The decomposition reaction, X → products, has rate constant k = 0.00707 mol L−1 s−1 at a particular temperature. How long will it take for the decomposition to be 90% complete, if the initial concentration of X is 1.65 mol L−1 ?

Answer 1

A look at the units will tell you this is a zero order reaction. So
[A] = [A]o - kt
Ao is 1.65 M so A
A is 90% complete so (A) = 1.65*0.1 = ?
You know k; solve for t