Thermo Review
Thermo Review 1. What is the E (in J) of a system that releases 12.4 J of heat and does 4.2 J of work on the surroundings. 2. Which of the following conditions would always result in an increase in E of a system? A) B) C) D) E) 3. A A) B) C) D) E) The system loses heat and does work on the surroundings. The system gains heat and does work on the surroundings. The system loses heat and has work done on it by the surroundings. The system gains heat and has work done on it by the surroundings. None of these is correct. H corresponds to an process. Negative, endothermic Negative, exothermic Positive, exothermic Zero, exothermic Zero, endothermic 4. Which of the following statements is not true regarding enthalpy? a) b) c) d) e) The change in enthalpy is positive for a process that absorbs heat. Enthalpy is a state function. Enthalpy is an extensive property. A change in enthalpy is measured at a constant pressure. The enthalpy of a system can be measured. 5. For the hypothetical reaction 3X2 (g) 2X3 (g), H is –333 kJ (the atomic weight of X is 66.6 amu). H for conversion of 11.1g of X3 a gas into X2 gas is kJ. 6. The value of H for a reaction below is 336kJ. Determine the amount of heat ( in kJ) exchanged wit the surroundings when 23.0 g of HCl is formed. CH4 (g) + 3Cl2 (g) CHCl3 (l) + 3HCl (g) 7. The value of H for the reaction below is –6535kJ. How many kJ of heat are evolved in the combustion of 16.0g of C6H6 (l)? 2C6H6 (l) +15O2 (g) 12CO2 (g) +6 H2O (l) 8. When a sample of aluminum is absorbed 9.86J of heat, its temperature increased from 23.2 C to 30.5 C. Since the specific heat of aluminum is .90 J/g-K, the mass of the sample was g. 9. When 29 J of heat is transferred to 15g of lead at 22 C, the temperature of the lead increases to 37 C. What is the specific heat capacity (J/g-k) of lead? 10. A 1.96 g sample of titanium was burned in a bomb calorimeter that had a heat capacity of 9.84 kJ/k. The temperature of the calorimeter increased from 36.84C to98.82C. Calculate the heat (kJ) that is released from the combustion of one mole of titanium. 11. Consider the following thermochemical equations: Fe2O3 + 3CO 2Fe + 3CO2 H = -28.0 kJ 3Fe + 4CO2 4CO + Fe3O4 H = +12.5 kJ Calculate the value of H (in kJ) for: 3Fe2O3 + CO CO2 + 2Fe3O4 12. Calculate H (in kJ/mol) for: Ca(OH)2 + 2H3AsO4 Ca(H2AsO4)2 + H2O Substance Hf (kJ/mol) Ca(OH)2 H3AsO4 Ca(H2AsO4)2 H2O -986.6 -900.4 -2346.0 -258.9 13. The thermodynamic quanity that expresses the degree of disorder in a system is ___________. a) enthalpy b) internal energy c) bond energy d) entropy e) heat flow 14. The entropy of the universe is _____________. a) constant b) continually decreasing c) continually increasing d) zero e) isotonic 15. Given the following table of thermodynamic data, Substance ΔHf° S° PCl3 (g) -288.07 kJ/mol 311.7 J/mol-K PCl3 (l) -319.6 217 Determine the normal boiling point (in °C) of PCl3 16. ΔS° will be positive for the reaction ____________. a) 2H2 (g) + O2 (g) 2H2O (g) b) 2NO2 (g) N2O4 (g) c) H+ (aq) + F- (aq) HF (aq) d) BaF2 (s) Ba2+ (aq) + 2F- (aq) e) 2Hg (l) + O2 (g) 2HgO (s) 17. Calculate ΔS° for the reaction below at 25°C. 4Al (s) + 3O2 (g) 2Al2O3 (s) Substance Al(s) Al2O3 (s) O2 (g) ΔS° (J/mol · K) 28.32 51.0 205.0 18. Consider the following reaction at 25°C. C(s) + H2O(g) CO(g) + H2(g) ΔG° = 91.2 kJ ΔH° = 131.4 kJ What is the value of ΔS° (J/K) for this reaction at 25°C. 19. Determine the value of ΔG° (kJ) for the following reaction using data from the table below. 2H20(g) + O2(g) 2H2O2 (g) Substance ΔG°f (kJ/mol) 2H20 -228 H2O2 -105 20. For the Reaction C2H6(g) C2H4(g) + H2 (g) ΔH is 137 kJ and ΔS° is 120 J/K. This reaction will be a) spontaneous at all temperatures b) spontaneous only at high tempratures c) spontaneous only at low tempratures d) nonspontaneous at all tempratures e) unreliable 21. for a reaction to be spontaneous at all tempratures, the signs of ΔH° and ΔS° must be ___________ and ___________, respectively. a) +, + b) +, c) -,+ d) -, e) +, 0
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