Many chemical species undergo dimerization reactions. For example, two molecules of butadiene, $\mathrm{C}_4 \mathrm{H}_6$, can combine to form the dimer $\mathrm{C}_8 \mathrm{H}_{12}$. Often such reactions go almost to completion, because the product is more stable than the reactant. Starting with a sample of pure butadiene at time $t=0$, the concentration of butadiene at a later time $t\left(\left[\mathrm{C}_4 \mathrm{H}_6\right](t)\right)$ is given by the expression:
$$
\frac{1}{\left[\mathrm{C}_4 \mathrm{H}_6\right](t)}=\frac{1}{\left[\mathrm{C}_4 \mathrm{H}_6\right](t=0)}+k t
$$
(a) Find an expression for the rate of change of butadiene concentration $\frac{d\left[\mathrm{C}_4 \mathrm{H}_6(t)\right.}{d t}$. The correct expression only contains $\left[\mathrm{C}_4 \mathrm{H}_6\right](t)$ and $k$.
(b) How long does it take for the concentration of butadiene to fall to half of its initial value?