Question 1: Define an exothermic reaction.

Answer: An exothermic reaction is a chemical reaction that releases energy, usually in the form of heat, to its surroundings.

Question 2: Explain the main difference between an exothermic and an endothermic reaction in terms of energy change.

Answer: In an exothermic reaction, energy is released to the surroundings, while in an endothermic reaction, energy is absorbed from the surroundings.

Question 3: Describe what a reaction profile diagram shows about the energy changes during a reaction.

Answer: A reaction profile diagram shows the energy of the reactants and products, the activation energy needed to start the reaction, and whether the reaction is exothermic or endothermic based on the overall energy change.

Question 1: A reaction releases 150 kJ of energy. If the mass of the reactants involved is 50 grams, what is the energy released per gram? Show your working.

Answer: 3 kJ per gram

Question 2: The activation energy for a certain reaction is 75 kJ/mol. If 2 mol of reactant are involved, what is the total activation energy required? Show your working.

Answer: 150 kJ

Question 1: Identify two variables that need to be controlled in an experiment investigating the temperature change during a reaction.

Answer: Concentration of reactants and temperature

Question 2: List two safety precautions that should be taken when handling chemicals in an energy change experiment.

Answer: Wearing safety goggles and working in a well-ventilated area

Question 1: A reaction has a reaction profile where the energy of the products is lower than the energy of the reactants. What type of reaction is this? Explain your reasoning.

Answer: It is an exothermic reaction because the products have less energy than the reactants, indicating energy has been released.

Question 2: A certain energy profile shows a high activation energy but a small difference in energy between reactants and products. What does this suggest about the reaction's speed and energy change?

Answer: It suggests the reaction has a high activation energy, so it proceeds slowly, but the small energy difference indicates it is neither strongly exothermic nor endothermic.

Question 1: Explain why reaction profiles are useful for understanding energy changes during chemical reactions. (6 marks)

Answer: Reaction profiles visually represent the energy changes throughout a reaction, showing activation energy, whether the reaction is exothermic or endothermic, and the energy difference between reactants and products. This helps in predicting reaction behaviour, speed, and energy requirements, making it a valuable tool for chemists in designing and controlling reactions.

Question 1: Explain how reaction profiles can assist in designing safer and more efficient chemical processes in the industry.

Answer: Reaction profiles help identify the activation energy and energy released or absorbed, enabling industries to optimise conditions for safety, energy efficiency, and yield, and to minimise risks of unexpected reactions or explosions.