text: The rate for a bimolecular gas-phase reaction, A + B → product, predicted by collision theory is
  where:
  *k is the rate constant in units of (number of molecules)⋅s⋅m.
  * n is the number density of A in the gas in units of m.
  * n is the number density of B in the gas in units of m. E.g. for a gas mixture with gas A concentration 0.1 mol⋅L and B concentration 0.2 mol⋅L, the number of density of A is 0.1×6.02×10÷10 = 6.02×10 m, the number of density of B is 0.2×6.02×10÷10 = 1.2×10 m
  * Z is the collision frequency in units of m⋅s.
  *  is the steric factor.
  * E is the activation energy of the reaction, in units of J⋅mol.
  * T is the temperature in units of K.
  * R is the gas constant in units of J molK.
  The unit of r(T) can be converted to mol⋅L⋅s, after divided by (1000×N), where N is the Avogadro constant.
  For a reaction between A and B, the collision frequency calculated with the hard-sphere model with the unit number of collisions per m per second is:  
  where: 
  * n is the number density of A in the gas in units of m.
  * n is the number density of B in the gas in units of m. E.g. for a gas mixture with gas A concentration 0.1 mol⋅L and B concentration 0.2 mol⋅L, the number of density of A is 0.1×6.02×10÷10 = 6.02×10 m, the number of density of B is 0.2×6.02×10÷10 = 1.2×10 m.
  *σ is the reaction cross section (unit m), the area when two molecules collide with each other, simplified to , where r the radius of A and r the radius of B in unit m.
  * k is the Boltzmann constant unit J⋅K.
  * T is the absolute temperature (unit K).
  * μ is the reduced mass of the reactants A and B,  (unit kg).
  * N is the Avogadro constant.
  * [A] is molar concentration of A in unit mol⋅L.
  * [B] is molar concentration of B in unit mol⋅L.
  * Z can be converted to mole collision per liter per second dividing by 1000N.
  If all the units that are related to dimension are converted to dm, i.e. mol⋅dm for [A] and [B], dm for σ, dm⋅kg⋅s⋅K for the Boltzmann constant, then 
  unit mol⋅dm⋅s.