Embedded Files
Entropy and Gibbs Free Energy
1. 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)
a. Is ΔS positive or negative in these processes?
b. In which of the processes will the magnitude of the entropy change be greater?
2. Write the balanced chemical equation for the combustion of benzene, C6H6(l), to give carbon dioxide and water vapor. Would you expect ΔS to be positive or negative in this process?
3. Calculate ΔS∘298 for the following changes.
a. SnCl4(l)⟶SnCl4(g)
b. CS2(g)⟶CS2(l)
4. Use the standard free energy of formation data in Appendix G to determine the free energy change for each of the following reactions, which are run under standard state conditions and 25 °C. Identify each as either spontaneous or nonspontaneous at these conditions.
a. MnO2(s)⟶Mn(s)+O2(g)
b. H2(g)+Br2(l)⟶2HBr(g)
c. Cu(s)+S(g)⟶CuS(s)
5. Consider the decomposition of red mercury(II) oxide under standard state conditions.
2HgO(s,red)⟶2Hg(l)+O2(g)
a. Is the decomposition spontaneous under standard state conditions?
b. Above what temperature does the reaction become spontaneous?
6. Calculate ΔG° for each of the following reactions from the equilibrium constant at the temperature given.
a. N2(g)+O2(g)⟶2NO(g)T=2000°C Kp=4.1×10^-4
b. H2(g)+I2(g)⟶2HI(g)T=400°C Kp=50.0
c. CO2(g)+H2(g)⟶CO(g)+H2O(g)T=980°C Kp=1.67
7. Calculate the equilibrium constant at the temperature given.
a. (a) O2(g)+2F2(g)⟶2F2O(g)(T=100°C)
b. I2(s)+Br2(l)⟶2IBr(g)(T=0.0°C)
8. Under what conditions is N2O3(g)⟶NO(g)+NO2(g) spontaneous?
9. The evaporation of one mole of water at 298 K has a standard free energy change of 8.58 kJ.
H2O(l)⇌H2O(g) ΔG∘298=8.58kJ
a. Is the evaporation of water under standard thermodynamic conditions spontaneous?
b. Determine the equilibrium constant, KP, for this physical process.
Google Sites
Report abuse