The equilibrium between sodium hydrogen acetylide and disodium acetylide

Abstract

Attempts to determine the equilibrium pressure of acetylene over the solid phases in the system 2NaHC₂⇌ Na₂C₂+ C₂H₂ were unsuccessful when appreciable dissociation (>5%) of the hydrogen acetylide occurred; this is due to the polymerisation of acetylene, which is catalysed by the hydrogen acetylide. True dissociation pressures (P) are obtainable when dissociation is small (<0·5%). These are given by log₁₀P/mm = 9·942 – 3363/T, and the heat of dissociation is +15·4 kcal/mol. Dissociation rates for the forward reaction have been measured for the temperature range 120–170 °C, and activation energies for the forward and back reactions found to be 30·8 and 15·4 kcal/mol respectively.