Question

A cubic meter of air sample was sampled at 1.0 atm and 25 C and was found to contain 2.9 micrograms of NO2. How many ppb of NO2 is in that air?

Answer 1

ppb is parts per billion. ppb is defined as moles of solute divided by total moles of solution times 109 for gaseous solution in dillute form.
we have ideal gas equation 1 pv = nRT from here n = 1 PV RT epiven, pressure pa 1.0 atm volume taken as 1000L. Temperature, 1 = 25°C Gas constant R = 0.082 Latrolkmo - (25+ 273] K 1 = 298k in n = (loatm) x (10001) 0.082 Latmikmol) x(298k) 1000 40.9 mol air = 24436 1. The molar mass of air can be taken as = 28.97 g Imor oms Given, weight of No₂ = 2 Cmolecular) = 2.9x10 The weight of air = noumber of mores of air x molecular weight - 40.9 x 28.97 = 118_4-8739

air The = Ppb of No, in this amount of NO₂ molecular weight of air 2.94100 g NO2 1184.8739 = 2.447 X10-9 = 2.447 ppb NO2

The answer of this problem is 2.447ppb. The method is given below.