Lecture_Notes_101209a

# Lecture_Notes_101209a - forming the products y How do we...

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Calorimetry y A 275 mL sample of water at 55.2 o C is in a coffee cup calorimeter. What are the final temperatures when each of the following things at 25.0 o C are added to the hot water? s H2O = 4.18 J/ o C*g, d H2O = 1.00 g/mL y A steel ball, 2.20 cm diameter. d = 7.83 g/mL, s = 0.45 J/ o C*g

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A 5 mL sample of water 5 . 2oC 4 7o C 25.0 o 40.1oC 10% 4% 4% 82% 1. 55.2 o C 2. 54.7 o C 3. 25.0 o C 4. 40.1 o C
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 1.0 atm of pressure, for a solution it is exactly 1M, 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.
Enthalpy of Reaction y Definition- the enthalpy change of the reactants

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Unformatted text preview: forming the products. y How do we calculate? Combustion of Methane Thermite Reaction Properties of Enthalpy of Reaction y Extensive Property-y Reversibility-y Depends on Physical State-y Additivity-Hess’s Law N 2 + O 2 2NO N 2 O + (1/2)O 2 190.74 kJ-99.20 kJ H Hess’s Law Hess’s 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) { From the following data: N 2 (g) + 3 H 2 (g) → 2 NH 3 (g) ∆ H = -99.2 kJ N 2 (g) + O 2 (g) → 2 NO (g) ∆ H = +180.5 kJ 2 H 2 (g) + O 2 (g) → 2H 2 O (l) ∆ H = -571.6 kJ Hess’s Law y Calculate the enthalpy for the reaction: { BrCl (g) → Br (g) + Cl (g) { 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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## This note was uploaded on 10/14/2009 for the course CHEM 105ALg at USC.

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Lecture_Notes_101209a - forming the products y How do we...

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