Final answer:
The entropy of O2(g) at a constant temperature of 300 K is expected to increase when the pressure is reduced from 200 kPa to 100 kPa because the gas expands, allowing more random distribution of the molecules.
Step-by-step explanation:
The student's question deals with the prediction of how the entropy of oxygen gas (O2) changes as it undergoes a process at constant temperature where the pressure decreases from 200 kPa to 100 kPa. In chemistry, entropy is a measure of the disorder or randomness in a system. The entropy often increases as the gas expands because the molecules have more space to occupy and can increase their distribution of arrangements or microstates.
Since the temperature remains constant at 300 K, and the pressure decreases, the volume in which the oxygen gas molecules can freely move increases, leading to higher randomness or disorder in the system. Therefore, we would predict that the entropy (ΔS) of the substance increases in this process. This prediction is informed by the understanding that expanding a gas at constant temperature typically increases the entropy due to the larger volume and more possible microstates for the gas molecules.