Question

As of the writing of this text, EPA standards limit atmospheric ozone levels in urban environments to 84 ppb. How many moles of ozone would there be in the air above Los Angeles County (area about 4000 square miles; consider a height of 100 m above the ground) if ozone was at this concentration?

Answer 1

At low altitudes (above the sea level) decrease in pressure per 100 m= 1.2 kPa

1 atm=101.325 kpa

1kpa=0.009869 atm

1.2 kpa=0.009869 atm*1.2=0.01184 atm

So at 100 m above sea level pressure=1.0-0.01184 =0.998 atm

Converting ozone concentration ppbv to mg/m3 at t=25 deg C and p=1 atm

1ppb=10^-3 ppm

C=ppmv*12.187*MW/273.15+t

Where c=concentration in mg/m3

1/R=12.187

MW=molecular weight of gaseous pollutant

Ppmv=parts per million by volume

T=ambient temperature in degree celcius

Impact of pressure can be calculated by using ideal gas equation pv=nRT

R=pv/nT=p*22.4/1*273==p/12.187

P=1 atm=1013.25 mb

Eqn becomes, C=ppmv*1013.25 *12.187* MW/p*(273.15+t )

P=ambient atmpheric pressure in millibars

In Los Angeles County,p=0.998 atm=0.998*1013.25 mb/atm=1001.25 mb

Mw of o3=48 g/mol

T=25deg C

C=84*10^-3 ppmv*1013.25*12.187*48g/mol/1001.25*298.15=0.167 mg/m3

1mile=1609.34 m

1sq mile=1609.34^2 sq m=2589975.23 sq m

Area=4000 sq miles*2589975.23 sq m/sq mile=10359900942.4 sq m

C=0.167*10^-3 g/48g/mol per m3=0.00348 mol/m3=3.48*10^-3 mol/m3

moles of ozone would there be in the air above Los Angeles County=3.48*10^-3 mol/area=3.48*10^-3 mol/10359900942.4 =3.358*10^-13 moles (answer)

refer

http://aqicn.org/faq/2015-09-06/ozone-aqi-using-concentrations-in-milligrams-or-ppb/