In a synthesis reaction, two or more substances combine to form what?

• A. A mixture of reactants
• B. A gas
• C. A solid solution
• D. A single product compound

Answer: (D)

In a synthesis reaction, two or more substances combine to form a single product. The product is typically a new compound with properties different from the starting materials. For example, hydrogen and oxygen can react to form water, which is one single chemical compound. This is why the emphasis is on ending with one product rather than a mixture. A gas can be produced in some syntheses, but that isn’t the defining outcome. A solid solution or a mixture of reactants describes different scenarios that don’t capture the general idea of synthesis. So the description that best fits is a single product compound.