Final answer:
The reaction 2 H₂ + O₂ → 2 H₂O is a redox reaction because oxygen is reduced (its oxidation number decreases from 0 to -2) and hydrogen is oxidized (its oxidation number increases from 0 to +1). This type of reaction is also known as a synthesis reaction, involving a reductant (hydrogen) and an oxidant (oxygen).
Step-by-step explanation:
To determine whether the reaction 2 H₂(g) + O₂(g) → 2 H₂O(g) is a redox reaction, we need to examine the changes in oxidation numbers for each element throughout the reaction.
Oxygen (O₂) starts with an oxidation number of 0 because it is in its elemental form. In water (H₂O), the oxygen has an oxidation number of -2. This change means that oxygen is being reduced.
Hydrogen (H₂) begins with an oxidation number of 0 as well, being in its elemental form. In H₂O, each hydrogen atom has an oxidation number of +1. Thus, hydrogen is being oxidized.
Since there is a transfer of electrons implied by the change in oxidation numbers, this reaction is indeed a redox reaction. Specifically, it is a synthesis reaction, where hydrogen is the reductant and oxygen is the oxidant. This type of reaction is a common example of a redox process because it involves the formation of a compound (H₂O) directly from its elements (H₂ and O₂).