The kinetics of the gas phase reaction SO3 + NH3 + N2 T H3NSO3 + N2 were studied with a flow reactor
coupled to a chemical ionization mass spectrometer for detection of SO3 and H3NSO3. The rate coefficient
for the association reaction SO3 + NH3 + N2 was measured as a function of temperature (280-340 K) and
pressure (20-80 Torr of N2). Analysis of the SO3 decay and H3NSO3 appearance at higher temperatures
yielded rate coefficients for H3NSO3 decomposition and the enthalpy of the reaction SO3 + NH3 T H3NSO3:
∆H°
298K ) -24 ( 1 kcal mol-1