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## How can ppm be converted to µg/m |

Vocabulary | |

atm ideal gas law ideal gas law constant kelvin micro moles parts per million |

- 1 gram of SO
_{2}for every million grams of air (parts per million by mass); - 1 mL of SO
_{2}for every million mL of air (parts per million by volume); - 1 gram of SO
_{2}for every million mL of air (parts per million by mass per volume).

**Write "ppm" in terms of cubic meters**. There are a million cubic centimeters in a cubic meter (1 cm^{3}= (10^{-2})^{3}m^{3}= 10^{-6}m^{3}) so one part per million of SO_{2}by volume in air is actually 1 cm^{3}SO_{2}/ 1 m^{3}of air.**Convert cm**. You'll need the density of the gas at the appropriate temperature and pressure. If you don't have the density you can estimate it using the ideal gas law:^{3}of SO_{2}gas to µg SO_{2}PV = nRT

where P is the pressure, V is the volume, n is moles of gas, R is the ideal gas law constant (82.06 atm cm^{3}/mol K) and T is the temperature in kelvins. Since density is mass per unit volume and the mass of the gas is moles of gas times molecular weight M,d = g/V = M (n/V) = MP/RT

For example, at 25°C and 1.00 atm, the density of SO_{2}gas is approximately MP/RT = (64 g/mol)(1 atm)/(82.06 atm cm^{3}/mol K)(298 K) = 0.00262 g/cm^{3}= 2620 µg/cm^{3}.Multiplying parts per million SO

_{2}by volume by the density of SO_{2}in µg/cm^{3}gives you µg/m^{3}.

General Chemistry Online! How can ppm be converted to µg/m

Copyright © 1997-2010 by Fred Senese

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Last Revised 08/17/15.URL: http://antoine.frostburg.edu/chem/senese/101/solutions/faq/converting-ppm-to-micrograms-per-cubic-meter.shtml