The half-life period for the thermal decomposition of phosphine at three different pressures are given below:
`{:("Pressure in mm. Hg",707 ,79 , 3.5 ),("Half-life period in seconds", 84,84,83):}`
Find the order of the reaction.

Explanation

Since the half-life periods are the same irrespective of the initial concentration, i.e., pressures, the reaction is of the first order.