Parts per million (ppm) is a common way to express small concentrations of a solute in water. A sample of tap water that is 25 ppm Cl-Cl - contains 25 grams of Cl-Cl - for every 1,000,000 grams of water. Which units are numerically equal to ppm for dilute aqueous solutions?

A. μg/L

B. cg/L

C. ng/L

D. mg/L

E. g/L

Option D = mg / L

Explanation:

25 ppm of Cl = 25 g / 1000,000 g of water

we will convert g into Kg,

1000,000 / 1000 = 1000 kg

25 ppm of Cl = 25 g / 1000 Kg

we know that 1Kg = 1L that's why 1000 Kg = 1000 L

25 ppm of Cl = 25 g / 1000 L

25 ppm = 0.025 g / L

0.025 g could be written in term of Kg as follow,

0.025 * 1000 = 25 mg

25 ppm = 25 mg / L