Chem 112 Exam AID Course Pack

02 x 10 33 j 129 x 10 15 j 154 x 10 9 j 6 what is

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Unformatted text preview: ll they reach the same temperature − This concerns itself with temperature and thermal equilibrium among bodies. First Law of Thermodynamics: − Energy is conserved it can be changed from one form to another, however it can not be created nor destroyed. − ΔU = q + w − ΔU = change in internal energy (J) − q = heat released/absorbed − w = work done on/by the system € € Heat (q): is not a state function and refers to the thermal transfer • If exothermic process heat is departing the system therefore internal energy is decreased (- ΔU ) • If endothermic process heat is deposited into the system therefore the internal energy is € Ethan Newton & Barry Zhang for SOS Winter 2012 27 € € increased (+ ΔU ) Work (w): is the transfer of energy into or out of the system • Work done ON a system transfers energy into the system (+ ΔU ) € • Work done BY the system uses energy to do work on the surroundings (- ΔU ) W = PΔV € Second Law of Thermodynamics: € If a reaction is spontaneous entropy of the universe increases € Calorimetry: Is the measure of heat change. The heat absorbed or released is given by the following equation. q = mcΔT m: mass c: specific heat ΔT : change in temperature Special cases: − Adiabatic: no heat enters of leaves the system (q=0) − Isothermal: constant temperature is maintained ( ΔT =0) Heat: measured in Joules or calories − Endothermic reactions absorb heat energy (+q) € − Exothermic reactions release heat (- q) The second law can be integrated into the zeroth Heat Lost = - (Heat Gained) m1c1 Tf − T1o = m2c 2 Tf − T2 o Enthalpy: €Preformed under constant pressure (1atm). Enthalpy is used to express the heat changes at constant pressure. The change in the enthalpy is equal to the heat absorbed/released. This a state function that depends on the initial and final states but not the path used to get there. Hence ΔH Rxn = H products − H reac tan ts ΔH Rxn = ΔH ° f (products) − ΔH ° f (reactants) − Endothermic: ΔH Rxn is positive ( € € ) ( ) € Ethan Newton & Barry Zhang for SOS Winter 2012 28 − Exothermic: ΔH Rxn is negative − In the standard state the heat of formation is zero (ex: O2) − Additive (Hess’ Law) − If the pressure is not constant then we measure the internal energy in a similar manner €...
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This note was uploaded on 10/02/2012 for the course CHEM 112 taught by Professor Carran during the Winter '08 term at Queens University.

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