Question

A pool uses 0.600 M sodium hypochlorite as a chlorine source: NaCl(aq) +H,0 → HOCI (aq) + NaOH(aq) The NaOCI solution flows in at a rate of 1.25 L/min. If the pool has an initial HOCI concentration of 1.00 x 105 M, and the desired HOCI concentration is 1.66 x 10-5 M, how long does it take to reach this desired concentration? The pool has a volume of 23 000 USG, which can be assumed to remain constant. u Nood

Answer 1

Pool volume = 23000 USG = 23000 USG x ( 3.7854 L / 1USG) = 87064 L

Moles of HOCl we have initially = Molarity x volume = 1 x 10^ -5 mol/L x 87064L = 0.87064 mol

Moles of HOCl we need = 1.66 x 10^ -5 mol/L x 87064 L = 1.445 mol

HOCl moles needed to be added = 1.445-0.87064 = 0.5746 = moles of NOCl needed

let time needed be t min , hence volume of NOCl flown = time x rate = t min x 1.25 L/min = 1.25 t Liters

moles of NOCl = M x V = 0.6 mol/L x 1.25t L = 0.75t moles

now equating NOCl moles 0.75 t = 0.5746

t = 0.766 min = 46 seconds