Question

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

Options

• combination of carbon and oxygen to form carbon monoxide.

• combination of nitrogen and oxygen to form nitrogen monoxide.

• combination of glucose and oxygen to form carbon dioxide and water.

• combination of zinc and hydrochloric acid to form zinc chloride and hydrogen.

Answer 1

Combination of nitrogen and oxygen to form nitrogen monoxide.

Explanation:

Most combination reactions are exothermic, but the combination of nitrogen and oxygen requires an exceptionally high amount of energy to break the very strong triple bond present in nitrogen molecules (N₂). Because this process absorbs a large amount of heat from its surroundings to proceed, it is an endothermic reaction. Burning carbon, respiration (breaking down glucose), and a metal reacting with an acid all liberate heat energy, making them exothermic.