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UB CHE 102 - Chemical Thermodynamics

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CHEM 102 1st Edition Lecture 13 Outline of Last Lecture I. Factors That Affect SolubilityII. Precipitation and Separation of IonsIII. Qualitative Analysis for Metallic ElementsOutline of Current LectureI. First Law of ThermodynamicsA. Spontaneous ProcessII. Entropy and Second Law of ThermodynamicsIII. Molecular Interpretation of Entropy ChangesA. Calculations of Entropy ChangesCurrent LectureI. First Law of Thermodynamics- The total energy of the universe is constant, energy is neither created nor destroyed. ΔEsys + ΔEsur = 0 or ΔEsys = q + wSystem- Specific part of the universe which is the focus of the problem. Surroundings- erveything else. Isolated system- isolated from surroundings so neither matter not energy are exchanged. Closed system- one which cannot exchange matter with surroundings but may exchange energy. A. Spontaneous Process- Chemical or physical exchange that occurs in an isolated system without requiring energy from the surroundings, generally exothermic. A process that is spontaneous in one direction is not in the opposite direction, this direction depends on temperature. Ice  water is spontaneous at less than 0 degrees Celsius. -A reversible process is one that can go back and forth between states along the same path. Chemical systems in equilibrium are reversible. In any spontaneous These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.process, the path between reactants and products is irreversible. Thermodynamics gives us the direction of a process, by predicting the speed the process will occur at. II. Entropy and The Second Law of ThermodynamicsEntropy- S, Is a measure of the disorder of a system, it is a state of function with units of J/K-mol. There is a balance between energy and entropy considerations. Spontaneous reactions proceed to lower energy or higher entropy. If S is positive, the randomness increases. Ice has a low entropy, the molecules are very well ordered. Second Law- In any spontaneous process, the entropy of the universe increases. Thechange in entropy of the universe is the sum of the change in entropy of the system and its surroundings. Entropy is not conserved. For a reversible process the change in Entropy of the universe=0. For a spontaneous process it is greater than 0. II. Molecular Interpretation of Entropy- A gas is least orderly, while a solid is the most. Entropy increase as number of gas molecules increases. There are 3 atomic mode of motion: translation, vibration, and rotation, and energy is required for all 3. The more energy stored the higher the entropy. Third Law of Thermodynamics- The entropy of a perfect crystal at 0 K is zero. As we heat a substance from 0, the entropy must increase. The entropy changes drastically at phase changes. A. Calculations of Entropy Changes-     reactantsproducts


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UB CHE 102 - Chemical Thermodynamics

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