Pressure
D) Number of moles
3. For the reaction A(g) + B(g) ⇌ C(g) + D(g), if the initial concentrations of A and B are equal, and Kc = 4, what is the equilibrium concentration of C if initial concentrations of C and D are zero?
A) 2/3 M
B) 1/3 M
C) 4/3 M
D) 1 M
4. The value of the equilibrium constant is affected by:
A) Concentration of reactants
B) Concentration of products
C) Presence of a catalyst
D) Temperature
5. Which statement is incorrect regarding equilibrium?
A) Equilibrium is a dynamic state.
B) At equilibrium, macroscopic properties are constant.
C) At equilibrium, the rates of forward and backward reactions are zero.
D) Equilibrium can be approached from either direction.
6. Consider the equilibrium CaCO3(s) ⇌ CaO(s) + CO2(g). If CO2 is removed from the system, the equilibrium will shift:
A) Towards reactants
B) Towards products
C) No change
D) Towards solid formation
7. If Kc = Kp, what can be concluded about the reaction?
A) Δn > 0
B) Δn < 0
C) Δn = 0
D) The reaction involves only solids
8. The equilibrium constant expression for the reaction 2A(g) + B(l) ⇌ 3C(g) is:
A) [C]^3 / ([A]^2 * [B])
B) [C]^3 / [A]^2
C) [A]^2 / [C]^3
D) Kc is undefined
9. For the synthesis of methanol: CO(g) + 2H2(g) ⇌ CH3OH(g) (exothermic). To maximize the yield of methanol, one should:
A) Use high temperature and high pressure
B) Use low temperature and low pressure
C) Use high temperature and low pressure
D) Use low temperature and high pressure
10. Le Chatelier's principle is applicable to:
A) Only chemical equilibria
B) Only physical equilibria
C) Both chemical and physical equilibria
D) Only irreversible reactions
11. If Kc for a reaction is 10^-5, it means that at equilibrium:
A) Products are highly favored
B) Reactants are highly favored
C) Products and reactants are in equal amounts
D) The reaction is very fast
12. For the reaction A(g) ⇌ B(g), if Kc = 0.5 and initial concentration of A is 1 M, what is the equilibrium concentration of B?
A) 0.5 M
B) 0.333 M
C) 0.25 M
D) 0.167 M
13. What is the unit of Kp for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g)?
A) atm
B) atm^-2
C) atm^2
D) No unit
14. What is the unit of Kc for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g)?
A) mol/L
B) (mol/L)^-2
C) (mol/L)^2
D) No unit
15. In a reversible reaction, the equilibrium is reached when:
A) The concentrations of reactants and products are equal.
B) The rate of the forward reaction equals the rate of the backward reaction.
C) The reaction stops completely.
D) The total pressure is at its minimum.
16. Consider the equilibrium 2NO(g) + O2(g) ⇌ 2NO2(g). If the volume of the container is doubled, what will be the effect on the equilibrium?
A) Shift towards products
B) Shift towards reactants
C) No shift
D) Rate of reaction increases
17. For the reaction PCl5(g) ⇌ PCl3(g) + Cl2(g), if the partial pressure of PCl5 is increased by a factor of 2, how will Kp be affected?
A) Doubled
B) Halved
C) Unchanged
D) Quadrupled
18. Which of the following statements is true regarding a system at dynamic equilibrium?
A) The reaction has stopped.
B) The rate of the forward reaction is greater than the rate of the backward reaction.
C) The rate of the forward reaction is less than the rate of the backward reaction.
D) The rate of the forward reaction is equal to the rate of the backward reaction.
19. The equilibrium constant for the reaction 2HI(g) ⇌ H2(g) + I2(g) is K. The equilibrium constant for the reaction HI(g) ⇌ 1/2 H2(g) + 1/2 I2(g) will be:
A) K
B) 1/K
C) √K
D) K^2
20. If Kc = 10 for a reaction A + B ⇌ C + D, and initially [A] = [B] = 1 M, then at equilibrium:
A) [C] = [D] > [A] = [B]
B) [C] = [D] < [A] = [B]
C) [C] = [D] = [A] = [B]
D) [C] = [D] > 1 M
21. For the reaction A(s) + B(g) ⇌ C(g), Kc expression is:
A) [C] / ([A] * [B])
B) [C] / [B]
C) [C]
D) Kc is undefined
22. The equilibrium constant Kc is independent of:
A) Temperature
B) Concentration of reactants
C) Concentration of products
D) Stoichiometry of the reaction
23. In the Haber process for ammonia synthesis, N2(g) + 3H2(g) ⇌ 2NH3(g) + heat, which condition favors high yield of ammonia?
A) High temperature, high pressure
B) Low temperature, low pressure
C) High temperature, low pressure
D) Low temperature, high pressure
24. For the reaction CO(g) + 1/2 O2(g) ⇌ CO2(g), what is Δn?
A) 1
B) -1/2
C) 1/2
D) 0
25. The equilibrium constant for the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g) is Kc. If the reaction is reversed and the reactants and products are swapped, the new equilibrium constant will be:
A) Kc
B) 1/Kc
C) -Kc
D) Kc^2
26. What is the effect of increasing temperature on the equilibrium constant of an endothermic reaction?
A) Increases
B) Decreases
C) Remains unchanged
D) Becomes infinity
27. What is the effect of increasing temperature on the equilibrium constant of an exothermic reaction?
A) Increases
B) Decreases
C) Remains unchanged
D) Becomes zero
28. For the reaction H2(g) + I2(g) ⇌ 2HI(g), Δn = 0. If pressure is increased, the equilibrium:
A) Shifts to the right
B) Shifts to the left
C) Does not shift
D) Is destroyed
29. Which factor does NOT affect the position of equilibrium?
A) Temperature
B) Pressure
C) Concentration
D) Catalyst
30. Consider the reaction A(g) + B(g) ⇌ 2C(g). If the concentration of A is doubled, the equilibrium will shift:
A) Towards reactants
B) Towards products
C) No change
D) To the right
31. For the dissociation of PCl5(g) ⇌ PCl3(g) + Cl2(g), if the volume is decreased, the equilibrium will shift:
A) Towards reactants
B) Towards products
C) No change
D) Towards chlorine formation
32. The addition of a catalyst to a system at equilibrium:
A) Shifts the equilibrium position
B) Increases the equilibrium constant
C) Decreases the equilibrium constant
D) Does not affect the equilibrium position but increases the rate of both forward and backward reactions
33. For an endothermic reaction, decreasing the temperature will cause the equilibrium to shift:
A) Towards the reactants
B) Towards the products
C) No change
D) Towards gaseous products
34. For an exothermic reaction, increasing the temperature will cause the equilibrium to shift:
A) Towards the reactants
B) Towards the products
C) No change
D) Towards solid formation
35. Adding an inert gas to a system at equilibrium at constant pressure will:
A) Shift the equilibrium towards the side with more moles of gas
B) Shift the equilibrium towards the side with fewer moles of gas
C) Not shift the equilibrium
D) Increase the concentration of products
36. Adding an inert gas to a system at equilibrium at constant volume will:
A) Shift the equilibrium
B) Not shift the equilibrium
C) Increase the rate of forward reaction
D) Decrease the rate of backward reaction
37. If the pressure of a gaseous equilibrium system is increased, the equilibrium will shift towards the side with:
A) More moles of gas
B) Fewer moles of gas
C) Equal moles of gas
D) No gas
38. According to Le Chatelier's principle, increasing the concentration of a reactant in a system at equilibrium will cause the equilibrium to shift:
A) Towards the reactants
B) Towards the products
C) No change
D) Towards the solvent
39. Le Chatelier's principle states that if a change of condition is applied to a system in equilibrium, the system will shift in a direction that:
A) Increases the rate of the forward reaction
B) Increases the rate of the backward reaction
C) Relieves the stress
D) Consumes all reactants
40. For a reaction where Δn = 0, what is the relationship between Kp and Kc?
A) Kp > Kc
B) Kp < Kc
C) Kp = Kc
D) Kp = 1/Kc
41. In the expression Kp = Kc(RT)^Δn, Δn represents:
A) Sum of moles of reactants - Sum of moles of products
B) Sum of moles of products - Sum of moles of reactants
C) Sum of moles of all gaseous species
D) Total number of moles in the reaction
42. What is the relationship between Kp and Kc for a gaseous reaction?
A) Kp = Kc(RT)^Δn
B) Kp = Kc(RT)^(-Δn)
C) Kp = Kc + RTΔn
D) Kp = Kc - RTΔn
43. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), the expression for Kp is:
A) (P_NH3)^2 / (P_N2 * (P_H2)^3)
B) (P_N2 * (P_H2)^3) / (P_NH3)^2
C) P_NH3 / (P_N2 * P_H2)
D) (P_N2 * P_H2) / P_NH3
44. The equilibrium constant (Kp) is defined in terms of:
A) Molar concentrations of gases
B) Partial pressures of gases
C) Mole fractions of gases
D) Total pressure of the system
45. If the value of Kc is very small (Kc << 1), it indicates that at equilibrium:
A) Reactants are favored
B) Products are favored
C) Concentrations of reactants and products are equal
D) The reaction is reversible
46. If the value of Kc is very large (Kc >> 1), it indicates that at equilibrium:
A) Reactants are favored
B) Products are favored
C) Concentrations of reactants and products are equal
D) The reaction does not proceed
47. For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), the expression for Kc is:
A) [NH3]^2 / ([N2] * [H2]^3)
B) [N2] * [H2]^3 / [NH3]^2
C) [NH3] / ([N2] * [H2])
D) ([N2] * [H2]) / [NH3]
48. The equilibrium constant (Kc) for a reaction is defined in terms of:
A) Concentrations of reactants only
B) Concentrations of products only
C) Molar concentrations of products raised to stoichiometric coefficients divided by molar concentrations of reactants raised to stoichiometric coefficients
D) Partial pressures of reactants and products
49. Which of the following conditions must be met for a system to be at equilibrium?
A) Forward reaction rate is zero
B) Backward reaction rate is zero
C) Forward reaction rate equals backward reaction rate
D) Concentrations of reactants and products are equal
50. For a reversible reaction, the rate of the forward reaction is equal to the rate of the backward reaction at:
A) The start of the reaction
B) The point of equilibrium
C) The completion of the reaction
D) Any point during the reaction
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