L23S10_Thermochem%2C%20Enthalpy%2003-15-10

L23S10_Thermochem%2C%20Enthalpy%2003-15-10 - Chem 1A L23:

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Unformatted text preview: Chem 1A L23: "Thermochemistry, Enthalpy" Lab 7: Solubility and Spontaneity •Goal: Determine the solubility product, Ksp, for Borax. Create a Van’t Hoff plot to determine ΔHº, Δ Sº, and Δ Gº •Tools and Skills: Titrations © 2004 M. Kubinec, A. Pines L23-1 First Law of Thermodynamics w:work + System Work for Gases Pext = F/A (you can’t win) ( you ΔE = q + w Δhh- Summary w = - F Δh = - Pext ΔV 3 E = 2 nRT Expansion Compression 3 Conservation of E E is a state function - + q:heat ΔEuniv = ΔEsys + ΔEsurr = 0 L22-4 © A.Pines, M.Kubinec,UCB ΔV > O w<O ΔV < O w>O L29-6 Surroundings © A.Pines, M.Kubinec,UCB Isothermal Expansion/Compression Pext = F/A Adiabatic Expansion/Compression Pext = F/A Const T : ΔE = ΔH = 0 Δhh- q = 0 : ΔE = w ΔhhExpansion w<O ΔE < O © A.Pines, M.Kubinec,UCB q + ww 0 =- = Expansion wq+ Compression w+ qL22-12 Compression w>O ΔE > O © A.Pines, M.Kubinec,UCB © 2004 M. Kubinec, A. Pines L23-2 L22-14 ChemQuiz© 22.4 A stretched rubber band is suddenly released. released. What happens to to the temperature of temperature the the rubber band ? A) Increases © 2004 M. Kubinec, A. Pines B) Same C) Decreases L23-3 © 2004 M. Kubinec, A. Pines 1 Chem 1A L23: "Thermochemistry, Enthalpy" Summary Standard Enthalpy Change Reactants Σ ΔHfº(R) Products Σ ΔHfº(P) H fº Elements in Standard States ΔHº = Σ ΔHfº(P) – Σ ΔHfº(R) © A.Pines,M.Kubinec,UCB 0 © 2004 M. Kubinec, A. Pines L19-8 L23-5 Thermochemistry aA+bB q = ΔH cC+dD System Endothermic: q > 0 ΔH > 0 E Heat is absorbed System q+ Surroundings © 2004 M. Kubinec, A. Pines L23-6 Thermochemistry aA+bB q = ΔH cC+dD System Endothermic: q > 0 ΔH > 0 E Heat is absorbed Heat is released System Exothermic: q < 0 ΔH < 0 qSurroundings © 2004 M. Kubinec, A. Pines Standard States: ΔHº 1M, 1atm, 298.15 K L23-7 © 2004 M. Kubinec, A. Pines 2 Chem 1A L23: "Thermochemistry, Enthalpy" ChemQuiz© 23.1 ΔHº for the reaction H2O (g) H2O (l) is +44 kJ mol-1. Which is most hazardous at 100ºC ? at 100 A) Water B) Steam C) Water/Steam L23-8 © 2004 M. Kubinec, A. Pines ChemQuiz© 23.2 H C C C OH HH H Propanol HH H ΔHº HCCCH HH H Isopropanol H HOH The isomerization of propanol is endothermic. endothermic. Which burns cooler? cooler? A) Propanol B) Isopropanol C) Same © 2004 M. Kubinec, A. Pines L23-10 Standard Enthalpy of Enthalpy Formation Compounds Hill Elements in Standard States H 0 Compounds © 2004 M. Kubinec, A. Pines L23-12 © 2004 M. Kubinec, A. Pines 3 Chem 1A L23: "Thermochemistry, Enthalpy" Standard Enthalpy Change Reactants Σ ΔHfº(R) Products Σ ΔHfº(P) H Elements in Standard States ΔHº = Σ ΔHfº(P) – Σ ΔHfº(R) © 2004 M. Kubinec, A. Pines 0 L23-13 Standard Enthalpies of Formation (kJ mol-1) H2(g) O2(g) C(s) Al(s) Fe(s) N2(g) 0 +218 +249 +473 C(g) CO2(g) H20(l) H20(g) +717 -394 -286 -242 CH3CH2OH (l) -278 -1274 -824 -1676 L23-14 H(g) O(g) N(g) C6H12O6 (s (s) Fe2O3 (s) (s) Al2O3 (s) (s) © 2004 M. Kubinec, A. Pines ChemQuiz© 23.3 What is ΔHº (kJ mol-1) for the oxidation of Fe ? Fe (s) + O2 (g) (g) Fe2O3 (s) Fe LO2 A) -575 © 2004 M. Kubinec, A. Pines B) -824 C) -1073 L23-15 © 2004 M. Kubinec, A. Pines 4 Chem 1A L23: "Thermochemistry, Enthalpy" ChemQuiz© 23.4 Which of the following will react with Fe2O3 to produce molten Fe? Fe? A) C (s) B) Fe (s) C) Al (s) © 2004 M. Kubinec, A. Pines L23-17 Lecture Complete © 2004 M. Kubinec, A. Pines L23-19 © 2004 M. Kubinec, A. Pines 5 ...
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