Question

Estimate a steric factor for the gas-phased reaction between O and O₃ given a measured pre-exponencial factor of 8.0 x 10^-12 cm³ molecule^-1 s^-1. State all your assumptions.

( No more information is provided)

Answer 1

The activation energy (E_a) for the oxygen-ozone reaction is 17 kJ/mole O3.

The temperature dependence for the reaction rate constant k,
k = Ae−Ea / RT
where
A is the A-factor or the pre-exponential factor = 8.0 x 10^-12 cm³ molecule^-1 s^-1,
Ea is the activation energy or the threshold energy for reaction = 17 kJ/mole,
R is the gas constant = 8.3144 J K⁻¹ mol⁻¹,
T is the gas temperature 298.15K.

A is related to
molecular cross-section × mean relative collision velocity × steric factor

All of above are my assumptions and are true.

as predicted by collision theory is:

.

where:

• Z is the collision frequency.
• is the steric factor.
• E_a is the activation energy of the reaction.
• T is the temperature.
• R is the gas constant.

The collision frequency is:

where:

• N_A is the Avogadro constant
• σ_AB is the reaction cross section
• k_B is the Boltzmann's constant
• μ_AB is the reduced mass of the reactants.