Kinetics and thermodynamics of the reaction H+NH/sub 3/arrow-right-leftNH/sub 2/+H/sub 2/ by the flash photolysis--shock tube technique: Determination of the equilibrium constant, the rate constant for the back reaction, and the enthalpy of formation of the amidogen radical

Journal Article · Fri Jan 15 04:00:00 EST 1988 · J. Chem. Phys.; (United States)

OSTI ID:5616040

Sutherland, J W; Michael, J V

Equilibrium constants K/sub 1/ for the reaction H+NH/sub 3/arrow-right-leftNH/sub 2/+H/sub 2/ were measured over the temperature range 900 to 1600 K using a flash photolysis--shock tube apparatus. The experimental values of K/sub 1/ ranged from 1.0 at 900 K to 2.2 at 1620 K with an estimated experimental error of about +- 10%. The value obtained from the third law analysis for the enthalpy of formation of the amidogen radical, ..delta..H/sup 0//sub f//sub 298/ (NH/sub 2/), is 45.3 kcal/mol (..delta..H/sup 0//sub f//sub 0/ = 46.0). The corresponding value for the bond dissociation energy, D/sup 0/(NH/sub 2/--H), is 107 kcal/mol. These values are in good agreement with the data tabulated in the revised JANAF tables (1982), with those derived from new measurements of the photoionization threshold for the amidogen radical, and with those from independent measurements of the rate constants of the forward and back reactions. The Arrhenius rate expression derived for reaction (-1), NH/sub 2/+H/sub 2/..-->..NH/sub 3/+H, is k/sub -//sub 1/(T) = 5.38 x 10/sup -11/ exp(-6492/T) cm/sup 3/ molecule/sup -1/ s/sup -1/ for the temperature range 900--1620 K. The estimated error in k/sub -//sub 1/(T) is about +- 25%.

• Research Organization: Brookhaven National Laboratory, Department of Applied Science, Upton, New York 11973
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5616040
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 88:2; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AMMONIA
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DECOMPOSITION
DISSOCIATION HEAT
ELEMENTS
ENTHALPY
FORMATION HEAT
HIGH TEMPERATURE
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
KINETICS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PHYSICAL PROPERTIES
REACTION HEAT
REACTION KINETICS
SHOCK TUBES
THERMOCHEMICAL PROCESSES
THERMODYNAMIC PROPERTIES
VERY HIGH TEMPERATURE