CHEMICAL THERMODYNAMICS 1 chem 16 4 slides per page

CHEMICAL THERMODYNAMICS 1 chem 16 4 slides per page

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Unformatted text preview: any function X as: ∆X = Xfinal – Xinitial If X increases then ∆X > 0 If X decreases then ∆X < 0. Energy Profiles Exothermic reactions generate heat. Eproducts < Ereactants Endothermic reactions absorb heat for complete formation into products. Eproducts > Ereactants ENTHALPY, H • The enthalpy, H, is the heat content at constant pressure. – H = qp – Commonly employed energy measure for chemical reactions since most reactions analyzed occur at constant atmospheric pressure. ENTHALPY of REACTIONS, ∆Hrxn ∆Hrxn is the heat of reaction. If ∆Hrxn < 0 the reaction is exothermic. If ∆Hrxn > 0 the reaction is endothermic. ∆Hrxn = Hproducts - Hreactants ∆Hrxn = Hsubstances produced - Hsubstances consumed ∆Hrxn = Hfinal state – Hinitial state 4 1/7/2014 Thermochemical Equations and Enthalpy of Reactions C5 H12( l ) + 8 O 2(g) → 5 CO 2(g) + 6 H 2 O ( l ) + 3523 kJ 1 mole 8 moles 5 moles 6 moles • The stoichiometric coefficients in thermochemical equations must be interpreted as numbers of moles of each component. • 1 mol of C5H12 reacts with 8 mol of O2 to produce 5 mol of CO2, 6 mol of H2O, and releasing 3523 kJ of heat per mole of reaction. C5 H12(l ) + 8 O 2(g) → 5 CO2(g) + 6 H 2 O (l ) ∆H o = - 3523 kJ/mol rxn N2(g) + 2O2(g) 2NO2(g) ∆Horxn = 15.6 kcal/mol N2(g) + 2O2(g) + 15.6 kcal 2NO2(g) Standard Molar Enthalpies of Formation, ∆Hfo • Standard molar enthalpy of formation - enthalpy for the reaction in which one mole of a substance is formed from its constituent elements. – ∆Hfo kJ/(mole of substance formed) • The standard molar enthalpy of formation fo...
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This document was uploaded on 03/26/2014.

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