A 1400 g sample of stream water contains 12.2 ppm of mercury (Hg). What is the mass of Hg present in the sample?

• A. 12.2 mg
• B. 17.1 mg
• C. 1.22 mg
• D. 0.171 mg

Answer: (B)

Verified step by step guidance

1. Understand that ppm (parts per million) means milligrams of solute per kilogram of solution. So, 12.2 ppm means 12.2 mg of mercury per 1 kg of water.
2. Convert the mass of the water sample from grams to kilograms by dividing by 1000: \(\text{mass in kg} = \frac{1400\, \text{g}}{1000}\).
3. Use the ppm definition to set up a proportion: \(\frac{12.2\, \text{mg Hg}}{1\, \text{kg water}} = \frac{x\, \text{mg Hg}}{\text{mass of sample in kg}}\) where \(x\) is the mass of mercury in the sample.
4. Solve for \(x\) by multiplying the ppm value by the mass of the sample in kilograms: \(x = 12.2 \times \text{mass in kg}\).
5. The result \(x\) will give the mass of mercury in milligrams present in the 1400 g water sample.