Entropy and Reactions Problem (AP Chemistry)

This is an AP Chemistry-style multiple choice question (MCQ) focusing on entropy (delta S) and reactions. We have to determine which reaction illustrates the least increase in entropy. Entropy measures the amount of disorder in a system. In order to figure this problem out, we need to keep two essential entropy trends in mind: entropy increases as we transition from solid to liquid to gas. Entropy also increases when we create more moles of gas. This problem is particularly applicable to AP Chemistry, but it also is relevant for other exams and curricula, such as MCAT, OAT, DAT, SAT, A-Levels, IGCSE, CBSE, JEE, and NEET.