2008 mid - CHM 2132 Midterm 1/10 Name: Student Number: CHM...

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CHM 2132 Midterm 1/10 Name: Student Number: CHM 2132 Midterm Test, October 24 th 2008 This is a closed book exam with no notes allowed. Calculators are permitted. Write all the formulas that you use to solve the questions and show all your work. Remember to include units in all your calculations . Marks will be deducted if units are not shown. Data section and equation sheet available at the end of the exam. You can remove these pages and keep them. Maximum score = 58/55 points Please note that when re- marking, I will look at the full exam.
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CHM 2132 Midterm 2/10 1. (11 points) 10 g of ethanol vapour (C 2 H 5 OH) is combusted under standard pressure at 298 K. a) What is the total enthalpy of combustion for this reaction? C 2 H 5 OH(g) + 3 O 2 (g) 2 CO 2 (g) + 3 H 2 O(l) Δ r H m ° = v Δ f H m ° Products v Δ f H m ° Reactants = 3 Δ f H m ° H 2 O (l) () + 2 Δ f H m ° CO 2 (l) −Δ f H m ° C 2 H 5 OH (l) 3 Δ f H m ° O 2 (l) ( ) = 3 285.83 kJ mol -1 + 2 393.51 kJ mol -1 −− 235.10 kJ mol -1 =− 1409.41 kJ mol -1 Δ r H o = n Δ r H m ° = m M ×Δ r H m ° = 10 g 46.07 g mol -1 1409.41 kJ mol -1 ( ) 310 kJ mol -1 kJ, not per mol b) What would the total enthalpy be for combustion of liquid ethanol at the same temperature? Δ r H m ° liquid ethanol r H m ° ethanol vapor vap H m ° liquid ethanol ( ) 1409.41 kJ mol -1 + 43.5 kJ mol -1 1365.91 kJ mol -1 Δ r H o = n Δ r H m ° = m M r H m ° = 10 g 46.07 g mol -1 1365.91 kJ mol -1 ( ) 296 kJ mol -1 kJ, not per mol c) What would be the total enthalpy for the combustion of the vapour at 350 K? () () Δ Δ + Δ = Δ T C T C T H T H react p prod p 1 r 2 r ) 298 350 ( / 44 . 64 ) 298 350 )( / 36 . 29 ( 3 ) 298 350 )( / 11 . 37 ( 2 ) 298 350 ( / 1 . 89 / 1409410 350 + + = Δ Kmol J Kmol J Kmol J K K Kmol J mol J H r Kmol J H r / 1409160 88 . 3350 16 . 4580 44 . 3547 2 . 4633 1409410 350 = + + = Δ
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CHM 2132 Midterm 3/10 () kJ H g for Kmol kJ H r r 87 . 305 350 10 / 16 . 1409 350 = Δ = Δ 2. (5 points) Estimate the standard enthalpy of formation of (CH 3 ) 3 C-CClH-CH 3 using Benson thermochemical groups. From left to right: ( ) ( ) ( )( ) ( )( ) ( ) C H C H C H Cl C H C C H C H C H H f f f f f 3 2 4 3 3 Δ + Δ + Δ + Δ = Δ ( ) ( ) 17 . 42 2 . 60 16 . 8 17 . 42 3 + + + = Δ H f mol kJ H f / 7 . 220 = Δ 3. (12 points) a) Each one of the loops below represents a heat engine. Explain in ONE sentence which engine is capable of producing more work and why. The magnitude of work is given by the area inside the loop, therefore loop C is the one capable of producing more work. b) Mark the following statements as true or false. NOTE: YOU WILL LOOSE MARKS FOR INCORRECT ANSWERS. T/F a) The internal energy of an ideal gas is independent of temperature. F A B C V p
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CHM 2132 Midterm 4/10 b) The total entropy of the universe is always increasing. T c) A gas that expands spontaneously and irreversibly against an external pressure is performing work.
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This note was uploaded on 11/13/2010 for the course CHM CHM2132 taught by Professor Goto during the Fall '07 term at University of Ottawa.

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2008 mid - CHM 2132 Midterm 1/10 Name: Student Number: CHM...

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