$4-$The homogeneous gas decomposition of phosphine proceeds at $649C$ with the first$-$order rate What size of plug flow reactor operating at $649C$ and $460$kPa can produce $80\%$ conversion of a feed consisting of $40$mol of pure phosphine per hour?

$4P{H}_3(g)P_4(g)+6H_2$

Answer: $0\mathrm{.}148m^3$