Reaction Extent

What is this formula?

The extent of reaction is a thermodynamic quantity that measures how far a chemical reaction has progressed relative to its stoichiometric equation.

When to use it

Use this formula when performing reaction engineering calculations, equilibrium analyses, reactor design, or material balance calculations involving chemical reactions.

Example

Reaction:

N2 + 3H2 → 2NH3

Given:

Hydrogen consumed = 1.50 mol

Stoichiometric coefficient of H2 = 3

Formula:

ξ = Δn / ν

Substitution:

ξ = 1.50 / 3

Result:

ξ = 0.50 mol

The reaction has progressed by an extent of 0.50 mol.

Applications

Reaction engineering

Chemical thermodynamics

Equilibrium calculations

Material balances

Reactor design

Note

The extent of reaction is a fundamental stoichiometric variable that allows all species in a reaction to be related through a single parameter. For reactants, Δn is negative because moles are consumed, while for products Δn is positive because moles are formed. In practical calculations, the absolute magnitude is often used when determining reaction progress.