Chapter 10. Spontaneity, Entropy and Free Energy

Chapter 10. Spontaneity, Entropy and Free Energy - Chapter...

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Chapter 10: Spontaneity, Entropy and Free Energy VanKoppen First Law of Thermodynamics Energy is conserved. The energy of the universe is constant. E = q + w Energy of the system increases when heat is added to the system (q > 0) and when work is done on the system (w > 0). The First Law accounts for energy changes: How much energy is involved in a process? What is the direction of flow: into or out of the system? What is the final form of energy? Chapter 10: Focuses on why a process occurs in a given direction (the first law does not tell us why). A spontaneous process is a process which occurs without outside intervention. For example, a gas expands to fill an entire container spontaneously. The gas molecules in a container will not all move to one side of the container spontaneously. Why not? A spontaneous process may be fast or slow. Thermodynamics tells us the direction in which a process will occur but says nothing about the speed (rate) of a process. Chemical kinetics (Chapter 15) is concerned with the rate of reaction. Entropy is a measure of randomness or disorder. It is the driving force for all spontaneous processes. Natural Progression: Order ——> Disorder Low Entropy ——> High Entropy Entropy (S) corresponds to the number of arrangements (positions and/or energy levels) that are available to a system in a given state. It is closely related to probability. The more ways a particular state can be achieved, the greater is the likelihood (probability) that state will occur. (Nature spontaneously proceeds towards the states that have the highest probabilities of existing). Generally: S solid < S liquid << S gas Because one mole of gas will occupy a greater volume then one mole of liquid or solid, the number of positions available to the gas molecules is greater and the entropy of a gas is therefore greater. For a
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Chapter 10. Spontaneity, Entropy and Free Energy - Chapter...

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