## solving for time elapsed

$\frac{d[R]}{dt}=-k[R]^{2}; \frac{1}{[R]}=kt + \frac{1}{[R]_{0}}; t_{\frac{1}{2}}=\frac{1}{k[R]_{0}}$

Jaira_Murphy_2D
Posts: 31
Joined: Fri Apr 06, 2018 3:00 am

### solving for time elapsed

15.35 The half-life for the second-order reaction of a substance A is 50.5 s when [A]0 0.84 molL. Calculate the time needed for the concentration of A to decrease to (a) one-sixteenth; (b) one-fourth; (c) one-fifth of its original value.

Can someone please explain how to solve part (a)?

I'm pretty sure I have to use the half-life equation to find k and then use the integrated equation to find T but my answer is not the same as the textbook.

dgerges 4H
Posts: 65
Joined: Fri Sep 28, 2018 12:24 am

### Re: solving for time elapsed

find k using the half life equation then use integrated rate law equation for a second life reaction. Ainitial should be 1 and Afinal should be 1/16