Chapter6-1

Chapter6-1 - Chapter 6: Thermochemistry 1 Chem 6A Michael...

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Chem 6A Michael J. Sailor, UC San Diego Chapter 6: Thermochemistry 1
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Chem 6A Michael J. Sailor, UC San Diego 2 P Δ V work-a piston expanding System is the piston and everything inside it Surroundings is everything outside the piston
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Chem 6A Michael J. Sailor, UC San Diego 3 Problem: P Δ V work When nitrogen triiodide, NI 3 , detonates, it produces nitrogen gas. When 394.7 g (1 mole) of NI 3 is detonated at 25 °C, 12.2 L of gas is produced. What is the work performed by the gas evolved from the explosion? 2NI 3(s) -> N 2(g) + 3I 2(s) w = P Δ V = - 1.00 Atm x 12.2 L = 12.2 L . Atm = -1239 J (sign is negative because work is done on the surroundings) 12.2 L Atm 101.325 J L Atm
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Chem 6A Michael J. Sailor, UC San Diego Grade Projection Quiz, 1, 2, 3 0 20 40 60 80 100 120 140 160 F D C- C C+ B- B B+ A- A A+ Number of students
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Chem 6A Michael J. Sailor, UC San Diego 5 Stirrer Reaction Vessel Insulation Vent Calorimetry The chemical transformation involved in medical hot packs is the dissolution of calcium chloride in water. The enthalpy of solution, Δ H soln of CaCl 2(s) is -81.3 kJ/ mol. The hot pack contains 140.0 g of water and 30.0 g of CaCl 2(s) . If the pack is initially at room temperature (21.0 °C), what temperature will the mixture become if the reaction goes to completion? Assume the speciFc heat capacity of the aqueous calcium chloride solution is 4.50 J °C -1. g -1 and that the pack is held in a perfectly insulating container.
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Chem 6A Michael J. Sailor, UC San Diego 6 Calorimetry: Solution = 28.7 °C So fnal temperature = 21 + 28.7 = +49.7 °C 81.3 kJ mol CaCl 2 30 g CaCl 2 °C g 1000 J mol 110.98 g CaCl 2 4.50 J 140+30 g solution kJ
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Chem 6A Michael J. Sailor, UC San Diego 7 Problem: Energy and reaction stoichiometry 2 C 8 H 18(l) + 25 O 2(g) 16 CO 2(g) + 18 H 2 O (l) Δ H° = -10,942 kJ The thermochemical equation for the combustion of octane (gasoline) is shown below.
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Chapter6-1 - Chapter 6: Thermochemistry 1 Chem 6A Michael...

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