Question

Drinking water plant adds 500g of fluoride to water tank containing 500,000litred of water. What is te concentration of fluoride in ppm

Answer 1

Answer:

Parts per million (ppm) is defined as one-millionth of a gram per gram of the solution for e.g., mg/kg or mg/l.

Mass of fluoride, m = 500 g = 500 * 1000 mg = 500000 mg [∵ 1 g = 1000 mg]

Volume of water, V = 500000 L

We know,

Mass of water = (density of water) * (volume of water)

Since density of water, d = 1 kg/L

∴ Mass of water = 1 kg/L * 500000 L = 500000 kg

Ppm = (weight of solute in mg) / (weight of solution in kg or L)

[here the weight of the solution is equal to the weight of the solvent because the solute is present in very less quantity]

Hence,

The parts per million concentration of fluoride is  

= 500000 mg / 500000 kg

= 1 mg/kg  or 1 ppm