Final answer:
The Carnot engine rejects 2.73 kJ of heat to the reservoir at 300 K.
Step-by-step explanation:
A Carnot engine operates between two heat reservoirs at temperatures of 520 K and 300 K. The engine receives 6.45 kJ of heat energy from the reservoir at 520 K in each cycle. To find the amount of heat rejected to the reservoir at 300 K, we can use the formula for the efficiency of a Carnot engine:
Efficiency (ε) = 1 - (Temperature of the reservoir at 300 K / Temperature of the reservoir at 520 K)
Using the given temperatures, the efficiency of the Carnot engine is 1 - (300 / 520) = 0.423. Since the engine receives 6.45 kJ of heat from the 520 K reservoir, the amount of heat rejected to the 300 K reservoir can be calculated as:
Heat rejected = Efficiency * Heat received = 0.423 * 6.45 kJ = 2.73 kJ