What is the concentration of chlorine in the unknown water?

Question

If 1000 liters of water with an unknown chlorine content are combined with 500 liters of water with 75 ppm (parts per million) of chlorine the result is 55 ppm chlorine. What is the concentration of chlorine in the unknown water?

Answer 1

Hi,

let unknown chlorine content be C ppm in 1000 liters. Therefore from mass balance:

1000 x C + 500 x 75 = (1000 + 500) x 55

=> 1000C +375000 = 1500 x 55

=> 1000C + 37500 = 82500

=> 1000C = 82500 - 37500 = 45000

=> 1000C = 45000

=> C = 45000/1000 = 45 ppm

=> C = 45 ppm

Therefore the unknown chlorine content in 1000 liters of water is 45 ppm. Hope to answer you well. Keep smiling. Chao.