Questions and answers on how to convert things from one unit or system to another
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Mon Mar 21, 2005 10:35 pm
I'm having trouble converting sulfur dioxide concentrations from ppb to ug/m3. Can anyone help me with this?
Tue Mar 22, 2005 1:12 am
"parts per billon" can only compare like quantities, not mixed quantities like volume and mass. billion = 10^9, so 1 ppb is 1 in 10^9 of the same quantity, for example ug/kg.
You know the mass of the SO2. Now, what is your m^3 a m^3 of. You have to know what it is and what it weighs. A m^3 of water has a mass of about 1000 kg (varies a little with temperature). 1 m^3 of airs has a mass of about 1.3 kg at standard temperature and pressure, and varies (considerably) according to the ideal gas law. People are most commonly concerned with pollution of air and water, but if it is something else, you have to find the density and determine the mass.
Wed Mar 30, 2005 10:42 pm
Ideal Gas Law: PV = nRT
Vcont = nRT/P, where:
R = 8.314 N-m/(mol-K)
T = 278 K
P = 101325 N/m2
Vcont/n = RT/P = 0.022810679
Ca = ppm * MW/(RT/P)
MW (SO2) = 64 g/mol
ppb ppm Ca (ug/m3)
SO2 (worst) 59 0.059 166
SO2 (second worst) 16 0.016 45
SO2 (third worst) 15 0.015 42
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