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For which of the following substances does Δ H 0,f298 = 0?

Calculate standard enthalpy change, bond energies, average bond energy, heat of combustion, and entropy for various reactions and substances.

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For which of the following substances does Δ H 0,f298 = 0?

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  1. For which of the following substances does ΔH0,f298 = 0? • ZnO(s) • H2O(l) • Hg(l) • I2(l) • C(diamond)

  2. Calculate the standard enthalpy change at 25°C accompanying the reaction of 114 grams of sulfur trioxide with a stoichiometric quantity of water.                          SO3(g) + H2O(l) {image} H2SO4(l) ΔH0,f(kJ/mol)    -395.6      -285.8           -814.0 • -251 kJ • - 442 kJ • -189 kJ • -118 kJ • 1.17 x 103 kJ

  3. Calculate the enthalpy change for the following reaction using the given bond energies. C2H4(g) + H2O(g) {image} C2H5OH (g) C=C 602 kJ/mol C-H 413 kJ/mol O-H 463 kJ/mol C-O 358 kJ/mol C-C 346 kJ/mol • -550 kJ • -52 kJ • -654 kJ • 35 kJ • 361 kJ

  4. Given the following bond energies and standard enthalpy of formation for NF3(g): F-F 155 kJ/mol, {image} 945 kJ/mol 1/2 N2(g) + 3/2 F2(g) {image} NF3(g) ; ΔH0 = -103 kJ/mol Evaluate the average N-F bond energy in NF3(g). • 113 kJ/mol • 269 kJ/mol • 317 kJ/mol • 66 kJ/mol • 328 kJ/mol

  5. The temperature of the water and calorimeter changes from 25.023°C to 28.263°C, when 0.902 g of benzoic acid (C6H5COOH) is burned in a bomb calorimeter with excess oxygen. Calculate ΔE (in kJ/g) for this reaction. The value of the "calorimeter constant", the heat capacity of the calorimeter plus the water, is 7.706 kJ/°C. • -19.1 kJ/g • -27.7 kJ/g • -22.5 kJ/g • -15.6 kJ/g • -13.9 kJ/g

  6. Given the following data at 298 K, calculate ΔS0 for the given reaction. 2Ag2O(s) {image} 4Ag(s) + O2(g) {image} Ag(s) 42.55 ; Ag2O(s) 121.7 ; O2(g) 205.0 • 68.62 J/K • 131.8 J/K • 117.7 J/K • 93.76 J/K • 606.7 J/K

  7. Which of following would have the lowest value of absolute entropy per mole? • water at 50°C • steam at 100°C • ice at 0°C • superheated steam at 200°C • a salt-ice-water bath for freezing ice cream

  8. Based on the relationship of entropy to the degree of disorder in a system, which of the following changes are accompanied by an increase in entropy? I. The sublimation of iodine. II. The freezing of ethyl alcohol. III. The extraction of metals from their ores. IV. The burning of a solid rocket fuel. V. The thermal decomposition of ammonium nitrate. 2NH4NO3(s) {image} 2N2(g) + 4H2O(g) + O2(g) • II and III • I and IV • III, IV, and V • I, IV, and V • II, III, and V

  9. Estimate the boiling point of hydrogen peroxide, H2O2. For H2O2 (l), ΔH0,f = -187.8 kJ/mol and S0 = 109.6 J/mol·K. For H2O2 (g), ΔH0,f = -136.3 kJ/mol and S0= 233 J/mol·K. • 67.6°C • 145°C • 26.2°C • -11.4°C • 118°C

  10. For which set of values of ΔH and ΔS will a reaction be nonspontaneous (reactant-favored) at all temperatures? • ΔH = +10 kJ, ΔS = -5 J/K • ΔH = -10 kJ, ΔS = -5 J/K • ΔH = -10 kJ, ΔS = +5 J/K • ΔH = +10 kJ, ΔS = +5 J/K • no such values exist

  11. The ΔG at 298 K for the reaction below is +115 kJ/mol. Calculate S0 for Mn3O4(s). 3MnO2(s) {image} Mn3O4(s) + O2(g) ΔH0,f (kJ/mol)/ -520. / -1387 / 0 S0 (J/mol•K) / 53 / ? / 205 • 149 J/mol·K • 534 J/mol·K • 43 J/mol·K • 339 J/mol·K • 3440 J/mol·K

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