CHAPTER HOMEWORK 6 KEY 24. Calculate the internal energy change for each of the following. a. One hundred (100.) joules of work are required to compress a gas. At the same time, the gas releases 23 J of heat.
b. A piston is compressed from a volume of 8.30 L to 2.80 L against a constant pressure of 1.90 atm. In the process, there is a heat gain by the system of 350. J.
c. A piston expands against 1.00 atm of pressure from 11.2 L to 29.1 L. In the process, 1037 J of heat is absorbed.
30. One mole of H2O (g) at 1.00 atm and 100. oC occupies a volume of 30.6 L. When one mole of H2O (g) is condensed to one mole of H2O (l) at 1.00 atm and 100. oC, 40.66 kJ of heat is released. If the density of H2O (l) at this temperature and pressure is 0.996 g/cm3, calculate E for the condensation of one mole of water at 1.00 atm and 100. oC.
36. Consider the following reaction: 2 H2 (g) + O2 (g) 2 H2O (l) H = -572 kJ a. How much heat is evolved for the production of 1.00 mol of H2O (l)?
b. How much heat is evolved when 4.03 g of hydrogen is reacted with excess oxygen?
c. How much heat is evolved when 186 g of oxygen is reacted with excess hydrogen?
d. The total volume of hydrogen gas needed to fill the Hindenburg was 2.0 x 108 L at 1.0 atm and 25 oC. How much heat was evolved when the Hindenburg exploded, assuming all of the hydrogen reacted?
42. The specific heat capacity of silver is 0.24 J/oC*g. a. Calculate the energy required to raise the temperature of 150.0 g Ag from 273 K to 298 K.
b. Calculate the energy required to raise the temperature of 1.0 mol Ag by 1.0 oC (called the molar heat capacity of silver).
c. It takes 1.25 kJ of energy to heat a sample of pure silver from 12.0 oC to 15.2 oC. Calculate the mass of the sample of silver.
52. In a coffee-up calorimeter, 1.60 g NH4NO3 is mixed with 75.0 g of water at an initial temperature of 25.00 oC. After dissolution of the salt, the final temperature of the calorimeter contents is 23.34 oC. Assuming solution the has a heat capacity of 4.18 J/oC*g and assuming no heat loss to the calorimeter, calculate the enthalpy change for the dissolution of NH4NO3 in units of kJ/mol.
64. Given the following data P4 (s) + 6 Cl2 (g) 4 PCl3 (g) P4 (s) + 5 O2 (g) P4O10 (s) PCl3 (g) + Cl2 (g) PCl5 (g) PCl3 (g) + 1/2 O2 (g) Cl3PO (g) calculate H for the reaction: P4O10 (s) + 6 PCl5 (g) 10 Cl3PO (g) H = -1225.6 kJ H = -2967.3 kJ H = -84.2 kJ H = -285.7 kJ
74. The standard enthalpy of combustion of ethene gas, C2H4 (g), is -1411.1 kJ/mol at 298 K. Given the following enthalpies of formation, calculate Hfo for C2H4 (g). CO2 (g) -393.5 kJ/mol H2O (l) -285.8 kJ/mol
84. Calculate Ho for the reaction: 2 K (s) + 2 H2O (l) 2 KOH (aq) + H2 (g) A 5.00 g chunk of potassium is dropped into 1.00 kg water at 24.0 oC. What is the final temperature of the water after the preceding reaction occurs? Assume that all the heat is used to raise the temperature of the water. (Never run this reaction. It is very dangerous; it bursts into flame!)
90. Given the following data: Fe2O3 (s) + 3 CO (g) 2 Fe (s) + 3 CO2 (g) 3 Fe2O3 (s) + CO (g) 2 Fe3O4 (s) + CO2 (g) Fe3O4 (s) + CO (g) 3 FeO (s) + CO2 (g) calculate Ho for the reaction FeO (s) + CO (g) Fe (s) + CO2 (g) Ho = -23 kJ Ho = -39 kJ Ho = +18 kJ
104. Nitromethane, CH3NO2, can be used as a fuel. When the liquid is burned, the (unbalanced) reaction is mainly: CH3NO2 (l) + O2 (g) CO2 (g) + N2 (g) + H2O (g) a. The standard enthalpy change of the reaction (Horxn) for the balanced reaction (with lowest whole-number coefficients) is -1288.5 kJ. Calculate the Hof for nitromethane.
b. A 15.0 L flask containing a sample of nitromethane is filled with O2 and the flask is heated to 100. oC. At this temperature, and after the reaction is complete, the total pressure of all gases inside the flask is 950. torr. If the mole fraction of nitrogen (nitrogen) is 0.134 after the reaction is complete, what mass of nitrogen was produced?