Gas \(\mathrm{A}_{2}\) reacts with gas \(\mathrm{B}_{2}\) to form gas \(\mathrm{AB}\) at a constant temperature. The bond energy of \(\mathrm{AB}\) is much greater than that of either reactant. What can be said about the sign of \(\Delta H ? \Delta S_{\text {sumr }} ? \Delta S ?\) Explain how potential energy changes for this process. Explain how random kinetic energy changes during the process.

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Entropy reflects the number of ways particles can be arranged, thus representing the system's level of randomness or disorder. ewline ewline Using ewline the concept of entropy, we can predict whether processes are naturally favorable or not. In chemical reactions, when the system goes from a state of lower entropy to higher entropy, the reaction is more spontaneous, with ewline ΔS being positive. In the exercise, the formation of AB from A2 and B2 leads to a decrease in the overall quantity of gas molecules, signifying reduced chaos and thus a negative ewline ΔS for the system. This reduction in system entropy suggests that for the reaction to be spontaneous, other factors, like enthalpy change, must be considered.

Exothermic reactions involve the release of energy, typically as heat, to the surroundings. They are recognized by a noticeable increase in temperature. ewline ewline For an exothermic reaction, the energy needed to break reactant bonds is less than the energy released when product bonds are formed, leading to a negative enthalpy change (ewline ewline ewline ewline ewline ewline ewline ewline ewline ewline ewline ewline ewline ewline ΔH). This type of reaction is common in combustion, where burning something releases heat. ewline The exercise's given reaction, where AB is produced from A2 and B2, is an illustration of an exothermic reaction, manifesting with a negative ewline ΔH and a positive ΔS for the surroundings due to increased heat and entropy.

Random kinetic energy refers to the energy of particles moving unpredictably in all directions within a substance. Temperature is a direct measure of this kinetic energy; when a substance heats up, its particles move faster. ewline ewline For instance, during an exothermic reaction, the system's rise in temperature means an increase in random kinetic energy. The step by step solution illustrates that as the reaction gives off heat, the random kinetic energy within the system and its surroundings rises because of the heat flow. This transition of energy can also be thought of as the movement of thermal energy, which notably correlates with entropy—more thermal energy generally means higher entropy or randomness.