F09_230_L9post - CHEM 230 F09 Lecture 9 Chapter 6:...

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CHEM 230 F09 Lecture 9 Chapter 6: Thermodynamics First Law Session ID: 230 Homework 2 due Wed 9/30 at 10pm
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a) C 12 H 22 O 11(s) 12 C (s) + 11 H 2 O (g) + heat b) heat + 2KClO 3(s) 2 KCl (s) + 3O 2(g) c) C (s) + O 2(g) CO 2(g) + heat H 2 SO 4 C Self-Lighting Candle Frozen Beaker Heat + Ba(OH) 2 8H 2 O (s) + 2NH 4 SCN (s) Ba(SCN) 2(s) + 2NH 3(g) + 10 H 2 O (l) http://www.youtube.com/watch?v=vgh76gPSg3M
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Measuring Enthalpy Heat exchange: Temperature change q = mC Δ T q a = -q b Phase change Δ H vap , Δ H fus Measure with calorimeter Reactions Themochemical equations (adding, reversing, stoichiometry) Hess’s Law Heats of formation Bond enthalpy
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Calorimetry Calorimeter: device used to measure the heat absorbed or evolved during a physical or chemical change Constant volume: measures Δ U = q v Constant pressure: measures Δ H = q p = heat of reaction
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Problem A calorimeter with heat capacity equivalent to 0.739 grams of water is used to measure the heat of combustion of 0.303 g of sucrose (C 12 H 22 O 11 MW = 342 g/mol). The temperature increase was found to be 5.00 o C. Calculate the heat that would be released by this reaction C 12 H 22 O 11 (s) + O 2(g) CO 2(g) + H 2 O (g) q rxn = -q Cal = -mC H2O Δ T = -0.739g (4.184 J )(+5 o C) g o C = -15.46 J C s,H2O = 4.184 J/g o C
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Concept Question Is the energy that we just calculated, the energy associated with the combustion reaction as written? A calorimeter with heat capacity equivalent to 0.739 grams of water is used to measure the heat of combustion of 0.303 g of sucrose (C 12 H 22 O 11 MW = 342 g/mol). The temperature increase was found to be 5.00 o C. Calculate the would be released by this reaction C 12 H 22 O 11 (s) + O 2(g) CO 2(g) + H 2 O (g) Δ H rxn = -15.46 J? Yes or No
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Is the energy that we just calculated, the energy associated with the combustion reaction as written? A calorimeter with heat capacity equivalent to 0.739 grams of water is used to measure the heat of combustion of 0.303 g of sucrose (C 12 H 22 O 11 MW = 342 g/mol). The temperature increase was found to be 5.00 o C. Calculate the would be released by this reaction C 12 H 22 O 11 (s) + O 2(g) CO 2(g) + H 2 O (g) Δ H rxn = -15.5 J? Yes
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This note was uploaded on 03/29/2010 for the course CHEMISTRY 230 taught by Professor Gottfried during the Fall '10 term at University of Michigan.

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F09_230_L9post - CHEM 230 F09 Lecture 9 Chapter 6:...

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