The U.S. Environmental Protection Agency (EPA) sets limits on healthful levels o

Question

The U.S. Environmental Protection Agency (EPA) sets limits on healthful levels of air pollutants. The maximum level that the EPA considers safe for lead air pollution is 1.5 pg / m3. If your lungs were filled with air containing this level of lead, how many lead atoms would be in your lungs? (Assume a total lung volume of 5.50 L.) 10. Naturally occurring cobalt consists of only one isotope,59CO, whose relative atomic mass is 58.9332 amu. A synthetic radioactive isotope of cobalt, 60 Co, has a relative atomic mass of 59.9338 amu and is used in radiation therapy for cancer treatment. A 1.5886 g sample of cobalt has an apparent atomic mass of 58.9901 amu. Find the mass of 60Co in this sample.

Explanation / Answer

Volume of Lungs = 5.50 L

We use the conversion

1 L = 10^-3 m3

Volume of lungs = 5.50 * 10^-3 m3

Level of Lead = 1.5 ug / m3

Mass of Lead = 1.5 ug * 5.50 * 10^-3 = 8.25 * 10^-3 ug

We know 1 ug = 10^-6 g

Mass of Lead = 8.25 * 10^-3 * 10^-6 g = 8.25 * 10^-9 grams

Molar mass of Lead = 207.2 g / mol

Moles of Lead = Mass of Lead in grams / Molar mass of Lead

Moles of Lead = 8.25 * 10^-9 / 207.2 = 0.0398 * 10^-9 = 3.98 * 10^-11 moles

Number of atoms of Lead = Number of moles * 6.023 * 10^23 = 3.98 * 10^-11 * 6.023 *10^23

Number of atoms of Lead = 23.97 *10^12 atoms (Answer)

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