Thermochemistry HW PSI Chemistry Name Energy 1) Objects can possess energy as: (a) endothermic energy (b) potential energy A) a only B) b only C) c only D) a and c E) b and c (c) kinetic energy 2) The internal energy of a system A) is the sum of the kinetic energy of all of its components B) is the sum of the rotational, vibrational, and translational energies of all of its components C) refers only to the energies of the nuclei of the atoms of the component molecules D) is the sum of the potential and kinetic energies of the components E) none of the above 3) Which one of the following conditions would always result in an increase in the internal energy of a system? A) The system loses heat and does work on the surroundings. B) The system gains heat and does work on the surroundings. C) The system loses heat and has work done on it by the surroundings. D) The system gains heat and has work done on it by the surroundings. E) None of the above is correct. 4) The value of ΔE for a system that performs 111 kj of work on its surroundings and gains 89 kj of heat is kj. A) -111 B) -200 C) 200 D) -22 E) 22 5) The value of ΔE for a system that performs 13 kj of work on its surroundings and loses 9 kj of heat is kj. A) 22 B) -22 C) -4 D) 4 E) -13 6) Calculate the value of ΔE in joules for a system that loses 50 J of heat and has 150 J of work performed on it by the surroundings. A) 50 B) 100 C) -100 D) -200
E) +200 7) The change in the internal energy of a system that absorbs 2,500 J of heat and that does 7,655 J of work on the surroundings is J. A) 10,155 B) 5,155 C) -5,155 D) -10,155 E) 1.91 x10 7 8) The change in the internal energy of a system that releases 2,500 J of heat and that does 7,655 J of work on the surroundings is J. A) -10,155 B) -5,155 C) -1.91x10 7 D) 10,155 E) 5,155 9) When a system, ΔE is always negative. A) absorbs heat and does work B) gives off heat and does work C) absorbs heat and has work done on it D) gives off heat and has work done on it E) none of the above is always negative. 10) Of the following, which one is a state function? A) H B) q C) w D) heat E) none of the above Energy Changes 11) Which one of the following is an endothermic process? A) ice melting B) water freezing C) boiling soup D) Hydrochloric acid and barium hydroxide are mixed at 25 C: the temperature increases. E) Both A and C 12) Which one of the following is an exothermic process? A) ice melting B) water evaporating C) boiling soup D) condensation of water vapor E) Ammonium thiocyanate and barium hydroxide are mixed at 25 C: the temperature drops. 13) A ΔH corresponds to an process. A) negative, endothermic B) negative, exothermic
C) positive, exothermic D) zero, exothermic E) zero, endothermic 14) A ΔH corresponds to an process. A) negative, endothermic B) positive, exothermic C) positive, endothermic D) zero, exothermic E) zero, endothermic zero, endothermic 15) ΔH for an endothermic process is while ΔH for an exothermic process is. A) zero, positive B) zero, negative C) positive, zero D) negative, positive E) positive, negative 16) A chemical reaction that absorbs heat from the surroundings is said to be and has a ΔH. A) endothermic, positive B) endothermic, negative C) exothermic, negative D) exothermic, positive E) exothermic, neutral 17) The reaction 4Al(s) + 3O2 (g) 2Al2O3 (s) ΔH = -3351 kj is, and therefore heat is by the reaction. A) endothermic, released B) endothermic, absorbed C) exothermic, released D) exothermic, absorbed E) thermoneutral, neither released nor absorbed Calorimetry *18) The molar heat capacity of a compound with the formula C2H6SO is 88.0 J/mol-K. The specific heat of this substance is J/g-K. A) 88.0 B) 1.13 C) 4.89 D) 6.88x10 3 E) -88.0 19) A sample of aluminum metal absorbs 9.86 J of heat, and the temperature of the sample increases from 23.2 C to 30.5 C. Since the specific heat capacity of aluminum is 0.90 J/g- K, the mass of the sample is g. A) 72 B) 1.5 C) 65 D) 8.1
E) 6.6 20) The specific heat capacity of lead is 0.13 J/g-K. How much heat (in J) is required to raise the temperature of 15g of lead from 22 C to 37 C? A) 2.0 B) -0.13 C) 5.8 x10-4 D) 29 E) 0.13 21) The temperature of a 15-g sample of lead metal increases from 22 C to 37 C upon the addition of 29.0 J of heat. The specific heat capacity of the lead is J/g-K. A) 7.8 B) 1.9 C) 29 D) 0.13 E) -29 *22) The ΔH for the solution process when solid sodium hydroxide dissolves in water is 44.4 kj/mol. When a 13.9-g sample of NaOH dissolves in 250.0 g of water in a coffee-cup calorimeter, the temperature increases from 23.0 C to C. Assume that the solution has the same specific heat as liquid water, i.e., 4.18 J/g-K. A) 35.2 C B) 24.0 C C) 37.8 C D) 37.0 C E) 40.2 C 23) An 8.29 g sample of calcium carbonate [CaCO3(s)] absorbs 50.3 J of heat, upon which the temperature of the sample increases from 21.1 C to 28.5 C. What is the specific heat of calcium carbonate? A).63 B).82 C) 1.1 D) 2.2 E) 4.2 24) A sample of iron absorbs 67.5 J of heat, upon which the temperature of the sample increases from 21.5 C to 28.5 C. If the specific heat of iron is 0.450 J/g-K, what is the mass (in grams) of the sample? A) 4.3 B) 11 C) 21 D) 1100 E) 1.1x 10 3 25) A 22.44 g sample of iron absorbs 180.8 J of heat, upon which the temperature of the sample increases from 21.1 C to 39.0 C. What is the specific heat of iron? A) 0.140 B) 0.450
C) 0.820 D) 0.840 E) 0.900 26) When 45 g of an alloy at 100 0C is dropped into 100.0 g of water at 25 C, the final temperature is 37 C. What is the specific heat of the alloy (J/g o C)? 31) A)9.88 B) 48.8 C) 0.423 D) 1.77 *27) A 50.0-g sample of liquid water at 25.0 C is mixed with 29.0 g of water at 45.0 C. The final temperature of the water is. A) 102 B) 27.6 C) 35.0 D) 142 E) 32.3 28) A 6.50-g sample of copper metal at 25.0 C is heated by the addition of 84.0 J of energy. The final temperature of the copper is C. The specific heat of copper is 0.38 J/g-K A) 29.9 B) 25.0 C) 9.0 D) 59.0 E) 34.0 Heating curves 29) How much heat is required to melt 1.5 moles of NaCl at its melting point ( Hfus = 30 kj/mol) A) 1.5 kj B) 15 kj C) 20 kj D) 30 kj E) 45 kj 30) A substance releases 500 kj of heat as 25 mol of it condenses from a gas to a liquid. What is the heat of vaporization ( Hvap) of this substance? A) 20 kj/mol B) 25 kj/mol C) 475 kj/mol D) 525 kj/mol **31) If you supply 36 kj of heat, how many moles of ice a 0 o C can be melted, heated to its boiling point and completely boiled away? Hvap = 40.5 kj/mol; Hfus = 6.0 kj/mol; specific heat for water, C = 0.0753 kj/mol- o C
**32) Given the equation: H2O (l) H2O(g) Hrxn = 40.7 kj at 100 C Calculate the mass of liquid water (in grams) at 100 C that can converted to vapor by absorbing 2.40 kj of heat. 33) Given the equation: H2O (l) H2O(g) Hrxn = 40.7 kj at 100 C Calculate the heat required to convert 3.00 grams of liquid water at 100 C to vapor. *34) Based on the following information, which compound has the strongest intermolecular forces? Substance ΔH vap (kj/mol) Argon (Ar) 6.3 Benzene ( CH 6 6) 31.0 Ethanol ( C2H5OH ) 39.3 Water ( HO) 2 40.8 Methane ( CH 4 ) 9.2 A) Argon B) Benzene C) Ethanol D) Water E) Methane Use the information in this table to answer the next four questions. Specific heat of ice Specific heat of water Specific heat of steam Heat of fusion of water ( Hfus) Heat of vaporization of water ( Hvap) 2.09 J/g- o C 4.18 J/g- o C 1.84 J/g- o C 6.01 kj/mol 40.7 kj/mol 35) What amount of heat (in kj) is required to melt 35.0 g of ice at 0 o C? A) 3.09 kj B) 11.7 kj C) 20.9 kj D) 79.1 kj 36) What amount of heat (in kj) is required to completely convert 190.0 g of liquid water at 18 o C to steam at 100.0 o C? A) 6.51 kj B) 6.94 kj C) 430 kj D) 559 kj
37) The enthalpy change for converting 1.00 mol of ice at -50.0 C to water at 70.0 C is kj. A) 12.28 B) 6.41 C) 13.16 D) 7154 E) 9.40 38) The enthalpy change for converting 10.0 g of ice at -25.0 C to water at 80.0 C is kj. A) 12.28 B) 6.16 C) 3870 D) 7.21 E) 9.88 **39) The heat of fusion of water is 6.01 kj/mol. The heat capacity of liquid water is 75.3 J/mol-K The conversion of 50.0 g of ice at 0.00 C to liquid water at 22.0 C requires kj of heat. A) 3.8 x10 2 B) 21.3 C) 17.2 D) 0.469 E) Insufficient data are given. Enthalpy 40) Which of the following statements is false? A) Internal energy is a state function. B) Enthalpy is an intensive property. C) The enthalpy change for a reaction is equal in magnitude, but opposite in sign, to the enthalpy change for the reverse reaction. D) The enthalpy change for a reaction depends on the state of the reactants and products. E) The enthalpy of a reaction is equal to the heat of the reaction. 41) The value of H 0 for the reaction below is -72 kj. kj of heat are released when 1.0 mol of HBr is formed in this reaction: H2(g) + Br2 (g) 2HBr(g) A) 144 B) 72 C) 0.44 D) 36 E) -72 42) The value of H 0 for the reaction below is -126 kj. kj are released when 2.00 mol of NaOH is formed in the reaction? 2Na2O2(s) + 2H2O(l) 4NaOH(s) + O2(g) A) 252 B) 63 C) 3.9
D) 7.8 E) -126 43) The value of H 0 for the reaction below is -790 kj. The enthalpy change accompanying the reaction of 0.95 g of S is kj. 2S(s) + 3O2 (g) 2SO3(g) A) 23 B) -23 C) -12 D) 12 E) -790 44) The value of H 0 for the reaction below is -6535 kj. kj of heat are released in the combustion of 16.0 g of C6H6(l)? 2C6H6(l) + 15O2 (g) 12CO2 (g) + 6H2O(l) A) 1.34 x 10 3 B) 5.23 x01 4 C) 669 D) 2.68 x10 3 E) -6535 45) The value of H 0 for the reaction below is -482 kj. Calculate the heat (kj) released to the surroundings when 12.0 g of CO (g) reacts completely. 2CO(g) + O2(g) 2CO2(g) A) 2.89x10 3 B) 207 C) 103 D) 65.7 E) -482 46) The value of H 0 for the reaction below is -336 kj. Calculate the heat (kj) released to the surroundings when 23.0 g of HCl is formed. CH4(g) +3Cl2 (g) CHCl3(l) + 3HCl(g) A) 177 B) 2.57x10 3 C) 70.7 D) 211 E) -336 47) The value of H 0 for the reaction below is -186 kj. Calculate the heat (kj) released from the reaction of 25 g of Cl2. H2 (g) + Cl2 (g) 2HCl (g) A) 66 B) 5.3x10 2 C) 33 D) 47 E) -186 48) The enthalpy change for the following reaction is -483.6 kj: 2H2 (g) + O2 (g) 2H2O(g) Therefore, the enthalpy change for the following reaction is kj: 4H2 (g) + 2O2 (g) 4H2O(g) A) -483.6 B) -967.2 C) 2.34x10 5
D) 483.6 E) 967.2 49) The value of H for the reaction below is +128.1 kj: CH3OH (l) CO(g) + 2H2(g) How many kj of heat are consumed when 15.5 g of CH3OH(l) decomposes as shown in the equation? A) 0.48 B) 62.0 C) 1.3x10 2 D) 32 E) 8.3 50) The value of H 0 for the reaction below is +128.1 kj: CH3OH (l) CO(g) + 2H2(g) How many kj of heat are consumed when 5.10 g of H2(g) is formed as shown in the equation? A) 162 B) 62.0 C) 128 D) 653 E) 326 51) The value of H 0 for the reaction below is +128.1 kj: CH3OH (l) CO(g) + 2H2(g) How many kj of heat are consumed when 5.10 g of CO (g) are formed? A) 0.182 B) 162 C) 8.31 D) 23.3 E) 62.0 52) The value of H 0 for the reaction below is +128.1 kj: CH3OH (l) CO(g) + 2H2(g) How many kj of heat are consumed when 5.75 g of CO(g) is formed? A) 23.3 B) 62.0 C) 26.3 D) 162 E) 8.3 53) The value of H 0 for the reaction below is -1107 kj: 2Ba(s) + O2 (g) 2BaO (s) How many kj of heat are released when 5.75 g of Ba(s) reacts completely with oxygen to form BaO(s)? A) 96.3 B) 26.3 C) 46.4 D) 23.2 E) 193 54) The value of H 0 for this reaction is -1107 kj: 2Ba(s) + O2 (g) 2BaO (s) How many kj of heat are released when 5.75 g of BaO(s) is produced? A) 56.9 B) 23.2
C) 20.8 D) 193 E) 96.3 55) The value of H 0 for the reaction below is -1107 kj: 2Ba(s) + O2 (g) 2BaO (s) How many kj of heat are released when 15.75 g of Ba(s) reacts completely with oxygen to form BaO(s)? A) 20.8 B) 63.5 C) 114 D) 70.3 E) 35.1 Hess Law of Heat Summation 56) Which of the following is a statement of Hess's law? A) If a reaction is carried out in a series of steps, the ΔH for the reaction will equal the sum of the enthalpy changes for the individual steps. B) If a reaction is carried out in a series of steps, the ΔH for the reaction will equal the product of the enthalpy changes for the individual steps. C) The ΔH for a process in the forward direction is equal in magnitude and opposite in sign to the ΔH for the process in the reverse direction. D) The ΔH for a process in the forward direction is equal to the ΔH for the process in the reverse direction. E) The ΔH of a reaction depends on the physical states of the reactants and products. *57) ΔH for the reaction IF5 (g) IF3 (g) + F2 (g) is kj, give the data below. IF (g) + F2(g) IF3 (g) ) ΔH = -390 kj IF (g) + 2F2(g) IF5 (g) ΔH = -745 kj A) +355 B) -1135 C) +1135 D) +35 E) -35 *58) Given the following reactions the enthalpy of the reaction of the nitrogen to produce nitric oxide N2 (g) + O2(g) 2NO (g) is kj. N2 (g) + 2O2(g) 2NO2 (g) ΔH = 66.4 kj 2NO (g) + O2(g) 2NO2 (g) ΔH = -114.2 kj A) 180.6 B) -47.8 C) 47.8 D) 90.3 E) -180.6 *59) Given the following reactions the enthalpy of the reaction of nitrogen with oxygen to produce nitrogen dioxide N2 (g) + 2O2(g) 2NO2 (g) is kj.
A) 68 B) -68 C) -292 D) 292 E) -146 (1) 2NO N2 + O2 ΔH = -180 kj (2) 2NO + O2 2NO2 ΔH = -112 kj *60) Given the following reactions the enthalpy of the reaction CaCO3 (s) CaO(s) + C (s) + O2 (g) is kj. CaCO3 (s) CaO(s) + CO2(g) ΔH = 178.1 kj C(s) + O2 (g) CO2(g) ΔH = -393.5 kj A) 215.4 B) 571.6 C) -215.4 D) -571.6 E) 7.01x10 4 *61) Given the following reactions the enthalpy for the decomposition of liquid water into gaseous hydrogen and oxygen 2H2O (l) 2H2 (g) + O2(g) is kj. H2O (l) H2O (g) ΔH = 44.01 kj 2H2 (g) O2(g) 2H2O (g) ΔH = -483.64 kj A) -395.62 B) -527.65 C) 439.63 D) 571.66 E) 527.65 *62) Given the following reactions the enthalpy for the decomposition of nitrogen dioxide into molecular nitrogen and oxygen 2NO2 (g) N2(g) + 2O2 (g) is kj. N2 (g) O2(g) 2NO(g) ΔH = +180.7 kj 2NO (g) + O2 (g) 2NO2 (g) ΔH = -113.1 kj A) 67.6 B) -67.6 C) 293.8 D) -293.8 E) 45.5 *63) Given the following reactions the enthalpy of reaction for 4NO(g) 2NO2 (g) + N2 (g) is kj. N2 (g) + O2(g) 2NO (g) ΔH = +180.7 kj 2NO(g) +O2 (g) 2NO2 (g) ΔH = -113.1 kj A) 67.6 B) 45.5 C) -293.8 D) -45.5
E) 293.8 *64) Given the following reactions the enthalpy of reaction for 2N2O(g) 2NO(g) +N2(g) is kj. N2 (g) + O2(g) 2NO(g) ΔH = +180.7 kj 2N2O(g) O2 (g) + 2N2(g) ΔH = -163.2 kj A) 145.7 B) 343.9 C) -343.9 D) 17.5 E) -145.7 Heats of Formation 65) Of the following, ΔHf 0 is not zero for. A) O2(g) B) C (graphite) C) N2(g) D) F2 (s) E) Cl2(g) 66) In the reaction below, ΔHf 0 is zero for. Ni(s) + 2CO (g) +2PF3 (g) Ni(CO)2 (PF3)2(l) A) Ni(s) B) CO(g) C) PF3(g) D) Ni(CO)2 (PF3)2(l) E) both CO and PF3 67) For the species in the reaction below, ΔHf 0 is zero for. 2Co(s) + H2(g) + 8PF3 (g) 2HCo(PF3)4 (I) A) Co(s) B) H2(g) C) PF3 (g) D) HCo(PF3)4 E) both Co(s) and H2(g) **68) For which one of the following equations is ΔH 0 rxn equal to ΔHf 0 for the product? A) Xe (g) + 2F2 (g) XeF4 (g) B) CH4 (g) +2Cl2(g) CH2Cl2 (l) + 2HCl(g) C) N2(g) + O3 (g) N2O3 (g) D) 2CO(g) +O2(g) 2CO2 E) C(diamond) + O2(g) CO2 (g) **69) For which of the following reactions is the value of ΔH 0 rxn equal to ΔHf 0 for the product? A) 2Ca(s) + O2 (g) 2CaO(s) B) C2H2(g) + H2(g) C2H4 (g)
C) 2C(graphite) +O2(g) 2CO (g) D) 3Mg(s) + N2(g) Mg3N2(s) E) C(diamond) + O2(g) CO2 (g) **70) For which of the following reactions is the value of ΔH 0 rxn equal to ΔHf 0 for the product? A) 2C(graphite) + 2H2(g) C2H4(g) B) N2(g) +O2(g) 2NO(g) C) 2H2(g) +O2(g) 2H2O(l) D) 2H2(g) + O2(g) 2H2O(g) E) H2O(l) +1/2 O2(g) 2H2O(l) 71) For which of the following reactions is the value of ΔH 0 rxn equal to ΔHf 0 for the product? A) H2O(l) +1/2 O2(g) H2O2(l) B) N2(g) +O2(g) 2NO(g) C) 2H2(g) + O2(g) 2H2O(l) D) 2H2(g) + O2(g) 2H2O(g) E) none of the above 72) For which of the following reactions is the value of ΔH 0 rxn equal to ΔHf 0 for the product? A) H2(g) + 1/2O2(g) H2O(l) B) H2(g) + O2(g) H2O2 (l) C) 2C(graphite) + 2H2(g) C2H4(g) D) 1/2N2(g) + O2(g) NO2(g) E) all of the above 73) The value of H for the reaction below is -186 kj. The value of ΔHf 0 for HCl (g) is kj/mol. A) -3.72x10 2 B) -1.27x10 2 C) -93.0 D) -186 E) +186 H2(g) + Cl2(g) 2HCl(g) 74) The value of H for the following reaction is -3351 kj: 2Al(s) +3O2(g) 2Al2O3 The value of ΔHf 0 for Al2O3 is kj. A) -3351 B) -1676 C) -32.86 D) -16.43 E) +3351 75) Given the data in the table below, ΔH 0 rxn for this reaction is kj. Ca(OH)2 + 2H3AsO4 Ca(H2AsO4)2 + 2H2O Substance ΔH f 0 (kj/mol)
A) -744.9 B) -4519 C) -4219 D) -130.4 E) -76.4 Ca(OH) 2-986.6 H 3AsO 4-900.4 Ca(H 2AsO 4) 2-2346.0 H 2O -285.9 76) Given the data in the table below, ΔH 0 rxn for this reaction is kj. 4NH3 (g) + 5O2)g) 4NO(g) + 6H2O(l) 0 Substance ΔH f (kj/mol) H 2O(l) -286 NO (g) 90 NO 2 (g) 34 HNO 3 (aq) -207 NH 3 (g) -46 A) -1172 B) -150 C) -1540 D) -1892 E) The ΔHf 0 of O 2(g) is needed. 77) Given the data in the table below, ΔH 0 rxn for this reaction is kj. C2H5OH(l) +O2(g) CH3CO2H(l) + H2O(l) Substance ΔHf 0 (kj /mol) C 2H 4(g) 523 C 2H 5OH(l) -277.7 CH 3CO 2H(l) -484.5 H 2O(l) -285.8 A) -79.0 B) -1048.0 C) -476.4 D) -492.6 E) The value of ΔHf 0 of O 2(g) is required 78) Given the data in the table below, ΔH 0 rxn for this reaction is kj. 3NO2 +H2O (l) 2HNO3 (aq) + NO(g) 0 Substance ΔH f (kj/mol) A) 64 B) 140 C) -140 D) -508 E) -64 H 2O(l) -286 NO (g) 90 NO 2 (g) 34 HNO 3 (aq) -207 NH 3 (g) -46
79) Given the data in the table below, ΔH 0 rxn for this reaction is kj. IF5(g) + F2(g) IF7(g) A) 1801 B) -1801 C) 121 D) -121 E) -101 Substance ΔHf 0 (kj /mol) IF(g) -95 IF5(g) -840 IF7(g) -941 80) Given the data in the table below, H for the reaction is kj. 2CO (g) + O2 2CO2(g) A) -566.4 B) -283.2 C) 283.2 D) -677.0 E) The ΔHf 0 of O 2(g) is needed Substance 0 ΔH f (kj /mol) CO(g) -110.5 CO 2(g) -393.7 CaCO 3(s) -1207.0 *81) The value of ΔH for the following reaction is 177.8 kj. The value of ΔHf 0 for CaO(s) is kj/mol. CaCO3(s) CaO(s) + CO2(g) Substance 0 ΔH f (kj /mol) CO(g) -110.5 CO 2(g) -393.7 CaCO 3(s) -1207.0 A) -1600 B) -813.4 C) -635.5 D) 813.4 E) 177.8 82) Given the data in the table below, ΔH 0 rxn for the reaction is kj. 2Ag2S(s) +O2(g) 2Ag2O(s) +2S(s) Substance ΔH f 0 (kj /mol) Ag 2O(s) -31.0 Ag 2S(s) -326 H 2S(g) -20.6 H 2O(l) -286 A) -1.6 B) +1.6 C) -3.2 D) +3.2 E) The ΔHf 0 of S(s) and of O2(g) are needed.
83) Given the data in the table below, ΔH 0 rxn for the reaction is kj. PCl3(g) +3HCl(g) 3Cl2(g) +PH3(g) 0 Substance ΔH f (kj /mol) PCl 3(g) -288.07 HCl(g) -92.30 PH 3(g) 5.40 A) -570.37 B) -385.77 C) 570.37 D) 385.77 E) The ΔHf 0 of Cl2(g) is needed for the calculation.. *84) Given the data in the table below and ΔH 0 rxn for the reaction, ΔHf 0 of HCl(g) is kj/mol. SO2Cl2(g) +2H2O(l) H2SO4(l) + 2HCl(g) ΔHf 0 = -62 kj 0 Substance ΔH f (kj /mol) SO 2(g) -297 SO 3(g) -396 SO 2Cl 2(g) -364 H 2SO 4(l) -814 H 2O(l) -286 A) -184 B) 60 C) -92 D) 30 E) Insufficient data are given.
Energy 1) E 2) D 3) D 4) D 5) B 6) B 7) C 8) A 9) B 10) A 11) E 12) D 13) B 14) C 15) E 16) A 17) C Calorimetry 18) B 19) B 20) D 21) D 22) D 23) B 24) C 25) B 26) D 27) E 28) D Answers Heating Curves 29) E 30) A 31) 0.67 mol water 32) 1.06 g 33) 6.78 kj 34) D 35) B 36) D 37) C 38) D 39) B Enthalpy 40) B 41) D 42) B 43) A 44) C 45) C 46) C 47) A 48) B 49) B 50) A 51) D 52) C 53) D 54) C 55) B Hess Law 56) A 57) A 58) A 59) A 60) B 61) D 62) B 63) C 64) D Heats of Formation 65) D 66) A 67) E 68) A 69) D 70) A 71) E 72) E 73) C 74) B 75) D 76) A 77) D 78) C 79) E 80) A 81) C 82) D 83) C 84) C