International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

When are reactions more likely to be exothermic in terms of bond formation?

1. When bonds are formed that release more energy

2. When no bonds are broken in the reaction

3. When the reactants are at higher energy

4. When only weak bonds are involved

The correct answer is: When bonds are formed that release more energy

Reactions are more likely to be exothermic when bonds are formed that release more energy compared to the energy required to break the existing bonds in the reactants. This is rooted in the principle of energy conservation during chemical reactions, where the overall energy change of the reaction depends on the balance between the energy absorbed to break bonds and the energy released when new bonds are formed. In an exothermic reaction, the total energy released during bond formation is greater than the energy absorbed in breaking the bonds of the reactants. This results in a net release of heat, which is characteristic of exothermic processes. Therefore, when strong bonds are formed that release a significant amount of energy, the reaction will have a tendency to be exothermic. Other options do not accurately describe the conditions leading to exothermic reactions. Notably, the absence of bonds being broken would not inherently suggest that the reaction is exothermic; instead, it would imply that no energy is consumed at that stage. Additionally, having reactants at a higher energy level typically indicates that energy must be supplied to facilitate the reaction, making it less likely to be exothermic. Weak bonds being involved could lead to less energy release upon formation, thereby diminishing the likelihood of the