Thermodynamics - Thermodynamics and Equilibrium Equilibrium...

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Thermodynamics and Thermodynamics and Equilibrium Equilibrium
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Contents Contents Energy Changes First Law of Thermodynamics; Enthalpy Second Law of Thermodynamics; Entropy Third Law of Thermodynamics; Standard Entropies Gibbs Free Energy , G, and Spontaneity Standard Free Energies, G 0 , equilibrium constant Free Energy and Maximum Work Free Energy and Equilibrium
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First Law of Thermodynamics First Law of Thermodynamics Total energy is conserved for thermodynamic system Internal energy,E/U, is the sum of kinetic and potentia energies of the particles making up the system. E system = (KE) system + (PE) system E is a State Function E = E final – E initial E is independent of the path. initial initial final final E>0 E<0
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November 1, 2011 CHEM 107, Thermodynamics 4 Internal Energy Internal Energy Kinetic Energy is the energy of motion of molecules Potential Energy is the energy of interactions between molecules including chemical bonding.
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November 1, 2011 CHEM 107, Thermodynamics 5 Heat and Work Heat and Work Changes of internal energy with heat and work E = q + w q + Heat is absorbed by the system q - Heat is released by the system w + Work is done on the system w - Work is done by the system
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November 1, 2011 CHEM 107, Thermodynamics 6 Pressure-Volume Work Pressure-Volume Work work = F d P = F / L 2 work = PdL 2 V=dL 2 work=P V w = - P V atmosphere external
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November 1, 2011 CHEM 107, Thermodynamics 7 Example Example A gas is enclosed in a cylinder with a total mass of 2.20 kg above the piston. The weights are lowered 0.250 m compressing the gas. At the same time, 1.50 J of heat is evolved from the system. What is E? w= Fd = (2.20 kg)(9.80 m/s 2 )(0.250 m) w= 5.39 kg.m 2 /s 2 = 5.39 J E = q + w = -1.50 + 5.39 = 3.89 J
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November 1, 2011 CHEM 107, Thermodynamics 8 Example Example For the combustion of methane in oxygen CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(l) The heat of reaction at 25 0 C and 1.00 atm. is -890.2 kJ. What is the change in volume when 1 mol CH 4 reacts with 2 mol O 2 ? What is w and E for this change? V = V f –V i = 1RT/P- 3RT/P = -2x0.082x298/1 V = - 48.87 L w = - (1.01x10 5 Pa)x(-48.87x10 -3 ) w = 4936 J ⇒∆ E = q + w = -890.2+4.936= -885.2 kJ
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November 1, 2011 CHEM 107, Thermodynamics 9 Heats of Reaction at Constant Heats of Reaction at Constant Volume Volume If the only kind of work is P - V work; E = q + w = q - P V Chemical reaction occuring at constant volume E = q - 0 = q E = q v (Experimental set-up is a bomb calorimeter)
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November 1, 2011 CHEM 107, Thermodynamics 10 Bomb Calorimeter Bomb Calorimeter thermometer Heavy insulation container bomb Electrical ignition water
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November 1, 2011 CHEM 107, Thermodynamics 11 Enthalpy, Heats of Reaction Enthalpy, Heats of Reaction , , P P const const H = E + PV Changes that occur at constant pressure, Enthalpy of Reaction H = E + P V = q - P V + P V = q p
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Thermodynamics - Thermodynamics and Equilibrium Equilibrium...

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