Which of the following statements best describes an exothermic reaction?

A. Energy is absorbed from the surroundings.

B. The products have higher potential energy than the reactants.

C. Energy is released to the surroundings.

D. The activation energy is zero.

What is the significance of activation energy in a chemical reaction?

A. It is the energy required to break the bonds in the reactants.

B. It is the energy difference between the reactants and products.

C. It is the minimum energy required for a reaction to occur.

D. It is the energy released during the reaction.

Which of the following factors does NOT affect the activation energy of a reaction?

A. Temperature

B. Concentration of reactants

C. Presence of a catalyst

D. Nature of reactants

How does a catalyst affect the activation energy of a reaction?

A. Increases the activation energy

B. Decreases the activation energy

C. Does not change the activation energy

D. Makes the activation energy zero

In a potential energy diagram, how can one distinguish between an exothermic and an endothermic reaction?

A. In exothermic reactions, the products are at a higher energy level than the reactants.

B. In endothermic reactions, the products are at a lower energy level than the reactants.

C. In exothermic reactions, the products are at a lower energy level than the reactants.

D. Both A and B are correct.

a) Explain the difference between exothermic and endothermic reactions in terms of energy changes. [2]

b) Given that a reaction has a positive enthalpy change, classify it as exothermic or endothermic. Justify your answer. [2]

a) Describe the significance of activation energy in a chemical reaction. [2]

b) How does the presence of a catalyst affect the activation energy of a reaction? [2]

a) Using a potential energy diagram, describe the energy changes that occur during an exothermic reaction. [2]

b) In the context of a potential energy diagram, explain the term "energy barrier" for a reaction. [2]

a) Define the term "enthalpy change" in the context of chemical reactions. [2]

b) How is the enthalpy change of a reaction related to the bond energies of the reactants and products? [2]

c) Why might the actual enthalpy change of a reaction in a laboratory differ from the theoretical value? [3]

a) Describe the role of a catalyst in a chemical reaction. [2]

b) How does a catalyst affect the rate of both exothermic and endothermic reactions? [3]

c) Explain why a catalyst does not alter the equilibrium position of a reversible reaction. [2]

Which statement about endothermic reactions is FALSE?

A. They absorb energy from their surroundings.

B. The products have higher potential energy than the reactants.

C. They always occur spontaneously.

D. They often feel cold to touch.

What role does a catalyst play in a chemical reaction?

A. It increases the concentration of reactants.

B. It provides an alternative reaction pathway with a lower activation energy.

C. It changes the nature of reactants.

D. It increases the temperature of the reaction.

In an endothermic reaction, the energy of the products is _______ compared to the reactants.

A. Higher

B. Lower

C. The same

D. Zero

Which of the following will NOT increase the rate of a reaction?

A. Increasing the temperature

B. Adding a catalyst

C. Decreasing the activation energy

D. Decreasing the concentration of reactants

If the activation energy for a reaction is very high, what can be inferred about the reaction?

A. The reaction will be very fast.

B. The reaction will be very slow.

C. The reaction will be exothermic.

D. The reaction will be endothermic.

a) Differentiate between the activation energy of an exothermic reaction and an endothermic reaction using a potential energy diagram. [3]

b) What is the significance of the transition state in a chemical reaction? [2]

c) How do factors such as temperature and concentration affect the activation energy of a reaction? [2]

a) What is Hess's Law, and why is it useful in determining enthalpy changes? [3]

b) Given two reactions with known enthalpy changes, how can you determine the enthalpy change for a third reaction that can be derived from the given reactions? [3]

c) Why is it often more practical to determine enthalpy changes indirectly using Hess's Law rather than directly? [2]

a) Describe the difference between an exothermic and an endothermic reaction in terms of energy changes. [2]

b) Using the concept of potential energy diagrams, explain the term "activation energy". [3]

c) How does the presence of a catalyst affect the activation energy of a reaction? [2]

d) If a reaction has a high activation energy, what can be inferred about its rate at room temperature? [2]

a) What is the significance of the energy barrier in determining whether a reaction is spontaneous or not? [3]

b) List two factors that can influence the activation energy of a reaction. [2]

c) Explain how a catalyst can be specific to a particular reaction. [3]

d) Why might the enthalpy change of a reaction be different when measured in a laboratory compared to its theoretical value? [3]

a) How does the concept of activation energy relate to the stability of reactants and products? [3]

b) Describe the role of a catalyst in both exothermic and endothermic reactions. [3]

c) If a reaction has a negative enthalpy change and a positive entropy change, what can be inferred about its spontaneity at all temperatures? [3]

d) How does the nature of reactants influence the activation energy of a reaction? [2]