The heats of formation of NO₃− and NO₃− association complexes with HNO₃ and HBr

Abstract

Abstract The equilibrium constant for the reaction equation image has been determined between 331 and 480°K using a variable‐temperature flowing afterglow. These data give Δ H °(1) = ‐1.03 ± 0.21 kcal/mol and Δ S °(1) = —4.6 ± 1.0 cal/mol°K. When combined with the known thermochemical values for HBr, Br − , and HNO 3 , this yields Δ H (NO 3 − ) = ‐74.81 ± 0.54 kcal/mol and S (NO 3 − ) = 59.4 cal/mol·°K. In addition Δ H n ‐1, n and Δ S n ‐1, n for the gas‐phase reactions were determined for n = 2 and 3. The implications of these measurements to gas‐phase negative ion chemistry are discussed.