Chem20B_week6 - Covel Tutoring Chem 20B lectures 1 2 Sophia...

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Covel Tutoring Chem 20B- lectures 1 & 2 Sophia Yang – [email protected] Week 6 Topic: Thermochemistry (II) Enthalpies of Reaction: Enthalpy of fusion: Enthalpy of vaporization: Standard state enthalpies: Isothermal Processes: Adiabatic Processes:
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Problem #1: A sample of pure solid naphthalene (C10H8) weighing 0.6410g is burned completely with oxygen to CO 2 (g) and H 2 O(l) in a constant-volume calorimeter at 25°C. The amount of heat evolved is observed to be 25.79 kJ. a) Write and balance the chemical equation for the combustion reaction. b) Calculate the standard change in internal energy ( U°) for the combustion of 1.000mol naphthalene to CO 2 (g) and H 2 O(l). c) Calculate the standard enthalpy change ( H°) for the same reaction as in part b). d) Calculate the standard enthalpy of formation per mole of naphthalene, using data for the standard enthalpies of formation of CO 2 (g) and H 2 O(l) from appendix Problem #2: Suppose 2.0 mol of a monatomic ideal gas (c
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Unformatted text preview: v = 3/2R) is expanded adiabatically and reversibly from a temperature T = 300K, where the volume of the system is 20.0L, to a volume of 60.0L. Calculate the final temperature of the gas, the work done on the gas, and the energy and enthalpy changes. Problem #3: The measured enthalpy change for burning ketene (CH 2 CO) CH 2 CO(g) + 2O 2 (g) 2CO 2 (g) + H 2 O(g) Is ∆ H 1 = -981.1kJ at 25°C. The enthalpy change for burning methane CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(g) Is ∆ H 2 = -802.3 kJ at 25°C. Calculate the enthalpy change at 25°C for the reaction 2CH 4 (g) + 2O 2 (g) CH 2 CO(g) + 3H 2 O(g) Problem #4: The standard enthalpy change of combustion [to CO 2 (g) and H 2 O(l)] at 25°C of the organic liquid cyclohexane, C 6 H 12 (l) is -3923.7 kJ/mol. Determine the ∆ H° f of C 6 H 12 (l)....
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