ACP Chemistry Exam: Thermodynamics

Name: ______Period: _____ Date: ______This exam is worth 72 points. Only those exams completed in black ink will be graded. Good luck!

1 Which of the following signs on q and w represent a system that is doing work on the surroundings, as well as gaining heat from the surroundings? A) q = +, w = - B) q = -, w = + C) q = +, w = + D) q = -, w = - E) None of these represent the system referenced above.

2) For ΔEsys to always be -, what must be true? A) q = w B) +q > -w C) +w > -q D) -w > +q E) None of the above.

3 Define specific heat capacity. A) the quantity of heat required to raise the temperature of 1 mole of a substance by 1°C B) the quantity of heat required to change a system's temperature by 1°C C) the quantity of heat required to raise the temperature of 1 gram of a substance by 1°C D) the quantity of heat required to raise the temperature of 1 gram of a substance by 1°F E) the quantity of heat required to raise the temperature of 1 liter of a substance by 1°C

4) Which of the following substances (with specific heat capacity provided) would show the greatest temperature change upon absorbing 100.0 J of heat? A) 10.0 g Ag, CAg = 0.235 J/g°C B) 10.0 g H2O, CH2O = 4.18 J/g°C C) 10.0 g ethanol, Cethanol = 2.42 J/g°C D) 10.0 g Fe, CFe = 0.449 J/g°C E) 10.0 g Au, CAu = 0.128 J/g°C

5) Calculate the amount of heat (in kJ) required to raise the temperature of a 79.0 g sample of ethanol from 298.0 K to 385.0 K. The specific heat capacity of ethanol is 2.42 J/g°C. A) 57.0 kJ B) 16.6 kJ C) 73.6 kJ D) 28.4 kJ E) 12.9 kJ

1 6) Identify what a bomb calorimeter measures. A) measures ΔH for aqueous solutions B) measures ΔE for combustion reactions C) measures ΔH for oxidation solutions D) measures ΔT for hydrolysis solutions E) measures ΔE for reduction reactions

7) A 21.8 g sample of ethanol (C2H5OH) is burned in a bomb calorimeter, according to the following reaction. If the temperature rises from 25.0 to 62.3°C, determine the heat capacity of the calorimeter. The molar mass of ethanol is 46.07 g/mol.

C2H5OH(l) + 3 O2(g) → 2 CO2(g) + 3 H2O(g) ΔH°rxn = -1235 kJ

A) 4.99 kJ/°C B) 5.65 kJ/°C C) 63.7 kJ/°C D) 33.1 kJ/°C E) 15.7 kJ/°C

8) Which statement is FALSE? A) An exothermic reaction gives heat off heat to the surroundings. B) Enthalpy is the sum of a system's internal energy and the product of pressure and volume. C) ΔErxn is a measure of heat. D) ΔHrxn is the heat of reaction. E) Endothermic has a positive ΔH.

9) Which of the following processes is endothermic? A) an atom emits a photon B) the condensation of water C) an atom absorbs a photon D) the electron affinity of a fluorine atom E) None of the above processes are endothermic.

10)According to the following reaction, how much energy is evolved during the reaction of 32.5 g B2H6 and 72.5 g Cl2? The molar mass of B2H6 is 27.67 g/mol.

B2H6(g) + 6 Cl2(g) → 2 BCl3(g) + 6 HCl(g) ΔH°rxn = -1396 kJ

A) 1640 kJ B) 238 kJ C) 1430 kJ D) 3070 kJ E) 429 kJ

2 11)Identify what a coffee cup calorimeter measures. A) measures ΔH for aqueous solutions B) measures ΔE for combustion reactions C) measures ΔH for oxidation solutions D) measures ΔT for hydrolysis solutions E) measures ΔE for reduction reactions

12)A piece of iron (mass = 25.0 g) at 398 K is placed in a styrofoam coffee cup containing 25.0 mL of water at 298 K. Assuming that no heat is lost to the cup or the surroundings, what will the final temperature of the water be? The specific heat capacity of iron = 0.449 J/g°C and water = 4.18 J/g°C. A) 348 K B) 308 K C) 287 K D) 325 K E) 388 K

13)Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction:

P4(g) + 10 Cl2(g) → 4PCl5(s) ΔH°rxn = ?

Given:

PCl5(s) → PCl3(g) + Cl2(g) ΔH°rxn= +157 kJ

P4(g) + 6 Cl2(g) → 4 PCl3(g) ΔH°rxn = -1207 kJ

A) -1835 kJ B) -1364 kJ C) -1050. kJ D) -1786 kJ E) -2100. kJ

14)Choose the reaction that illustrates ΔH°f for Ca(NO3)2. A) Ca(s) + N2(g) + 3O2(g) → Ca(NO3)2(s) B) Ca2+(aq) + 2 NO3-(aq) → Ca(NO3)2(aq) C) Ca(s) + 2 N(g) + 6 O(g) → Ca(NO3)2(s) D) Ca(NO3)2(aq) → Ca2+(aq) + 2 NO3-(aq) E) Ca(NO3)2(s) → Ca(s) + N2(g) + 3O2(g)

3 15)Use the ΔH°f and ΔH°rxn information provided to calculate ΔH°f for IF:

ΔH°f (kJ/mol) IF7(g) + I2(g) → IF5(g) + 2 IF(g) ΔH°rxn = -89 kJ IF7(g) -941 IF5(g) -840

A) 101 kJ/mol B) -146 kJ/mol C) -190. kJ/mol D) -95 kJ/mol E) 24 kJ/mol

16) In which of the following processes do the molecules become more orderly? A) water freezing B) ice melting C) water evaporating D) salt dissolving in water E) dry ice subliming

17) Which of the following processes have a ΔS > 0? A) CH3OH(l) → CH3OH(s) B) N2(g) + 3 H2(g) → 2 NH3(g) C) CH4(g) + H2O (g) → CO(g) + 3 H2(g) D) Na2CO3(s) + H2O(g) + CO2(g) → 2 NaHCO3(s) E) All of the above processes have a ΔS > 0.

18) Which of the following processes shows a decrease in entropy of the system? A) 2 NO(g) + O2(g) → 2 NO2(g) B) COCl2(g) → CO(g) + Cl2(g) C) CH3OH(l) → CO(g) + 2H2(g) D) NaClO3(s) →Na+(aq) + ClO3-(aq) E) None of the above will show a decrease in entropy.

19) Consider a reaction that has a positive ΔH and a positive ΔS. Which of the following statements is TRUE? A) This reaction will be spontaneous only at high temperatures. B) This reaction will be spontaneous at all temperatures. C) This reaction will be nonspontaneous at all temperatures. D) This reaction will be nonspontaneous only at high temperatures. E) It is not possible to determine without more information.

4 20) Consider a reaction that has a positive ΔH and a negative ΔS. Which of the following statements is TRUE? A) This reaction will be spontaneous only at high temperatures. B) This reaction will be spontaneous at all temperatures. C) This reaction will be nonspontaneous at all temperatures. D) This reaction will be nonspontaneous only at high temperatures. E) It is not possible to determine without more information.

21) For the following example, identify the following.

H2O (l) → H2O(g)

A) a negative ΔH and a negative ΔS B) a positive ΔH and a negative ΔS C) a negative ΔH and a positive ΔS D) a positive ΔH and a positive ΔS E) It is not possible to determine without more information

22) Above what temperature does the following reaction become nonspontaneous?

FeO(s) + CO(g) → CO2(g) + Fe(s) ΔH = -11.0 kJ; ΔS = -17.4 J/K

A) 632 K B) 298 K C) 191 K D) This reaction is nonspontaneous at all temperatures. E) This reaction is spontaneous at all temperatures.

23) Identify the statement that is FALSE. A) The entropy of a gas is greater than the entropy of a liquid. B) Entropy generally increases with increasing molecular complexity. C) Free atoms have greater entropy than molecules. D) Entropy increases with dissolution. E) For noble gasses, entropy increases with size.

24) Place the following in order of decreasing standard molar entropy.

N2O4 (g) NO (g) NO2 (g)

A) N2O4 > NO2 > NO B) NO > NO2 > N2O4 C) N2O4 > NO > NO2 D) NO > N2O4 > NO2 E) NO2 > NO > N2O4

5 25) Calculate ΔS°rxn for the following reaction. The S° for each species is shown below the reaction.

C2H2(g) + H2(g) → C2H4(g) S°(J/mol∙K) 200.9 130.7 219.3

A) +112.3 J/K B) +550.9 J/K C) -112.3 J/K D) +337.1 J/K E) -550.9 J/K

26) Identify the compound with the lowest standard free energy of formation. A) NaCl(s) B) N2(g) C) NO(g) D) O3(g) E) It is hard to determine.

27) Give the name of the reaction that achieves the theoretical limits with respect to free energy in thermodynamics. A) reversible reaction B) forward reaction C) reverse reaction D) equilibrium reaction E) irreversible reaction

28) Given the following equation,

N2O(g) + NO2(g) → 3 NO(g) ΔG°rxn = -23.0 kJ

Calculate ΔG°rxn for the following reaction.

9 NO(g) → 3N2O(g) + 3NO2(g)

A) -23.0 kJ B) 69.0 kJ C) -69.0 kJ D) -7.67 kJ E) 23.0 kJ

6 29) Determine ΔG°rxn using the following information.

CaCO3(s) → CaO(s) + CO2(g) ΔH°= +179.2 kJ; ΔS°= +160.2 J/K

A) -607.0 kJ B) +112 .0 kJ C) -89.3 kJ D) +131.4 kJ E) +228.1 kJ

30) Calculate the ΔG°rxn using the following information.

2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l) ΔG°rxn = ? ΔG°f (kJ/mol) -110.9 87.6 51.3 -237.1

A) -162.5 kJ B) +51.0 kJ C) -54.5 kJ D) +171.1 kJ E) -87.6 kJ

31) Use Hess's law to calculate ΔG°rxn using the following information. NO(g) + O(g) → NO2(g) ΔG°rxn = ?

2 O3(g) → 3 O2(g) ΔG°rxn = +489.6 kJ O2(g) → 2 O(g) ΔG°rxn = +463.4 kJ NO(g) + O3(g) → NO2(g) + O2(g) ΔG°rxn = - 199.5 kJ

A) +753.5 kJ B) +277.0 kJ C) -676.0 kJ D) -1152.5 kJ E) -225.7 kJ

32) Estimate ΔG°rxn for the following reaction at 449.0 K.

CH2O(g) + 2 H2(g) → CH4(g) + H2O(g) ΔH°= -94.9 kJ; ΔS°= -224.2 J/K

A) +5.8 kJ B) +12.9 kJ C) -101 kJ D) +2.4 kJ E) -4.2 kJ

7 33) Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction.

2 Hg(g) + O2(g) → 2 HgO(s) ΔG° = -180.8 kJ

P(Hg) = 0.025 atm, P(O2) = 0.037 atm

A) +207 kJ B) -154.4 kJ C) -26.5 kJ D) -164 kJ E) +60.7 kJ

34) Choose the statement below that is TRUE. A) K > 1, ΔG°rxn is positive. B) K < 1, ΔG°rxn is negative. C) ΔG°rxn = 0 at equilibrium. D) ΔGrxn = 0 at equilibrium. E) None of the above statements are true.

35) What is true if ln K is negative? A) ΔGorxn is positive and the reaction is spontaneous in the forward direction. B) ΔGorxn is negative and the reaction is spontaneous in the forward direction. C) ΔGorxn is negative and the reaction is spontaneous in the reverse direction. D) ΔGorxn is positive and the reaction is spontaneous in the reverse direction. E) ΔGorxn is zero and the reaction is at equilibrium.

36) Determine the equilibrium constant for the following reaction at 298 K.

Cl(g) + O3(g) → ClO(g) + O2(g) ΔG° = - 34.5 kJ

A) 5.66 × 105 B) 0.986 C) 8.96 × 10-7 D) 4.98 × 10-4 E) 1.12 × 106