Synthesis Reactions and Examples

Synthesis or Direct Combination Reactions

chemistry synthesis beaker
In a synthesis reaction, simple reactants combine to form a more complex product. Rafe Swan / Getty Images

While there are many types of chemical reactions, they all fall into at least one of four broad categories: synthesis reactions, decomposition reactions, single displacement reactions, or double displacement reactions.

What Is a Synthesis Reaction?

A synthesis reaction or direct combination reaction is a type of chemical reaction in which two or more simple substances combine to form a more complex product.

The reactants may be elements or compounds. The product is always a compound.

General Form of a Synthesis Reaction

The general form of a synthesis reaction is:

A + B → AB

Examples of Synthesis Reactions

These are some examples of synthesis reactions:

  • Synthesis of Water
    2 H2(g) + O2(g) → 2 H2O(g)
  • Synthesis of Carbon Dioxide
    2 CO(g) + O2(g) → 2CO2(g)
  • Synthesis of Ammonia
    3 H2(g) + N2(g) → 2 NH3(g)
  • Synthesis of Aluminum Oxide
    4 Al(s) + 3 O2(g) → 2 Al2O3(s)
  • Synthesis of Iron Sulfide
    8 Fe + S8 → 8 FeS
  • Synthesis of Potassium Chloride
    2 K(s) + Cl2(g) → 2 KCl(s)

Recognizing a Synthesis Reaction

The hallmark of a synthesis reaction is that a more complex product is formed from the reactants. One easy-to-recognize type of synthesis reaction occurs when two or more elements combine to form a compound. The other type of synthesis reaction happens when and element and a compound combine to form a new compound. Basically, to identify this reaction, look for a product which contains all of the reactant atoms.

Be sure to count the number of atoms in both the reactants and products. Sometimes when a chemical equation is written, "extra" information is given that may make it hard to recognize what is going on in a reaction. Counting numbers and types of atoms makes it easier to identify reaction types.

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Helmenstine, Anne Marie, Ph.D. "Synthesis Reactions and Examples." ThoughtCo, Oct. 23, 2017, Helmenstine, Anne Marie, Ph.D. (2017, October 23). Synthesis Reactions and Examples. Retrieved from Helmenstine, Anne Marie, Ph.D. "Synthesis Reactions and Examples." ThoughtCo. (accessed February 17, 2018).