How many pounds of 7% bleach are needed to dose 5,000,000 gallons of water with a concentration of 2 mg/L?

To determine how many pounds of 7% bleach are needed to achieve a concentration of 2 mg/L in 5,000,000 gallons of water, we first need to convert the target concentration into a total mass of bleach required.

1. Convert gallons to liters: There are approximately 3.78541 liters in a gallon. Therefore:

[

5,000,000 \text{ gallons} \times 3.78541 \text{ L/gallon} \approx 18,927,058 \text{ L}

]

2. Calculate the total amount of bleach in milligrams: Since we want a concentration of 2 mg/L, the total mass of bleach needed can be calculated as follows:

[

18,927,058 \text{ L} \times 2 \text{ mg/L} = 37,854,116 \text{ mg}

]

3. Convert milligrams to pounds: There are 453,592 mg in a pound, so:

[

\frac{37,854,116 \text{ mg}}{453,592 \text{ mg/pound}} \approx 83.