Final answer:
In the reaction 2 H2 + O2 ----> 2 H2O, hydrogen (H2) and oxygen (O2) are the reactants, and water (H2O) is the product.
Step-by-step explanation:
In the chemical reaction 2 H2 + O2 ----> 2 H2O, the reactant(s) are hydrogen (H2) and oxygen (O2). The reactants are substances that exist before the chemical reaction takes place and are typically listed on the left-hand side of the equation. In this case, the 2 H2 represents two molecules of hydrogen, and the O2 represents one molecule of oxygen.
The product(s) of this reaction is water (H2O), which is formed as a result of the chemical reaction between the reactants. The products are the new substances formed and are listed on the right-hand side of the chemical equation. In this particular equation, the presence of the coefficient 2 before H2O indicates that there are two molecules of water produced.