Question

If 500ml of Lanthnum Chloride solution is enough to remove 1ppm PO4 from 1000L of water, what effect would a dosage of 166ml have on a volume of 30L?

Answer 1

That respective dosage would remove 0.01 ppm phosphate anions`PO_4^(2-)`, from 30 L of water.

The are a couple of ways of solving this problem, but the easiest way I can think of is by using two simple conversion factors.

You know that 500 mL of lanthanum (III) chloride will remove 1 ppm from 1000 L of water. The first conversion factor you'll use will determine how much phosphate anions will be removed by 166 mL of lanthanum (III) chloride in 1000 L of water.

`166cancel("mL") * "1 ppm"/(500cancel("mL")) = "0.332 ppm"`

If you were to add 166 mL of lanthanum (III) chloride to 1000 L of water, that's how much phosphate anions you'd remove. Now you need to see how much you'd remove from 30 L of water

`30cancel("L") * "0.332 ppm"/(1000cancel("L")) = "0.00996 ppm"`

Rounded to one sig fig, the answer will be

`color(green)("0.01 ppm")`