# problemset1withanswers - Chem33-1, C-hour Problem Set 1...

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Chem33-1, C-hour Problem Set 1 Due Date: Sept. 28, 2007 Student name: ___________________ Student SISD #: __________________ 1. Which has the greater kinetic energy, an object with a mass of 2.0 kg and a velocity of 1.0 m/s, or an object with a mass of 1.0 kg and a velocity of 2.0 m/s? ANSWER: KE = 1 2 mv 2 = 1 2 x 2.0 kg x 1.0m s 2 = 1.0 J; KE = 1 2 mv 2 = 1 2 x 1.0 kg x 2.0m s 2 = 2.0 J The 1.0 kg object with a velocity of 2.0 m/s has the greater kinetic energy. 2. Consider a mixture of air and gasoline vapor in a cylinder with a piston. The original volume is 40 cm 3 . If the combustion of this mixture releases 950 J of energy, to what volume will the gases expand against a constant pressure of 650 torr if all the energy of combustion is converted into work to push back the piston. ANSWER: In this problem q = w = -950 J L 11.0 = V L, 11.0 = 0.040 - V L), 0.040 - (V x atm 760 650 - = atm L 9.38 - V P . 38 . 9 J 101.3 atm L 1 . 950 f f f = Δ = = w gases the by done work of atm L x J 3. What is a state function? Enthalpy and internal energy are state functions as a direct consequence of the first law of thermodynamics. Why is this so? ANSWER: A state function is a function whose change depends only on the initial and final states and not on how one got from the initial to the final state. If H and E were not state functions, the law of conservation of energy (first law) would not be true.

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4. The enthalpy change for the following reaction is -891 kJ / mol: CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O( l ) Calculate the enthalpy change for each of these cases. a. 1.00 g of methane is burned in an excess of oxygen. b.
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## problemset1withanswers - Chem33-1, C-hour Problem Set 1...

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