Concentrations of aerosol constituents are sometimes expressed as ppb (mole fraction) to enable comparison with gaseous concentrations expressed in ppb. The unit ppb (mole fraction) is evaluated as RT x concentration of aerosol constituent in nanomoles/m^3. Show that for the nitrate ion, NO_3^-, 1 ppb (mole fraction) is equivalent to 2.14 ppb (mass fraction) at T=293K and 1 atm.