Chapter 14, Problem 63P

What is the sign of the standard Gibbs free-energy change at low temperatures and at high temperatures for the synthesis of ammonia? 3H2(g) + N2(g) 2NH3(g)

Calculate the standard Gibbs free-energy change when SO3 forms from SO2 and O2 at 298 K. Why is sulfur trioxide an important substance to study? (Hint: What happens when it combines with water?)

Consider the reaction of 2 mol H2(g) at 25C and 1 atm with 1 mol O2(g) at the same temperature and pressure to produce liquid water at these conditions. If this reaction is run in a controlled way to generate work, what is the maximum useful work that can be obtained? How much entropy is produced in this case?

Which contains greater entropy, a quantity of frozen benzene or the same quantity of liquid benzene at the same temperature? Explain in terms of the dispersal of energy in the substance.

Elemental boron, in the form of thin fibers, can be made by reducing a boron halide with H2. BCl3(g) + 3/2 H2(g) B(s) + 3HCl(g) Calculate H, S, and G at 25 C for this reaction. Is the reaction predicted to be product favored at equilibrium at 25 C? If so, is it enthalpy driven or entropy driven?

Consider the reaction of 1 mol H2(g) at 25C and 1 atm with 1 mol Br2(l) at the same temperature and pressure to produce gaseous HBr at these conditions. If this reaction is run in a controlled way to generate work, what is the maximum useful work that can be obtained? How much entropy is produced in this case?

Silver carbonate, Ag2CO3, is a light yellow compound that decomposes when heated to give silver oxide and carbon dioxide: Ag2CO3(s)Ag2O(s)+CO2(g) A researcher measured the partial pressure of carbon dioxide over a sample of silver carbonate at 220C and found that it was 1.37 atm. Calculate the partial pressure of carbon dioxide at 25C. The standard enthalpies of formation of silver carbonate and silver oxide at 25C are 505.9 kJ/mol and 31.05 kJ/mol, respectively. Make any reasonable assumptions in your calculations. State the assumptions that you make, and note why you think they are reasonable.

Benzene can be prepared from acetylene. 3C2H2(g)C6H6(g). Determine the equilibrium constant at 25 C and at 850 C. Is the reaction spontaneous at either of these temperatures? Why is all acetylene not found as benzene?

The standard free energies of formation and the standard enthalpies of formation at 298 K for difluoroacetylene (C2F2) and hexafluorobenzene (C6F6) are Gfo(KJ/mol) Hfo(KJ/mol) C2F2(g) 191.2 241.3 Hexane 78.2 132.8 For the following reaction: C6F6(g)3C2F2(g) a. calculate S at 298 K. b. calculate K at 298 K. c. estimate K at 3000. K, assuming H and S do not depend on temperature.