Chapter 18, Problem 63E

Use standard free energies of formation to calculate $\Delta G°$ at 25°C for each reaction in Problem 61How do the values of $\Delta G°$ calculated this way compare to those calculated from $\Delta H°$ and $\Delta S°$ ? Which of the two methods could be used to determine how $\Delta G°$ changes with temperature?

61. For each reaction, calculate $\Delta H_{\text{rxn}}^{°}$ , $\Delta S_{\text{rxn}}^{°}$ and $\Delta G_{\text{rxn}}^{°}$ , and $\Delta G_{\text{rxn}}^{°}$ at 25°C and state whether the reaction is spontaneous. If the reaction is not spontaneous, would a change in temperature make it spontaneous? If so, should the temperature be raised or lowered from 25°C?

1. ${\text{N}}_2{\text{O}}_4(g)\to 2{\text{NO}}_2(g)$
2. ${\text{NH}}_4\text{Cl}(s)\to \text{HCl(}g)+{\text{NH}}_3(g)$
3. ${\text{3H}}_4(g)+{\text{Fe}}_2{\text{O}}_3(s)\to 2\text{Fe(}s)+3{\text{H}}_2\text{O}(g)$
4. ${\text{N}}_2(g)+3{\text{H}}_2(g)\to 2{\text{NH}}_3(g)$