# 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
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.
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
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
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
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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