Sapling #11 (Week 9/10)

[Jessica Luong 3K]

I was able to figure out the half-life for this problem, but I am not sure which equation and how to solve it for the next two questions.

Dinitrogen pentoxide, N2O5, decomposes by first‑order kinetics with a rate constant of 3.7×10−5 s−1 at 298 K. What is the half‑life, in hours, of N2O5 at 298 K? --> My answer was 5.2 hrs which was correct.

If [N2O5]0=0.0662 mol⋅L−1, what will be the concentration of N2O5 after 3.1 h?
- I don't know how to solve for this one

How much time, in minutes, will elapse before the N2O5 concentration decreases from 0.0662 mol⋅L−1 to 0.0250 mol⋅L−1?
- I did not know how to answer this as well

[Anthony_3C]

For the first one, since t1/2 for first order is ln2/k, just plug in k. Remember to divide the time by 3600 to get hrs.
For the 2nd and 3rd, use the Arrhenius equation and plug in the initial concentration [A0] which is given and also the given time for the 2nd and the given end concentration [A] for the 3rd.