Question

A cubic meter of air sample was found to contain 65 micrograms of SO2 at 1.0 atm and 25 Celcisus. How many ppd of SO2 is in that air?

25ppb

25ppm

50 ppb

5ppb

Answer 1

ppb (v) is parts per billion by volume

µg/m3 is micrograms of gaseous pollutant per cubic meter of ambient air

The conversion assumes an ambient pressure of 1 atmosphere and a temperature of 25 degrees Celsius.

The general equation is µg/m3 = (ppb)*(12.187)*(M) / (273.15 + °C)

where M is the molecular weight of the gaseous pollutant. An atmospheric pressure of 1 atmosphere is assumed.

a cubic meter = m³

65 micorgrams = 65x10^-6g of SO₂

(65 µg/m³) *(273.15 + °C) / (12.187)*(M) = ppb

ppb = (65 µg/m³)*(298.15) / (12.187)*(64,066 g/mol)

ppb= 24.82 = 25 ppb