Benzene diazonium chloride in aqueous solution decomposes according to the equation ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{N}}_2\mathrm{Cl}\to {\mathrm{C}}_6{\mathrm{H}}_5\mathrm{Cl} + {\mathrm{N}}_2$. Starting with an initial concentration of $10 \mathrm{g} {\mathrm{L}}^{-1}$, the volume of ${\mathrm{N}}_2$ gas obtained at $50 °\mathrm{C}$ at different intervals of time was found to be as under:

t (min):	$6$	$12$	$18$	$24$	$30$	$\infty$
Volume of ${\mathrm{N}}_2$ (ml):	$19.3$	$32.6$	$41.3$	$46.5$	$50.4$	$58.3$

Show that the above reaction follows the first order kinetics. What is the value of the rate constant?