The chemical equation describing the burning of hydrogen gas is: 2H2 + O2 ---> 2H2O. Why is this both a synthesis and a combustion reaction?

"A combustion reaction is a reaction in which a substance reacts with oxygen gas, releasing energy in the form of light and heat. Combustion reactions must involve O2 as one reactant. The combustion of hydrogen gas produces water vapor." and "A synthesis reaction occurs when two or more reactants combine to form a single product. ... In a double replacement reaction, two compounds exchange elements. A combustion reaction occurs when a substance reacts quickly with oxygen. Combustion is commonly called burning"

Explanation:

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