Chapter 9 - Questions of the Day Consider diamond. Chapter...

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Questions of the Day Consider diamond. What is its crystal structure? How many carbon atoms are in the unit cell? What is the density of diamond? Chapter 9 Energy and Chemistry Dr. Manuel P. Soriaga Department of Chemistry Thermodynamics is based upon observations of common experience that have been formulated into Laws From these few Laws, all of the remaining Laws of Science are deducible by pure logic Any theory that violates the Laws of Thermodynamics must be discarded Thermodynamics Chemical Thermodynamics Thermodynamics: study of the energy changes associated with physical and chemical processes Chemical thermodynamics: study of energy changes accompanying chemical reactions Thermochemistry: study of heat changes in chemical reactions Observation, measurement, and prediction of energy changes for both physical and chemical processes Use of energy changes to: Predict whether or not a process will occur If process occurs, how to make it more favorable Aspects of Thermodynamics Energy Changes in a Chemical Reaction The reaction: H 2(g) + 1 / 2 O 2(g) H 2 O (g) Releases 242 kJ per mole of water vapor produced
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Energy Capacity to do work Units: Joule (J) = kg m 2 /s 2 = N m = 10 7 ergs Calorie = 4.184 J Potential energy stored energy Kinetic energy “motion” energy Mechanical work: W = F × d For processes that involve gases: P-V work System: Subject(s) involved in the change Surroundings: Everything in the system’s environment Universe: System plus Surroundings Thermodynamic state: Set of conditions that define properties of system Thermodynamic Terms Open System: Mass and energy transfer between system and surroundings Closed System: No mass, only energy, transfer between system and surroundings Isolated System: No mass and no energy transfer between system and surroundings Thermodynamic Terms Change of (Thermodynamic) State Change in Energy Δ E Δ E E fina l E initial = E 2 – E 1 If work or heat added: E final > E initial Δ E > 0 Endergonic If work or heat subtracted: E final < E initial E < 0 Exergonic ± Heat ± Work System at State 1 with Energy E 1 Initial State System at State 2 with Energy E 2 System at State 2 with Energy E 2 Final State H 2(g) + 1 / 2 O 2(g) H 2 O (g) H 2 O (l) Energy Heat absorbed from surroundings (Endothermic) Heat released to
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This note was uploaded on 02/23/2011 for the course CHEM 101 taught by Professor Williamson during the Spring '08 term at Texas A&M.

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Chapter 9 - Questions of the Day Consider diamond. Chapter...

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