Do exothermic reactions increase or decrease entropy?

As a field expert in thermodynamics, I can provide an in-depth explanation of the relationship between exothermic reactions and entropy. Entropy is a measure of the randomness or disorder of a system, and according to the second law of thermodynamics, the total entropy of an isolated system can never decrease over time. It can either remain constant in a reversible process or increase in an irreversible process. The principle is that natural processes tend to move toward a state of greater disorder.
Exothermic reactions are chemical reactions that release energy, usually in the form of heat, to their surroundings. This release of energy is often associated with a decrease in the internal energy of the system. However, the question of whether exothermic reactions increase or decrease entropy is not as straightforward as it might seem.

Firstly, it's important to consider the system and its surroundings when discussing entropy changes. The system refers to the part of the universe under study, while the surroundings are everything else. In an exothermic reaction, the system loses energy, which could suggest a decrease in its entropy due to the release of a more ordered form of energy (chemical energy) into a less ordered form (thermal energy). However, this is only part of the story.

The surroundings, which absorb the heat, experience an increase in entropy. This increase is often greater than the decrease in the system's entropy. The reason for this is that the heat disperses and spreads out in the surroundings, leading to a greater degree of randomness. The total entropy change, which includes both the system and the surroundings, is the sum of the entropy changes of both parts.

The concept of Gibbs free energy (G) is also crucial in this discussion. Gibbs free energy is defined as the maximum reversible work that can be done by a system at a constant temperature and pressure. It is related to the enthalpy (H), temperature (T), and entropy (S) of the system by the equation:
\[ G = H - TS \]

For a spontaneous process at constant temperature and pressure, the change in Gibbs free energy (\( \Delta G \)) must be negative. This means that for an exothermic reaction (\( \Delta H < 0 \)), the entropy change (\( \Delta S \)) must be positive and large enough to overcome the enthalpy change when multiplied by the temperature (T), ensuring that \( \Delta G \) is negative.

In summary, while an exothermic reaction might decrease the entropy of the system due to the conversion of ordered chemical energy to less ordered thermal energy, the overall entropy change of the universe (system + surroundings) is positive. This is because the increase in entropy of the surroundings due to the dispersal of heat is greater than the decrease in the system's entropy. This aligns with the second law of thermodynamics, which states that the total entropy of the universe will always increase over time.

Exothermic reactions don't have increases in entropy of the system, however there is still an OVERALL increase of entropy. AFAIK, even if decreases in an exothermic reaction, the heat released to the surroundings leads to a greater increase in so since: The overall entropy change is still positive.