posted by mel .
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 (one million) 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 (M) of each of the following aqueous solutions.
6.7 ppb Hg in H2O
1.0 ppb = 1.0 micrograms/L
6.7 ppb = 6.7 micrograms/L
6.7 micrograms Hg/atomic mass Hg = mols Hg and mols Hg/L = Molarity.