The elementary liquid$-$phase reaction A $+$ B $-->D$ is being

conducted isothermally in a $100L$ CSTR$.$ An undesired product $U$

is also produced through the elementary reaction $2AU.$ The

inlet concentration of the reactants are $C_{AO}=C_{B0}=0\mathrm{.}50mo\frac{l}{L}.$

a$)$ Initially, the reactor is operated with a feed rate of $10\frac{L}{m}in.$

The outlet concentration of $B$ is measured to be $C_B=0\mathrm{.}30mo\frac{l}{L},$

and the overall selectivity of $D$ to $U$ is found to be $2\mathrm{.}0.$ What is the

value of the rate constant describing the rate of formation of $D$

$(kD)?$

b$)$ If this reaction were to be run $($using the same feed conditions$)$

in a PFR$,$ what would be the instantaneous selectivity at the PFR

inlet, Sou?