Rate of reaction of hydrogen with liquid caesium: recalculated rates for lithium and for potassium

Abstract

The rate of absorption of H₂ by stirred liquid Cs to form CsH has been measured from 373 to 576 K, with starting pressures of 20 kN m^–2. The reaction obeys first-order kinetics and only becomes complicated by the dissociation pressure of CsH above 542 K. The apparent activation energy of the reaction is 42.4 kJ mol^–1. Previously reported rates for Li and K are recalculated and the rates are seen now to decrease in the order Li > Cs > K > Na, largely due to the activation-energy term in the Arrhenius equation. The fundamental difference in the rates is attributed tentatively to the differing strengths of the M–H (M = Li, Na, K, or Cs) bonds.