Second-Order Reaction
A reaction whose rate depends on the square of one concentration or on the product of two concentrations.
Formula / equation
1/[A] = 1/[A]₀ + kt
Unit
L/(mol·s)
In depth
A plot of reciprocal concentration against time is linear, and the half-life doubles with each successive halving of concentration, so second-order reactions have very long tails. Bimolecular elementary steps are inherently second order.
Examples in the real world
2NO₂ → 2NO + O₂ in the gas phase; the SN2 substitution of a haloalkane by hydroxide.