Chemistry_1031_day27_040109_actual

Chemistry_1031_day27_040109_actual - Dr. Jonathan M. Smith...

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Dr. Jonathan M. Smith Wednesday, April 1
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y Overview y Energy: Ch. 6 y “Heat” of formation y Hess’s Law y Δ H rx y Quantum Chemical Description of the Atom: Ch. 7 y Mastering Chemistry, Energy
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Chapter 6 Thermochemistry
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4 q soln = m x C s x Δ T = - q rxn Mg mol H rxn q = Δ the units and sign are correct 0.158 g Mg, 100.0 mL sol’n, T 1 = 25.6 ° C, T 2 = 32.8 ° C, C s = 4.18 J/ ° C, d soln = 1.00 g/mL Δ H rxn ,J/mol Mg Check: Solution: Concept Plan: Relationship s: Given: Find: T C m s soln Δ × × = q q soln q rxn J 10 0 . 3 J 10 0 . 3 C 7.2 18 . 4 g 10 00 . 1 T 3 soln rxn 3 C g J 2 s soln × = = × = ° × × × = Δ × × = •° q q C m q g 10 00 . 1 mL 1 g 1.00 mL 100.0 2 × = × C 2 . 7 C 6 . 5 2 C 32.8 T ° = ° ° = Δ m, C s , Δ T q soln soln rxn - q q = J/mol 10 4.6 - mol 10 94 9 4 . 6 J 10 0 . 3 Mg mol H 5 3 - 3 rxn × = × × = = Δ q mol 10 94 9 4 . 6 g 24.31 mol 1 Mg g 0.158 3 - × = ×
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Tro, Chemistry: A Molecular Approach 5 y when reaction is multiplied by a factor, Δ H rxn is multiplied by that factor y because Δ H rxn is extensive C( s ) + O 2 ( g ) CO 2 ( g ) Δ H = 393.5 kJ 2 C( s ) + 2 O 2 ( g ) 2 CO 2 ( g ) Δ H = 2( 393.5 kJ) = 787.0 kJ y if a reaction is reversed, then the sign of Δ H is reversed CO 2 ( g ) C( s ) + O 2 ( g ) Δ H = +393.5 kJ
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Tro, Chemistry: A Molecular Approach 6 y if a reaction can be expressed as a series of steps, then the Δ H rxn for the overall reaction is the sum of the heats of reaction for each step
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Tro, Chemistry: A Molecular Approach 7 Given the following information: 2 NO( g ) + O 2 ( g ) 2 NO 2 ( g ) Δ H
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This note was uploaded on 05/09/2010 for the course CHEM 1031 taught by Professor Thomas during the Spring '06 term at Temple.

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Chemistry_1031_day27_040109_actual - Dr. Jonathan M. Smith...

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