Question 18: ->> C (s). This reaction: Consider the endothermic reaction A (s) + B (g) --- Is spontaneous at low temperatures Is spontaneous at high temperatures Is nonspontaneous at all temperatures Is spontaneous at all temperatures Check Reuse <> Embed H-P

Many plastic materials are organic polymers that contain carbon and hydrogen. The oxidation of these plastics in air to farm carbon dioxide and water is a spontaneous process; however, plastic materials tend to persist in the environment. Explain.

If you calculate a value for G for a reaction using the values of Gf in Appendix 4 and get a negative number, is it correct to say that the reaction is always spontaneous? Why or why not? Free energy changes also depend on concentration. For gases, how is G related to the pressure of the gas? What are standard pressures for gases and standard concentrations for solutes? How do you calculate G for a reaction at nonstandard conditions? The equation to determine G at nonstandard conditions has Q in it: What is Q? A reaction is spontaneous as long as G is negative; that is, reactions always proceed as long as the products have a lower free energy than the reactants. What is so special about equilibrium? Why dont reactions move away from equilibrium?

Estimate the temperature range over which each of the following reactions is spontaneous. (a) 2Al(s)+3Cl2(g)2AlCl3(s) (b) 2NOCl(g)2NO(g)+Cl2(g) (c) 4NO(g)+6H2O(g)4NH3(g)+5O2(g) (d) 2PH3(g)3H2(g)+2P(g)

What is a spontaneous reaction?

A reaction has H298=100 kj/mol and S298=250 J/mol K. Is the reaction spontaneous at room temperature? If not, under what temperature conditions will it become spontaneous?

What types of experiments can be carried out to determine whether a reaction is spontaneous? Does spontaneity have any relationship to the final equilibrium position of a reaction? Explain.

The free energy change for a reaction, G, is an extensive property. What is an extensive property? Surprisingly, one can calculate G from the cell potential. , for the reaction. This is surprising because : is an intensive property. How can the extensive property G be calculated from the intensive property ?

Given that H f for HF(aq) is -320.1 kJ/mol and S for HF(aq) is 88.7 J/mol K, find Ka for HF at 25C.

Consider two processes: sublimation of I2(s) and melting of I2(s) (Note: the latter process can occur at the same temperature but somewhat higher pressure). I2(s)I2(g)I2(s)I2(l) Is S positive or negative in these processes? In which of the processes will the magnitude of the entropy change be greater?