31. At equilibrium, the concentration of products and reactants:

• A) Are necessarily equal
• B) Are at a fixed ratio depending on K
• C) Are always zero
• D) Increase with time
• Answer: B

32. The magnitude of K indicates:

• A) Speed of reaction
• B) Extent of reaction
• C) Initial concentration
• D) Activation energy
• Answer: B

33. The equilibrium constant ( K_p ) is used for:

• A) Gaseous reactions
• B) Liquid reactions
• C) Solid reactions
• D) Ionic reactions
• Answer: A

34. For an exothermic reaction, a decrease in temperature will:

• A) Shift equilibrium right
• B) Shift equilibrium left
• C) No shift
• D) Increase activation energy
• Answer: A

35. A reversible reaction has reached equilibrium when:

• A) Forward reaction stops
• B) Reverse reaction stops
• C) Both rates are equal
• D) Reactants turn into products completely
• Answer: C

36. The law of mass action is used to derive:

• A) Reaction mechanism
• B) Equilibrium constant expression
• C) Rate constant
• D) Activation energy
• Answer: B

37. The value of K changes with:

• A) Catalyst
• B) Temperature
• C) Pressure
• D) Concentration
• Answer: B

38. If a catalyst is added to a system at equilibrium, it will:

• A) Shift equilibrium to products
• B) Shift equilibrium to reactants
• C) Speed up both directions equally
• D) Alter the equilibrium constant
• Answer: C

39. When K >> 1, it indicates:

• A) Reactants dominate
• B) Products dominate
• C) No reaction occurs
• D) Reaction stops
• Answer: B

40. Which does not affect the equilibrium constant?

• A) Temperature
• B) Catalyst
• C) Pressure for gases
• D) Concentration
• Answer: B