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# Chp9 - Chapter 9 Exercises H S G Problems 9,11,13,15,17,19...

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Chapter 9 Exercises H, S, G Problems 9,11,13,15,17,19 Equilibrium Problems 23,27,29,33,35,39

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Reaction Energetics Thermodynamics Study of energy and its transformations Interested only in E initial and E final Can predict whether reaction is favorable or not Kinetics Process by which reactants form products Rates and mechanism
Squalene Hopene H H H H Reaction Coordinate Energy Different catalyst changes kinetics, not thermodynamics of reaction

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1 st Law of Thermodynamics States that energy is neither created nor destroyed in ANY process Energy is transferred from system to surroundings or vice versa Universe = system + surroundings what you’re studying everything else E universe = 0 E universe = E sys + E sur = 0 E sys = – E sur
Heat (q) and Work (w) Heat (q) and work (w) are the most common ways that energy is exchanged E sys = q + w ( units are J ) + q Heat absorbed by system (endothermic) - q Heat released by system (exothermic) + w Work done ON system - w Work done BY system

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Consider a piston (system) in which n g > 0 Amount of work is P sur x V w = - P sur V relate to moles of gas via ideal gas law w = - n g RT ; R = 8.314 Jmol -1 K -1 Measuring Work (w) P sur n g > 0 V
Enthalpy ( H) Heat of reaction (q) under constant P E = q + w E = H – n g RT When w = 0 ( n g = 0 or V = 0), E = H Fe 2 O 3 + 2 Al Al 2 O 3 + 2 Fe; H = -849 kJ Energy is released, reaction is exothermic Ba(OH) 2 + 2 NH 4 Cl BaCl 2 + 2 NH 3 + 2 H 2 O H = +63.6 kJ Energy is consumed, reaction is endothermic

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R P Energy Energy released by sys (“warms”); H < 0 EXOTHERMIC Weak bonds Strong bonds R P Energy Energy absorbed by sys (“cools”); H > 0 ENDOTHERMIC Weak bonds Strong bonds Energy Diagrams
H° is the standard enthalpy Most stable form of a substance at 1 atm (gas → P of 1 atm; liquid → 1 M at 1 atm) If T is not defined, assume 25 o C Properties of 1 29 n 1) Reverse reaction changes sign of Standard State ( H o )

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2) H° of the reverse reaction is –
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