5. For a particular chemical reaction AH = 5.5 kJ and AS = -25 J/K. Under what temperature condition is the reaction spontaneous? a. When T < -220 K. b. When T< 220 K. c. The reaction is spontaneous at all temperatures. d. The reaction is not spontaneous at any temperature. e. When T > 220 K.

For the reaction NO(g)+NO2(g)N2O3(g) , use tabulated thermodynamic data to calculate H and S. Then use those values to answer the following questions. (a) Is this reaction spontaneous at 25°C? Explain your answer. (b) If the reaction is not spontaneous at 25°C, will it become spontaneous at higher temperatures or lower temperatures? (c) To show that your prediction is accurate, choose a temperature that corresponds to your prediction in part (b) and calculate G . (Assume that both enthalpy and entropy are independent of temperature.)

How does the second law of thermodynamics explain a spontaneous change in a system that becomes more ordered when that process is exothermic?

Thermite reactions have been used for welding metal parts such as railway rails and in metal refining. One such thermite reaction is Fe2O3(s)+2Al(s)Al2O3(s)+2Fe(s). Is the reaction spontaneous at room temperature under standard conditions? During the reaction, the surroundings absorb 851.8 kJ/mol of heat.