The units of parts per million (ppm) and parts per billion (ppb) are commonly used by environmental chemists. In general, 1 ppm means 1 part of solute for every 106 parts of solution. Mathematically, by mass:
ppm = μg solute / g solution = mg solute / kg solution
In the case of very dilute aqueous solutions, a concentration of 1.0 ppm is equal to 1.0 μg of solute per 1.0 mL, which equals 1.0 g solution. Parts per billion is defined in a similar fashion. Calculate the molarity of each of the following aqueous
d. 0.10 ppm DDT (C14H9Cl5) in H2O
We’re being asked to determine the molarity of DDT (C14H9Cl5) in 0.10 ppm DDT in water. Let’s first define ppm and ppb.
• 1 ppm means 1 part of solute for every 106 parts of the solution
in terms of solutions:
• 1 ppb means 1 part of solute for every 109 parts of the solution