Question

Calculate the molar concentration of the polycyclic aromatic hydrocarbon (PAH), anthracene (178.23 g/mol), that was found in a well water sample at a concentration of 5.61 ppb. Assume the density of the water is 1.00 g/mL.

Answer 1

1 ppm = 1000 ppb

1 ppb = 1/1000 ppm

5.61 ppb = (1/1000)*5.61 ppm

5.61 ppb = 0.00561 ppm

1 ppm = 1 mg/L

0.00561 ppm   = 0.00561 mg/L

molar concentration (M) = ppm*10^-3/Mwt

                      = 0.00561*10^-3/178.23

                      = 3.15*10^-8 M