Question 1: Define an exothermic reaction and explain how it is represented on a reaction profile.

Answer: An exothermic reaction releases heat to the surroundings, shown on a reaction profile as a drop in enthalpy from reactants to products.

Question 2: Describe what the activation energy represents in a reaction profile.

Answer: Activation energy is the minimum energy required for reactant particles to collide successfully and form products, represented as the energy barrier peak.

Question 3: Explain why the energy of the products is lower than that of the reactants in an exothermic reaction.

Answer: Because energy is released during the reaction, resulting in products with lower enthalpy than the reactants.

Question 1: A reaction has an activation energy of 80 kJ/mol and an enthalpy change of -50 kJ/mol. Calculate the overall energy barrier that must be overcome for the reaction to proceed.

Answer: 130 kJ/mol

Question 2: If the energy of the reactants is 200 kJ and the energy of the products is 150 kJ, what is the enthalpy change of the reaction? State whether it is exothermic or endothermic.

Answer: -50 kJ; exothermic

Question 1: Describe a safe method to measure the temperature change during an exothermic reaction in a laboratory setting.

Answer: Use a thermometer with a protective casing, perform the reaction in a well-ventilated area, and wear protective equipment such as goggles and gloves.

Question 2: Identify two variables that could affect the accuracy of measuring energy change in a reaction experiment.

Answer: Reaction temperature stability and measurement timing accuracy.

Question 1: A reaction profile shows a peak energy of 150 kJ/mol and an energy of 50 kJ/mol for the reactants, with products at 20 kJ/mol. Calculate the activation energy and the enthalpy change of the reaction.

Answer: Activation energy = 100 kJ/mol; Enthalpy change = -30 kJ/mol

Question 1: Explain how the shape of a reaction profile can indicate whether a reaction is likely to be fast or slow. Include references to activation energy and energy barriers in your answer.

Answer: A reaction profile with a low activation energy and a small energy barrier suggests a fast reaction, as particles require less energy to overcome the barrier. Conversely, a high activation energy indicates a slow reaction, as fewer particles have sufficient energy to react. The height of the energy barrier relative to reactants determines the reaction rate.

Question 1: Describe how understanding reaction profiles can help in designing safer and more efficient industrial chemical processes.

Answer: By analysing energy barriers and enthalpy changes, chemists can optimise reaction conditions to increase efficiency, reduce energy consumption, and prevent hazardous reactions.

Question 2: Give an example of a common household reaction that releases heat and explain how its reaction profile reflects its exothermic nature.

Answer: Combustion of fuels like methane releases heat, with the reaction profile showing a drop in energy from reactants to products, indicating an exothermic process.