Chem 1320 1st Edition Lecture 35Outline of Last Lecture I. Thermochemistry II. General Categories of EnergyIII. Law of Conservation of EnergyIV. Transfer of EnergyV. Internal EnergyVI. Quantitate expression of the first law of thermodynamicsOutline of Current LectureI. Endothermic & ExothermicII. State FunctionIII. EnthalpyIV. Heat CapacityCurrent Lecture I. Endothermic process: heat is transferred from the surroundings and must cool by conservation of energyExothermic process: heat transfer from the system from the surroundings, surrounding heat up*** transfer of energy in the form of heat and work and the sign of energy transfer reflects a gain or loss of energy in the systemII. State function: Δu= q+w, property of a system that depends only on the present conditions, but not on how the system got to those conditionsU= state function, change in u is also a state functionQ & W= not state functions; quantities depend on how change occursLess heat is generalized on a longer pathFor a given Δu, q & w must depend on the path taken Less heat is needed when no work was done to the system Note: when Δu is the heat transfer in a process where the change in volume is always 0These 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.- Many reactions are carried out as constant pressure. III. Enthalpy (heat) of reaction: ΔH= Hproducts - Hreactants measure of heat transferred in a process at constant temperature. Calorimetry- measure of ΔHSystem= reaction, surroundings= water- Energy is conserved- No heat is lost to outside and only the water is effected by the reaction- If the reaction is exothermic, the temp of the water increases- If the reaction is endothermic, the temp of the water decreasesIV. Heat capacity: 1. Specific heat capacity- materials that can be weighed out in arbitrary amounts 2. Molar heat capacity- heat capacity per mole of material3. Heat capacity of an object- (calorimeter) total heat capacity for an objectStandard State: most stable form of gas, liquid, or solid. For one mole the standard rate is 25 degrees Celsius or 298K- Gives us a common reference point for comparing enthalpies of reaction, energies associated with reactions- Scaling a reaction scales the changes in enthalpy - Reversing the reaction changes the sign of
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