EXAM PRACTIVE QUESTIONS Chapter 15 1. The roasting of 48.7 g of ZnS at constant pressure liberates 220. kJ of heat. Calculate the 'H for this reaction. 2 ZnS(s) + 3 O2(g) o 2 ZnO(s) + 2 S O2(g) -440. kJ/mol rxn 2. From the following data at 25 qC, H2(g) + Cl2(g) o 2 HCl(g) 'Hq = -185 kJ 2 H2(g) + O2(g) o 2 H2O(g) 'Hq = -483.7 kJ Calculate 'Hq at 25 qC for the reaction below. 4 HCl(g) + O2(g) o 2 Cl2(g) + 2 H2O(g) -114 kJ 3. Given the enthalpy changes for the following reactions, calculate 'Hfq for CO(g). Hint: if CO is formed, it must be a product in the final reaction, which is not given, you must write it. C(graphite) + O2(g) o 2 CO2(g) 'Hq = -393.5 kJ CO(g) + ½ O2(g) o CO2(g) 'Hq = -283.0 kJ C(graphite) + ½ O2(g) o CO (g) 'Hq = -110.5 kJ 4. Calculate 'Hq at 25 qC for the reaction below. Fe3O4(s) + CO(g) o 3 FeO(s) + CO2(g) 'Hfq (kJ/mol) -1118 -110.5 -272 -393.5 19 kJ 5. How much heat is released or absorbed in the reaction of 10.0 g of SiO2 (quartz). SiO2(s) + 4 HF(aq) o SiF4(g) + 2 H2O(") 'Hfq (kJ/mol) -910.9 -320.8 -1615 -285.8 1.2 kJ 6. How much work is done when the following reaction occurs at constant pressure? N2(g) + O2(g) o 2 NO(g) 0 work 7. Calculate the average bond energy in kJ per mol of bonds for the C-H bond from the following data. C(graphite) + 2 H2(g) o CH4(g) 'Hrxnq = -74.81 kJ 'Hfq for H(g) = 218.0 kJ 'Hfq for C(g) = 716.7 kJ 415.9 kJ8. A system performs 390 L  atm of pressure-volume work (L  atm = 101.325 J) on its surroundings and it releases -9800 kJ of heat to its surroundings. What is the change in the internal energy. -9840 kJ 9. Assuming the gases are ideal, calculate the amount of work done (in J), for the conversion of 1.00 mole of CO(g) at 75 qC in the reaction below. The value of R is 8.314 J/molK. Ni (s) + 4CO(g) o 4 Ni(CO)4(g) 8680 J 10. Evaluate 'Sq for the reaction below at 25 qC and 1 atm. 3 NO2(g) + H2O(") o 2 HNO3(aq) + NO(g) Sq (J/molK) 240 69.91 146 210.7 -287.2 J/K 11. Calculate 'Gq at 298 K for the reaction below. N2O4(g) + 2 N2H4(") o 3 N2(g) + 4 H2O(g) 'Gfq (KJ/mol) 97.82 149.9 0 -228.6 -1311 kJ/mol 12. Evaluate 'Gq at 25 qC for the reaction below. P4O10(s) + 6 H2O(") o 4 H3PO4(s) 'Hfq (KJ/mol) -2984 -285.8 -1281 Sq (J/molK) 228.9 69.91 110.5 -363.7