Question

One of the following is an exothermic reaction. This is:

Options

• electrolysis of water.

• conversion of limestone into quicklime.

• process of respiration.

• process of photosynthesis.

Answer 1

Process of respiration.

Explanation:

During respiration, glucose molecules are broken down and oxidised inside body cells to yield carbon dioxide and water. This biochemical pathway liberates a massive amount of metabolic energy stored as ATP to sustain body functions, making it characteristically exothermic. Conversely, splitting water molecules, calcining limestone, and synthesising glucose via photosynthesis all require continuous energy inputs, classifying them as endothermic.