Final answer:
Al₂S₃ (s) would have the largest molar entropy due to its molecular complexity and increased disorder.
Step-by-step explanation:
The largest molar entropy will be found in the substance that has the most available microstates or the greatest disorder. This is generally true for substances with larger molecular complexity or those with increased molecular motion and disorder.
Based on the given options, Al₂S₃ (s) would have the largest molar entropy. This is because Al₂S₃ (s) is a compound composed of smaller atoms (Al and S) linked by less rigid bonds, which allows for more disorder and molecular motion within the crystal. In contrast, Al (s) and S (s) are elements with stronger and more rigid atomic bonds, resulting in lower entropies.