We are given:
Maximum concentration of Lead in water = 9 ppb
Mass of Lead in the given solution = 20 grams
Volume of water in the given solution = 250 mL
What is 1 ppb?
1 ppb, short for parts-per-billion. As from its name itself, ppb is used to find how many molecules of solute are present per 1 Billion molecules of the solvent
you can also use it in grams to get the formula:
1 ppb = 1 gram of solute / 1 Billion grams of Solvent
Finding the Ideal ppb concentration:
We are given that the maximum allowed concentration is 9 ppb
which means that we need 9 grams of the solute per 1 Billion grams of Solvent: 9 grams of Solute / 10⁹ grams of Solvent
ppb Concentration of the given solution:
We have 20 grams of Solute in 250 mL of water
Since the density of water is 1 gram/mL
20 grams of Solute / 250 grams of Solvent
As we can see, this fraction is FAR more large that the maximum ppb concentration
This means that the concentration of Lead in the Given solution is higher than the maximum amount and Hence, is unfit to drink