When phosphine is adsorbed on a molybdenum surface, it
decomposes with the metal as a catalyst for the reaction. The
half-lives of the decomposition as a function of the initial
pressure of phosphine for a constant concentration of catalyst are
as follows: 7.6 min/265 torr; 3.7 min/130 torr; 1.7 min/58 torr.
Determine the order of the reaction.