In chemistry, a product is a chemical species resulting from a chemical reaction. Reactants transform into products after entering a high energy transition state. The number and type of atoms in the products of a chemical reaction are the same as the number and type of atoms in the reactants. However, the atoms form different chemical bonds with one another, so products have a different chemical identity from reactants and may be a different state of matter.
Identifying Products in Chemical Equations
By convention, products are on the righthand side of a chemical equation. The reaction arrow points toward products.
A + B → C + D
A and B are reactants and C and D are products.
In reversible reactions, arrows point both directions. This means the species on either side of the arrow act as both reactants and products.
A + B ⇌ C + D
Examples of Products in Chemistry
Here are some examples of products in chemistry, their reactants, and their balanced chemical equations:
- Water, H2O, is the product of the reaction between hydrogen and oxygen:
2 H2 + O2 → 2 H2O
- Silver chloride, AgCl (s), is the product of the reaction between the silver cation and chloride anion in aqueous solution:
Ag+ (aq) + Cl– (aq) → AgCl (s)
- Nitrogen gas and hydrogen gas are the reactants forming ammonia as a product:
N2 + 3 H2 → 2 NH3
- The oxidation of propane yields the products carbon dioxide and water:
C3H8 + 5 O2 → 3 CO2 + 4 H2O
Products in Chemical and Physical Changes
The key difference between a chemical change and a physical change is that the reactants differ from the products in a chemical change, but are the same in a physical change. In other words, no chemical reaction occurs in a physical change, although the reactant may change its state of matter.
For example, melting ice into water is an example of a physical change. The following equation represents the process:
H2O(s) → H2O(l)
The chemical formulas of the reactants and products are the same.
How to Predict Products of a Reaction
Predicting the products of a chemical reaction is mostly a matter of recognizing the type of chemical reaction possible between two reactants. For example, if the reactants are a hydrocarbon and oxygen, it’s a safe bet the products are carbon dioxide and water. A single reactant breaks into multiple products via a decomposition reaction. Two elements combine to form a compound in a ratio that fills their valence electron shells.
But, predicting products also depends on conditions. Sometimes reactants form different products depending on conditions. For example, ammonia reacts with chlorine to form either nitrogen trichloride and hydrochloric acid (when chlorine is in excess) or ammonium chloride and nitrogen (when ammonia is in excess).
- NH3 + 3 Cl2 → NCl3 + 3 HCl
- 8 NH3 + 3 Cl2 → N2 +6 NH4Cl
In the end, the accuracy of predictions is largely a matter of experience and understanding reaction kinetics.
- Atkins, Peter W.; Julio de Paula (2006). Physical Chemistry (4th ed.). Weinheim: Wiley-VCH. ISBN 978-3-527-31546-8.
- IUPAC (1997). “Product”. Compendium of Chemical Terminology (the “Gold Book”) (2nd ed.). Blackwell Scientific Publications: Oxford. ISBN 0-9678550-9-8. doi:10.1351/goldbook.P04861
- Wiberg, Egon; Wiberg, Nils; Holleman, Arnold Frederick (2001). Inorganic Chemistry. Academic Press. ISBN 978-0-12-352651-9.