CeO2 (solid) reacted with pressurized HCl(g) at 475-625 K to yield CeOCl(solid), Cl-2(g), and H2O(g). The solids surface was flooded with HCl(g), and the reaction rate was linear. Normalized gas quotients were calculated for an extent of reaction of 0.212 to yield values within the limits of 0.279 167-0.279 314. Enthalpy changes from second law calculations were -9.43 to -6.60 J mol(-1) of Cl-2, and entropy changes were -10.624 to -10.618 J K-1 mol(-1), CeOCl was hydrolyzed at 1050-1270 K to yield H-2(g) and HCl(g). Data normalized for 1 atm total pressure conformed to the conventional plot of log(gas quotient) vs 1/T. H-2 production rates and enthalpy changes varied with input rate of H2O(g). At 1270 K the mol fraction of H-2 in the output gas was highest at 0.069 with an enthalpy change of 206.20 kJ mol(-1) and an entropy change of 110.64 J K-1 mol(-1). The chemical work of producing H-2 decreased with increasing T and extrapolated to zero at about 1865 K. At this T, two of three H2O(g) molecules would be converted to H-2(g). All of the Delta H requirement would be T Delta S.