Question

5. Write the equation that shows how the rate coefficient depends on temperature.

What is it called?

What is the physical significance of each of the terms in the equation?

What is the rate coefficient for the reaction of OH with methane at 500 K and

250 K

Answer 1

The equation is as follows:

K = A e^-Ea/(RT)

The equation is called as Arrhenius equation which describes the dependence of the rate coeffient K of a chemical reaction on the absolute temperature T.

In this equation the physical significance of the terms is as follows

T is absolute temperature (in kelvins),

A is the pre-exponential factor,

Ea is the activation energy, and

R is the universal gas constant

The reaction of OH with CH4 forms H2O + CH3

OH + CH4 => H2O + CH3

The above example is direct or concerted bimolecular reaction is one in which the reactants A and B proceed to products C and D without the intermediate formation of an AB adduct that has appreciable bonding.

A + B → (AB)≠ → C + D

The rate constants for these reactions are well represented by the Arrhenius expression k = A exp(-E/RT) in particular temperature range.

k = A exp(-E/RT_{(250 - 500)})