Magnitude of K and Extent of Reaction
The use of the size of the equilibrium constant to judge how far a reaction proceeds before equilibrium is reached.
Formula / equation
K ≫ 1: products favoured
Unit
Dimensionless
In depth
A constant above about 10³ means the reaction is effectively complete, one below 10⁻³ means it barely proceeds, and intermediate values mean appreciable amounts of everything are present at equilibrium. The magnitude says nothing whatever about how quickly that state is reached.
Examples in the real world
The combustion of methane has K near 10¹⁴⁰ and goes to completion; N₂ + O₂ ⇌ 2NO has K ≈ 10⁻³⁰ at room temperature.