A 50.0 g sample of industrial wastewater contains 0.48 mg of mercury. What is the mercury concentration in ppm?

1. Put both masses in the same unit first: 0.48 mg = 0.00048 g. 2. Form the mass ratio: 0.00048 g / 50.0 g = 9.6 x 10^-6. 3. Multiply by 10^6 to convert the ratio into ppm. 4. The concentration is 9.6 ppm. 5. Multiplying the same ratio by 10^9 gives 9600 ppb, which is the matching value in the smaller unit. 6. The value 0.96 ppm comes from leaving the solute in milligrams while the solution is in grams. 7. The value 96 ppm divides by 5.0 g instead of 50.0 g. _Source: OpenStax Chemistry (CC BY 4.0), Ch 3 "Composition of Substances and Solutions", section 3.4 Other Units for Solution Concentrations_