Concept:An enthalpy profile diagram plots the internal energy of substances against the progress of a reaction. The relative vertical positions of reactants and products indicate the nature of the heat exchange.
Formula:$$ \Delta H = H_{\text{products}} - H_{\text{reactants}} $$
Solution:- In the provided diagram, the energy level of the Reactants is higher than the energy level of the Products (\( E_R > E_P \)).
- To drop to this lower energy state, the system must shed the excess energy to the surroundings in the form of heat.
- Because heat is released (\( \Delta H = -\text{ve} \)), this specifically represents an exothermic reaction.
Why other options are incorrect:If it were an endothermic reaction, the products would sit at a higher energy level than the reactants. Isothermic means no temperature change occurs, which contradicts a standard enthalpy drop.
Quality & Fidelity Assurance:
Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.