Answer:
The correct answer is 1.778 milligrams per liter.
Explanation:
Based on the given information, the concentration of chlorine gas given is 27 pounds or 27*453.59 = 12327.93 grams.
The quantity of water given is 750000 gallons or 750000 * 3.754 = 2815500 L
The concentration of chlorine used up by the microorganism is 2.6 mg/L or 0.0026 gm/L.
Thus, for 2815500 L of water, the amount of chlorine used is,
= 2815500 * 0.0026
= 7320.3 grams
The left quantity of chlorine is 12327.93 - 7320.3 = 5007.63 grams
The concentration of residual chlorine is,
= 5007.63 g/2815500 = 0.00177859 or 1.778 mg/L.
