The reaction 2H2 + O2 → 2H2O is classified as a synthesis reaction.
In a synthesis reaction, two or more reactants combine to form a single product. In this example, hydrogen (H2) and oxygen (O2) are combining to produce water (H2O). This type of reaction is fundamental in chemistry as it demonstrates how simpler substances can create more complex ones.
Additionally, this reaction is also exothermic, meaning it releases energy in the form of heat. This is why hydrogen combustion is often used as a fuel source, as it produces water and releases energy efficiently.