An ______ reaction can continue to occur once it has begun.

• A. Endothermic
• B. Exothermic
• C. Catalytic
• D. Photochemical

Answer: (B)

This question focuses on how energy changes influence whether a reaction can keep going after it starts. An exothermic reaction releases heat as it proceeds. That released heat can raise the temperature of the reacting mixture, which increases the kinetic energy of the molecules and the likelihood of collisions that overcome the activation energy. As long as there are reactants available, this heat feedback can help the reaction continue, much like a flame that sustains itself by the heat of combustion.

Endothermic processes need energy input to proceed, so they won’t inherently keep going once started without a continuous energy supply. Photochemical reactions require light to proceed, so removing light stops them. Catalytic reactions rely on a catalyst to lower the activation energy and speed things up, but the catalyst itself isn’t consumed; it doesn’t by itself guarantee that the reaction will continue after the initial trigger if reactants run out or conditions change.