Multiple Choice
A water sample is found to contain the pollutant chlorobenzene with a concentration of 15 ppb (by mass). What volume of this water contains 5.00 × 10² mg of chlorobenzene? (Assume a density of 1.00 g/mL.)
14. Solutions
Parts per Million (ppm)
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Calculate the concentration in parts per billion of the following aqueous solution:0.91 mg of caffeine in a total volume of 131 mL.
A
0.14 ppb
B
0.0069 ppb
C
140 ppb
D
6900 ppb
Verified step by step guidance1
Understand the concept of parts per billion (ppb). It is a unit of concentration that denotes the number of parts of a substance in a billion parts of the solution. It is often used for very dilute solutions.
Convert the mass of caffeine from milligrams to grams, since 1 mg = 0.001 g. This conversion is necessary because the standard unit for mass in chemistry calculations is grams.
Calculate the mass of caffeine in grams: \(0.91 \text{ mg} \times 0.001 \text{ g/mg} = 0.00091 \text{ g}\).
Convert the volume of the solution from milliliters to liters, since 1 mL = 0.001 L. This conversion is necessary because the standard unit for volume in chemistry calculations is liters.
Calculate the concentration in ppb using the formula: \( \text{ppb} = \left( \frac{\text{mass of solute in grams}}{\text{volume of solution in liters}} \right) \times 10^9 \). Substitute the values: \( \text{ppb} = \left( \frac{0.00091 \text{ g}}{0.131 \text{ L}} \right) \times 10^9 \).
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