Problem Statement
The rate law for the reaction
is found from experiment to be
Suggest a mechanism consistent with the rate law.
Solution
Solution:
Solution
Two A molecules collide and energy is transferred from one A molecule to the other molecule making it highly reactive.
This activated molecule (A*) can do one of two things. It (A*) can collide with another molecule to become deactivated (A).
or (2) the activated molecule, A* can decompose to form B and C
For reactions with active intermediates, the reaction coordinated discussed in Chapter 3 now has trough in it and the active intermediate, A*, sit in this trough
Rate Laws
Relative Rates
Net Rates: Rate of Formation of Product
Need to find an expression for CA* because we cannot easily measure the concentration of A*, use PSSH to solve for CA*.
Solving for CA*
Substituting for CA* in Equation (4) the rate of formation of B is
Relative rates overall
For high concentrations of A, we can neglect k3 with regard to k2CA, i.e.,
and the rate law becomes
Apparent first order.
For low concentrations of A, we can neglect k2CA with regard to k3, i.e.,
and the rate law becomes
Apparent second order
Dividing by k3 and letting 
and k = k1 we have the rate law we were asked to derive
