Energy+Part+1 - system imparts energy to the system so w is...

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Energy and Chemical Reactions – Part 1 Energy - Its Forms and Interconversions System and Surroundings – Energy flow to and from a system ∆E = E final E initial = E products E reactants E final < E initial E < 0 E final > E initial E > 0 Heat and Work – Two Forms of Energy Transfer Heat (thermal energy) q Work (object moved by a force) w E = q + w Define the sign of energy transfer from the system’s perspective. Energy coming into the system is positive. Energy going out from the system is negative. Energy Transfer as Heat Only E = q w = 0 Heat flowing out from the system, q is negative, thus E is negative. Heat flowing into the system, q is positive, thus E is positive. Energy Transfer as Work Only E = w q = 0 1
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Work done by a system – generation of a gas. Energy is lost by the system so w is negative and E is negative. Pressure – Volume work or PV work. Work done on a system – Increase in external pressure on the
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Unformatted text preview: system imparts energy to the system so w is positive and E ∆ is positive. First Law of Thermodynamics – Total energy in the universe is constant. E ∆ universe = E ∆ system + E ∆ surroundings = 0 Energy Units Joule (J) 1J = 1 kg m 2 / s 2 calorie (cal) 1cal = 4.184 J State Functions – depend only on their initial and final states and not the path they took to get there. Example of state functions include E, P and V – q and w may vary but the overall E will ∆ ∆ ∆ ∆ not. Enthalpy – Heats of Reaction Work done by an expanding gas, w = P V negative because − ∆ work is being done on the surroundings by the system. Enthalpy (H) H = E + PV H = E + P V ∆ ∆ ∆ The change in enthalpy equals the heat gained or lost at constant pressure. 2...
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This note was uploaded on 04/13/2008 for the course CHM 2045 taught by Professor Mitchell during the Fall '07 term at University of Florida.

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Energy+Part+1 - system imparts energy to the system so w is...

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