Unit 8: Chemical Equilibrium

21. In which direction does the equilibrium shift when a reactant is removed from a system at equilibrium?

a) To the right
b) To the left
c) No change
d) Depends on the concentration of products
Answer: b) To the left

22. Which of the following conditions favors the formation of products in an endothermic reaction at equilibrium?

a) Increasing temperature
b) Decreasing temperature
c) Increasing pressure
d) Adding a catalyst
Answer: a) Increasing temperature

23. What is the equilibrium constant expression (KpK_pKp​) for the reaction 2SO2(g)+O2(g)⇌2SO3(g)2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)2SO2​(g)+O2​(g)⇌2SO3​(g)?

a) [SO3]2/[SO2]2[O2][SO_3]^2/[SO_2]^2[O_2][SO3​]2/[SO2​]2[O2​]
b) [SO2]2[O2]/[SO3]2[SO_2]^2[O_2]/[SO_3]^2[SO2​]2[O2​]/[SO3​]2
c) [SO3]/[SO2][O2]2[SO_3]/[SO_2][O_2]^2[SO3​]/[SO2​][O2​]2
d) [SO3]2/[SO2]2[O2]2[SO_3]^2/[SO_2]^2[O_2]^2[SO3​]2/[SO2​]2[O2​]2
Answer: a) [SO3]2/[SO2]2[O2][SO_3]^2/[SO_2]^2[O_2][SO3​]2/[SO2​]2[O2​]

24. In the reaction 2NO2(g)⇌N2O4(g)2NO_2(g) \rightleftharpoons N_2O_4(g)2NO2​(g)⇌N2​O4​(g), what happens when the volume is decreased?

a) Equilibrium shifts to the right
b) Equilibrium shifts to the left
c) No effect on equilibrium position
d) Reaction rate decreases
Answer: a) Equilibrium shifts to the right

25. What is the relationship between KcK_cKc​ and KpK_pKp​ for a gaseous reaction?

a) Kp=Kc(RT)ΔnK_p = K_c(RT)^{\Delta n}Kp​=Kc​(RT)Δn
b) Kc=Kp(RT)ΔnK_c = K_p(RT)^{\Delta n}Kc​=Kp​(RT)Δn
c) Kc=Kp/RTK_c = K_p/RTKc​=Kp​/RT
d) Kp=Kc/RTK_p = K_c/RTKp​=Kc​/RT
Answer: a) Kp=Kc(RT)ΔnK_p = K_c(RT)^{\Delta n}Kp​=Kc​(RT)Δn

26. Which of the following reactions is an example of a heterogeneous equilibrium?

a) H2(g)+I2(g)⇌2HI(g)H_2(g) + I_2(g) \rightleftharpoons 2HI(g)H2​(g)+I2​(g)⇌2HI(g)
b) CaCO3(s)⇌CaO(s)+CO2(g)CaCO_3(s) \rightleftharpoons CaO(s) + CO_2(g)CaCO3​(s)⇌CaO(s)+CO2​(g)
c) N2(g)+3H2(g)⇌2NH3(g)N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)N2​(g)+3H2​(g)⇌2NH3​(g)
d) 2NO(g)+O2(g)⇌2NO2(g)2NO(g) + O_2(g) \rightleftharpoons 2NO_2(g)2NO(g)+O2​(g)⇌2NO2​(g)
Answer: b) CaCO3(s)⇌CaO(s)+CO2(g)CaCO_3(s) \rightleftharpoons CaO(s) + CO_2(g)CaCO3​(s)⇌CaO(s)+CO2​(g)

27. Which of the following statements is true regarding equilibrium in a closed system?

a) The forward reaction stops completely
b) The reverse reaction stops completely
c) Both forward and reverse reactions continue at the same rate
d) The reaction reaches a static state
Answer: c) Both forward and reverse reactions continue at the same rate

28. Which of the following will NOT change the position of equilibrium in a chemical reaction?

a) Temperature change
b) Concentration change
c) Catalyst addition
d) Pressure change
Answer: c) Catalyst addition

29. If Kc<1K_c < 1Kc​<1, what does this indicate about the reaction at equilibrium?

a) Products are favored
b) Reactants are favored
c) Equilibrium lies far to the right
d) The reaction is at completion
Answer: b) Reactants are favored

30. What is the effect of decreasing temperature on an exothermic reaction at equilibrium?

a) Equilibrium shifts to the right
b) Equilibrium shifts to the left
c) No effect on equilibrium position
d) Decreases the equilibrium constant
Answer: a) Equilibrium shifts to the right