The US Clean Air Act requires the US EPA to set National Ambient Air Quality Sta

Question

The US Clean Air Act requires the US EPA to set National Ambient Air Quality Standards. Ozone is one of the pollutants regulated, and the average concentration (as the annual fourth-highest daily maximum 8-hr concentration, averaged over 3 years) can be no higher than 70 ppb as of Octobcr 1, 2015. What is this concentration in terms of molecules per cubic centimeter at 1 aim and 25degreeC? 2.) The US Safe Drinking Water Act requires the US EPA regulate contaminates in drinking water. Bromate ion is a careinogen that is produced as a by-product of water disinfection, and the bromate ion concentration in finished drinking water can be no higher than 0.010 mg/L as an annual aveerage. Calculate the annual average limit for bromate ion in terms of a.) ppb and b.) molarity. Assume that the density of drinking water is 1 g/mL.

Explanation / Answer

(1) 70 ppm of O3 means 70 moles of O3 is present per 1 million moles of gas or 70 molecules of O3 is present for every 1 million molecules of gas or air.

Molecules of air = 1000000, convert this into volume using the equation PV = nRT

n = 1000000/6.023 x 1023 = 1.66 x 10-18 moles

V = nRT / P = 1.66 x 10-18 x 0.0821 x 298 / 1 = 4.06 x 10-17 L

Convert L to cm3, 1L = 1000cm3

V = 4.06 x 10-14 cm3

It means 70 molecules are present in 4.06 x 10-14 cm3 of air

or 70/4.06 x 10-14 = 17.24 x 1014 molecules/cm3

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.