In an endothermic reaction, where does the activation energy required to initiate the reaction typically come from?

• A. It is generated internally by the products as they form.
• B. It is provided by the catalyst present in the reaction.
• C. It is released by the reactants during bond formation.
• D. It is supplied by the surroundings in the form of heat.

Answer: (D)

Verified step by step guidance

1. Understand that activation energy is the minimum energy required to start a chemical reaction by allowing reactant molecules to reach the transition state.
2. Recognize that in an endothermic reaction, energy is absorbed from the surroundings because the products have higher energy than the reactants.
3. Know that catalysts lower the activation energy but do not supply the energy themselves; they only provide an alternative pathway.
4. Recall that activation energy is not generated internally by products or released by reactants; instead, it must come from an external source.
5. Conclude that the activation energy in an endothermic reaction is typically supplied by the surroundings, often in the form of heat, to overcome the energy barrier.