Final answer:
The decomposition of hydrogen peroxide is identified as a gas-evolution reaction because it results in the production of oxygen gas and water.
Step-by-step explanation:
The decomposition of hydrogen peroxide is a gas-evolution reaction. This type of reaction is characterized by the production of a gas as a product. In the case of hydrogen peroxide (H₂O₂), when it decomposes, it produces oxygen gas (O₂) and water (H₂O), which can be represented by the following chemical equation:
2 H₂O₂(l) → 2 H₂O(l) + O₂(g)
This reaction is a classic example of a gas-evolution reaction because it generates a gas as one of its products. Unlike combustion reactions, such as the combustion of methane (CH₄), which produces water and carbon dioxide but does not specifically focus on gas evolution, or other processes like photosynthesis and the rusting of iron, which do not produce gas as a primary product, hydrogen peroxide decomposition is characterized by the release of oxygen gas.