Question

What are some examples of exothermic reactions?

Answer 1

Reactions in which heat energy is released to its surroundings is classified as exothermic, whereas the opposite, in which heat energy is absorbed, is characterized as endothermic.

The quantity that expresses this heat flow is the enthalpy change, `ΔH`.

A negative `ΔH` value denotes exothermic reactions, because the reaction loses energy.

A positive `ΔH` value denotes an endothermic reaction.

Here are some examples

2Mg + O₂ → 2MgO

The reaction of magnesium metal with oxygen produces magnesium oxide with an enthalpy change of -602 kJ per mole of Mg.

The unit of kJ/mol is used to measure heat energy; it means kilojoules per mole.

The decomposition of potassium chlorate to produce potassium chloride and oxygen gas releases 38.25 kJ per mole of KClO₃.

2KClO₃ → 2KCl + 3O₂

Combustion reactions are exothermic.

The combustion one mole of methanol releases 726.5 kJ.

CH₃OH + 1.5O₂ → CO₂ + H₂O