Flame-Photometric Determination of the Standard Enthalpies of Formation of Al(0H)2 and AIO

Abstract

Spectrophotometric studies have been made of gas-phase aluminium-containing species in fuel-rich premixed laminar atmospheric-pressure H2+ N2+ O2 flames to which this metal is added. The principal compound formed by Al under the conditions of this work is Al(OH)2. Standard zero-point enthalpy changes and equilibrium constants are determined for two important reactions: Al + 2H2O ⇌ Al(OH)2+ 2H; ΔH°0=–95 ± 30 kJ mol–1, K= 3.0 exp (4300/T);, Al + OH ⇌ AlO + H; ΔH°0=–172 ± 20 kJ mol–1, K= 0.67 exp (19200/T). The results lead to standard zero-point enthalpies of formation for Al(OH)2(g) and AlO(g) from Al(g), O2(g) and H2(g) of –1005 ± 30 and –349 ± 20 kJ mol–1 respectively.