# First-order reactions - 3 | Chemical Kinetics: Rate Laws

Cyclobutane C4H8 decomposes to ethene C2H4 at 700K.

The reaction is first-order and the rate constant k = 0.0150 min-1.

Calculate the fraction of cyclobutene that will remain after 2.00 hour.

First-order reaction:

$\frac{\left[\mathrm{cyclobutane}\right]}{{\left[\mathrm{cyclobutane}\right]}_{0}}$ = e-kt = e-0.015 x 120 = 0.165