101308 - y Depends on Physical State-y Additivity-Hesss Law...

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Enthalpies of Formation y Enthalpy of formation- the change in enthalpy that accompanies the formation of one mole of a compound. y Rationale- Enthalpy has no absolute value, it is relative to the elements making up the compound. We measure heat of formation from the elements in their standard states at T = 298 K and P = 1.00 atm.
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Standard States y Compound- for a gas it is 1 atm of pressure, for a solution it is exactly 1 M, for a pure substance (liquid or solid) it is a pure liquid or solid y Elements- the form in which it is the most stable at 1 atm and 25 o C
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Enthalpy of Reaction y Definition- the enthalpy change of the reactants forming products y How do we calculate?
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Combustion of Methane
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Thermite Reaction
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Properties of Enthalpy of Reaction y Extensive Property- y Reversibility-
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Unformatted text preview: y Depends on Physical State-y Additivity-Hesss Law N 2 + O 2 2NO N 2 O + (1/2)O 2 190.74 kJ-99.20 kJ H Hesss Law Hesss Law y Determine the enthalpy change for the oxidation of ammonia: { 4 NH 3 (g) + 5 O 2 (g) 4 NO (g) + 6 H 2 O (l) H = ? { From the following data: { N 2 (g) + 3 H 2 (g) 2 NH 3 (g) H = -99.22 kJ { N 2 (g) + O 2 (g) 2 NO (g) H = +180.5 kJ { 2 H 2 (g) + O 2 (g) 2 H 2 O (l) H = -571.6 kJ Hesss Law y Calculate the enthalpy for the reaction: { BrCl (g) Br (g) + Cl (g) H = ? { By using the following data: { Br 2 (l) Br 2 (g) H = 30.91 kJ { Br 2 (g) 2 Br (g) H = 192.9 kJ { Cl 2 (g) 2 Cl (g) H = 243.4 kJ { Br 2 (l) + Cl 2 (g) 2 BrCl (g) H = 29.2 kJ...
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101308 - y Depends on Physical State-y Additivity-Hesss Law...

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