. The thermal decomposition of dinitrogen pentoxide in the gas phase to give nitrogen dioxide and oxygen is a first order reaction. If the half life at 55 °C is 410 s, what is the value of the rate constant k? If the initial concentration of dinitrogen pentoxide in an expt at 55 °C was 0.200 M what will be the concentration of dinitrogen pentoxide, nitrogen dioxide and oxygen after 4 half-lives?

Answer 1

Let the initial and final concentrations be Co and Ct.
To find k:
ln(Ct/Co)=-kt
ln(0.5) = -k(410s)
k = ____?

To find the concentration at (4)(410s), use the same equation:
ln(Ct/Co)=-kt
Use the value of k from the first part, and t = 4x410=1640s, then solve for for Ct.