Converting grams per kilogram, or g/kg, to grams per cubic meter, or g/m3, inherently poses a challenge because the former relies on a measurement of mass, while the latter involves a measurement of volume. Since both are measurements of concentration, they can both be expressed in parts per million, or ppm. The strategy is to convert g/kg into ppm, then convert the ppm into g/m3. This may be better illustrated by use of an example:
"Express 1g/kg of lead (Pb) in g/m3, assuming a temperature of 25C and pressure of 1 atm."
Instructions
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1
Convert g/kg into ppm. Since 1 mg/kg = 1 ppm, converting g/kg into mg/kg will produce ppm. Do this by multiplying the value by 1,000. For 1 g/kg of lead:
1 g/kg Pb x 1,000 = 1,000 mg/kg Pb = 1,000 ppm Pb
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2
Convert ppm into mg/m3 via this formula: Z mg/m3 = (Y ppm)(molecular weight of substance)/24.45. Since the molecular weight of Pb is 207.2, the formula looks like this:
Z mg/m3 = (1,000 ppm Pb)(207.2)/24.45
Z = 8474.44 mg/m3 Pb
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3
Convert mg/m3 to g/m3, which can be done by dividing the mg/m3 value by 1,000.
8474.44 mg/m3 Pb /1000 = 8.47 g/m3