Molecular Equation Definition (Chemistry)

A molecular equation shows intact molecules, not the ions into which they may dissociate.
A molecular equation shows intact molecules, not the ions into which they may dissociate. Vladimir Nenov / EyeEm / Getty Images

Molecular Equation Definition

A molecular equation is a balanced chemical equation where the ionic compounds are expressed as molecules instead of component ions.

Examples

KNO3(aq) + HCl(aq) → KCl(aq) + HNO3(aq) is an example of a molecular formula.

Molecular Versus Ionic Equation

For a reaction involving ionic compounds, there are three types of reactions which may be written: molecular equations, complete ionic equations, and net ionic equations.

All of these equations have their place in chemistry. A molecular equation is valuable because it shows exactly what substances were used in a reaction. The complete ionic equation shows all the ions in a solution, while the net ionic equation shows only the ions that participate in a reaction to form products.

For example, in the reaction between sodium chloride (NaCl) and silver nitrate (AgNO3), the molecular reaction is:

NaCl(aq) + AgNO3 → NaNO3(aq) + AgCl(s)

The complete ionic equation is:

Na+(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq) → AgCl(s) + Na+(aq) + NO3-(aq)

The net ionic equation is written by cancelling out the species that appear on both sides of the complete ionic equation and thus don't contribute to the reaction. The net ionic equation is:

Ag+(aq) + Cl-(aq) → AgCl(s)

Format
mla apa chicago
Your Citation
Helmenstine, Anne Marie, Ph.D. "Molecular Equation Definition (Chemistry)." ThoughtCo, Dec. 5, 2017, thoughtco.com/definition-of-molecular-equation-605366. Helmenstine, Anne Marie, Ph.D. (2017, December 5). Molecular Equation Definition (Chemistry). Retrieved from https://www.thoughtco.com/definition-of-molecular-equation-605366 Helmenstine, Anne Marie, Ph.D. "Molecular Equation Definition (Chemistry)." ThoughtCo. https://www.thoughtco.com/definition-of-molecular-equation-605366 (accessed January 24, 2018).