Final answer:
The period of the temperature function for the chemical reaction, which oscillates between 25 degrees Celsius and 140 degrees Celsius and returns to its initial temperature over a two-hour cycle, is 2 hours.
Step-by-step explanation:
The question refers to a chemical reaction whose temperature oscillates between a low of 25 degrees Celsius and a high of 140 degrees Celsius. The oscillation of temperature follows a periodic function with respect to time, denoted as y = H(t). Since the temperature reaches its peak in one hour and returns to its starting value in the next hour, the period of the function is the total time for a complete cycle of temperature change, which is 2 hours.