A ground water used as a drinking water supply has a $pH$ of $7\mathrm{.}0$ and a concentration of dissolved arsenic, all present as $A{s}^{\text{I}\text{I}\text{I}},$ of $100\frac{g}{L},$ well above the drinking water standard. The first unit in the treatment plant is prechlorination in a flash mixer $-$ essentially a CFSTR$$which has a water residence time of $2$ minutes. If chlorine is added at a dose sufficient to maintain a constant concentration of $1\mathrm{.}5m\frac{g}{L}$ of free chlorine residual what is the estimated concentration of dissolved

$A{s}^{\text{I}\text{I}\text{I}}$ in the outlet from the flash mixer? How does the answer change for water at $pH6$ or $pH8.$