Chap 5 - Chem 210 Thermochemistry / Chap. 5 Fall 09 UM-SJTU...

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Unformatted text preview: Chem 210 Thermochemistry / Chap. 5 Fall 09 UM-SJTU JI Wang page 1 Chapter 5.1 to 5.7 Chapter 5.1 to 5.7 Thermochemistry Thermochemistry • Nature of Energy • First Law of Thermodynamics • Enthalpy • Enthalpy of Reaction • Calorimetry • Hess’s Law • Enthalpy of Formation Thermochemistry s Thermodynamics Thermodynamics – s Thermo = heat s Dynamics = in motion s Thermochemistry Thermochemistry – s The science of heat transfer through chemical reactions. frequently used terms in thermochemistry s System s well-defined part of the universe s Surroundings s Everything else System + surroundings = universe frequently used terms in thermochemistry s State function s A property of the system s In dependent of the path it took to come to the “current state.” s Function only of the “ current state ” s Examples: temperature, volume, mass , etc. State function System An Examples of Energy as a An Examples of Energy as a State Function State Function Potential energy of hiker 1 and hiker 2 is the same even though they took different paths. final initial : E= E-E Energy Δ frequently used terms in thermochemistry s Closed system s No mass exchange with surroundings. s Such as a sealed reaction vessel surroundings Closed System mass exchange: No No energy exchange: O.K. O.K. frequently used terms in thermochemistry s Isolated system s No mass nor energy exchange with surroundings. s a sealed & insulated reaction vessel surroundings Isolated System No mass exchange No energy exchange Mass & energy Exchange: Energy only Nothing (to a certain extent) Practical Examples Practical Examples Open system Closed system Isolated system frequently used terms in thermochemistry s Energy s Capacity to do WORK or transfer HEAT s Potential Energy (PE) s energy “stored “ s based on static position and force s Between “masses” = gravitational PE s Between“charges” = electrostatic PE s No motion involved Chem 210 Thermochemistry / Chap. 5 Fall 09 UM-SJTU JI Wang page 2 frequently used terms in thermochemistry s Kinetic Energy (KE) s Energy involved in motion s Work (w) s motion of an object against an opposing force s HEAT (q) s random molecular motions s Also called “thermal energy” frequently used terms in thermochemistry s Chemical Energy s A form of Potential Energy (PE) s Mostly based on “ charge ” interactions between / among electrons & nucleus. frequently used terms in thermochemistry s Internal Energy (E) s sum of all the KE and PE of all components of a system s Includes s molecular motions, s chemical E within molecules, and s attractive or repulsive potential E between molecules, s etc. frequently used terms in thermochemistry s Internal Energy (E) s E is a state function s Any changes in E ( ∆ E ) depends only on the initial and final states , and not on how the change occurs ( path )....
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This note was uploaded on 07/30/2011 for the course CHEM 210 taught by Professor Zhang during the Spring '09 term at Shanghai Jiao Tong University.

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Chap 5 - Chem 210 Thermochemistry / Chap. 5 Fall 09 UM-SJTU...

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