15_Chapt5 - Thermochemistry Thermochemistry Study of energy changes in chemical processes 2H2 O2 2H2O energy Energy gy kinetic potential First Law

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Thermochemistry Thermochemistry: Study of energy changes in chemical processes Energy 2H 2 + O 2 2H 2 O + energy H for chemical reactions gy kinetic potential irst Law of Calorimetry, Heat Capacity Hess’s Law First Law of Thermodynamics E = q + w Heat of formation H f Standard State H f Enthalpy H Thermochemical Equations Foods and Fuels Mary J. Bojan Chem 110 q 1
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First Law of Thermodynamics Law of conservation of energy gy Energy can be converted from one form to another… …but total energy remains constant. Mary J. Bojan 2 Chem 110
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Energy Kinetic Energy energy of motion Mechanical moving mass (1/2m v 2 ) Electrical moving charge Light photons ound olecules moving uniformly Sound molecules moving uniformly Heat molecules moving randomly otential Energy tored energy Potential Energy stored energy Mechanical mass in a place where a force can act hemical onds Chemical bonds Nuclear binding energy Mary J. Bojan Chem 110 3
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Energy Electronic Energy he potential energy associated with the electrons in The potential energy associated with the electrons in atoms and molecules Chemical energy the Potential Energy associated with bonding H H + H H + O=O + 3 bonds 4 bonds O H H O H H Mary J. Bojan Chem 110 4
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Changes in Energy E = internal energy: total energy (E) associated with a system; the sum of all sources of kinetic & potential energy. the capacity to do work or transfer heat . py E =E final E initial = q + w w = work= action of force through a distance (often P V) ork one to the system (+) work done to the system () q = heat (thermal energy) = energy transferred ue to a difference in temperature due to a difference in temperature. heat added to the system (+) Mary J. Bojan Chem 110 5
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Changes in Energy Energy lost by the SYSTEM is gained by the SURROUNDINGS. The system : what you are interested in atom, molecule, or a atom, molecule, or chemical reaction energy System  Surroundings E = energy Surroundings  System E = + Mary J. Bojan Chem 110 6
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Energy changes Cool the water Which one has more energy? eat the water Heat the water Mary J. Bojan Chem 110 7
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State Function a function whose value does not depend on the athway used to get to the pathway used to get to the present state State Function: only depends on the current state (composition, T,P): does not depend on past history E Mary J. Bojan Chem 110 8
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tate Functions State Functions State functions are written as uppercase letters (E, H, P, V, T, S…) q and w are not state functions but E (= q + w) is a state function Changes in state functions are path-independent Mary J. Bojan Chem 110 9
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This note was uploaded on 01/18/2012 for the course CHEM 110 taught by Professor Hofmann,brucerob during the Fall '08 term at Pennsylvania State University, University Park.

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15_Chapt5 - Thermochemistry Thermochemistry Study of energy changes in chemical processes 2H2 O2 2H2O energy Energy gy kinetic potential First Law

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