Physical Chemistry I Exam points

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1 Chemistry 360 Fall 2018 Dr. Jean M. tandard October 17, 2018 Name Physical Chemistry I Exam points Note: You must show your work on problems in order to receive full credit for any answers. You must turn in your equation sheet along with this exam in order to receive full credit for the exam. Please turn off cell phones and store them during the exam. 1.) (14 points) Determine # H & $ P ' T for a gas obeying the equation of state Z = PV m RT = 1 + BP + CP 2, where B and C are constants.

2 2 2.) (14 points) The standard molar enthalpy of formation of Fe 2 O 3 (s) is ΔH f = kj/mol, and the standard molar enthalpy of formation of O 2 (g) is ΔH f = kj/mol (both at 298 K). Use this information, along with the standard molar enthalpy change of the following reaction at 298 K, 2 Fe 2 (s) O 2 (g) Fe 2 O 3 (s) + 4 O 2 (g) ΔH R = 1655 kj/mol, to determine the standard molar enthalpy change of the reaction shown below at 298 K: Fe (s) + 2 (s) Fe 2 (s). [Note: The standard state of iron is Fe(s) and the standard state of sulfur is (s) at 298 K.]

3 3.) (14 points) Explain why we are able to obtain absolute molar entropies of substances; that is, what is the theoretical foundation that allows the determination of absolute molar entropies? Discuss any trends that may be observed in the magnitudes of the absolute molar entropies of the following substances and the reasoning behind your answer: He (g), O 2 (g), CH 4 (g), C 6 H 6 (g). 3

4 4.) (15 points) True/false, short answer, multiple choice. 4 a.) True or False: In the statistical definition of entropy, = k B lnw, the quantity W corresponds to the energy. b.) True or False: The Debye equation gives the form of the constant pressure molar heat capacity of a solid at low temperature and has the form C p,m ( T ) = at 2. c.) hort answer calorimetry is carried out at constant volume, whereas calorimetry is carried out at constant pressure. d.) hort answer For two chemical reactions that combine to give a third reaction (the overall reaction), the enthalpy change of the overall reaction (3) is given as ΔH 3 = ΔH 1 + ΔH 2, which is an example of the application of. e.) Multiple Choice: Which of the following corresponds to the correct relationship? 1) T = G $ # &. " P % " 2) T = U % $ '. # V & " 3) T = A % $ '. # V & 4) T = H $ # &. " % P

5 5.) (14 points) Using the values in the table below reported at 298 K, determine ΔH R hydrogenation of acetylene to ethane, C 2 H 2 ( g) + 2 H 2 g ( ) C 2 H 6 ( g). at 700 K for the 5 Assume that C p,m is independent of temperature for all species in the reaction. ΔH f C p,m (kj/mol) (Jmol 1 K 1 ) C 2 H 2 (g) C 2 H 6 (g) H 2 (g)

6 6.) (14 points) Calculate the entropy change Δ for the following transformation involving one mole of H 2 O, 6 H 2 O (s, 200 K) H 2 O (l, 300 K). You may need to use the following data: T fus = 273 K ; ΔH fus = 6.01 kj mol 1 T vap = 373 K; ΔH vap = kj mol 1 C p,m s ( ) = 36.2 J mol 1 K 1 ; C p,m ( l) = 75.3 J mol 1 K 1 ; C p,m ( g) = 33.6 J mol 1 K 1

7 7.) (15 points) True/false, short answer, multiple choice. 7 a.) True or False: For the reaction 2 CO (g) + O 2 (g) 2 CO 2 (g), the entropy change is expected to be negative. b.) True or False: The standard state is defined to be the pure form of an element at 1 bar and 25 C. c.) hort answer The states that entropy increases for a spontaneous process in an isolated system. d.) hort answer The is defined as U T. e.) Multiple Choice: At 298 K, ΔG R = 158 kj/mol for a certain chemical reaction. In addition, this reaction has ΔH R > 0. Which of the following is a reasonable expectation for ΔG R at 500 K? 1) ΔG R = 195 kj/mol. 2) ΔG R = 158 kj/mol. 3) ΔG R = 141 kj/mol. 4) ΔG R = +158 kj/mol.

8 8 PHYICAL CONTANT, CONVERION FACTOR, AND EQUATION R = L atm mol 1 K 1 = J mol 1 K 1 = L bar mol 1 K 1 = L torr mol 1 K 1 1 atm = Pa = bar = 760 torr 1 bar = 10 5 Pa = atm 1 L atm = J; 1 L bar = 100 J 1 cal = J Fundamental Equations du = T d P dv dh = T d + V dp da = dt P dv dg = dt + V dp Maxwell Relations # T & $ V ' # T & $ P ' # & $ V ' T # & $ P ' T # = P & $ ' # = V & $ ' # = P & $ T ' P V V # = V & $ T ' P

Exam 2 Solutions. for a gas obeying the equation of state. Z = PV m RT = 1 + BP + CP 2,

Exam 2 Solutions. for a gas obeying the equation of state. Z = PV m RT = 1 + BP + CP 2, Chemistry 360 Dr. Jean M. Standard Fall 016 Name KEY 1.) (14 points) Determine # H & % ( $ ' Exam Solutions for a gas obeying the equation of state Z = V m R = 1 + B + C, where B and C are constants. Since