Look at the diagram below. State whether this reaction is exothermic or endothermic. Give a reason for your answer.

Look at the diagram below. Is this reaction exothermic or endothermic? Identify the activation energy on the diagram and explain what it represents.

Study the energy profile diagram (Diagram Q3) carefully. Classify this reaction as exothermic or endothermic. Explain how the diagram shows energy transfer to/from the surroundings.

Examine Diagram Q4. Determine whether this reaction is exothermic or endothermic. State what happens to the temperature of the surroundings during this reaction.

Look at Diagram Q5. A student claims this reaction is neither exothermic nor endothermic. Evaluate this claim using the diagram.

In an endothermic reaction, which has more energy: the reactants or the products?

In an exothermic reaction, compare the energy level of the products to that of the reactants. What does this difference represent?

A reaction has an activation energy of 80 kJ/mol and releases 50 kJ/mol of energy overall. Sketch the shape of the energy profile and identify the energy levels of reactants, transition state (peak), and products.

Define activation energy using the energy profile diagram concept.

The combustion of methane is exothermic. CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l). Explain, in terms of bond breaking and bond making, why this reaction is exothermic.

If energy is released to the surroundings during a chemical reaction, how does the total energy of the chemicals change? What type of reaction is this?

A student dissolves ammonium nitrate in water and notices the test tube feels cold. Explain this observation in terms of energy transfer and classify the reaction type.

A catalyst is added to a reaction. Draw and explain how this changes the energy profile diagram. Does the ΔH value change?

Two reactions are compared: Reaction X has Ea = 20 kJ/mol, and Reaction Y has Ea = 120 kJ/mol. Both reactions have the same negative ΔH. Which reaction is faster at the same temperature, and why?

The thermal decomposition of calcium carbonate is: CaCO₃(s) → CaO(s) + CO₂(g). This reaction only occurs when heated strongly. Using the energy profile diagram concept, explain why constant heating is required.