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1.  Answer Question 7 on the 1997 AP examination. (An example of an AP essay question.) 

2.  Answer Question 3 on the 1996 AP examination. (An example of an AP  free response problem.) 
 
3.  i.  In which of the following changes at constant pressure is work done by the surroundings on the system? By the system on the surroundings? Is essentially no work done? 
    ii.  What is the value of w in each case: w > 0, w < 0, or w = 0 or almost 0? 
 
 

Initial State Final State
a. H2O(g)  H2O(l)
b. H2O(s) H2O(g)
c.  2Na(s) + Cl2(g)  2NaCl(s)
d. H2(g) + Cl2(g) 2HCl(g)
e. Na2SO4.10H2O(s) Na2SO4(s) + 10H2O(g)
f. NO2(g) + CO(g) NO(g) + CO2(g)
4.  Does the entropy of each of the following systems at standard state conditions increase, decrease, or not change in going from the initial to the final state? If the entropy does change, give the sign of DeltaS and explain your answers. 
 
Initial State Final State
a.
NaCl(s) at 298 K
NaCl(s) at 0 K
b.
H2O(s) at 273 K and 1 atm
H2O(l) at 273 K and 1 atm
c.
1 mol Si and 1 mol O2
1 mol SiO2
d.
1 mol CaCO3
1 mol CaO and 1 mol CO2
 
5.  As ammonium nitrate dissolves spontaneously in water at constant pressure the solution gets cold. What is the sign of DeltaH for this process? Is it possible to identify the sign of the entropy change for the process from this information? Explain your answer. 

6.  As sulfuric acid dissolves spontaneously in water at constant pressure, heat is produced and the solution gets hot. What is the sign of the enthalpy change for this process? Is it possible to identify the sign of DeltaS for the process from this information? Explain your answer. 

7.  A system with a negative DeltaG will undergo reaction spontaneously. When the system reaches equilibrium for that reaction, the reaction is no longer spontaneous. Explain the changes in the system that shift the reaction from spontaneous to nonspontaneous. 

8.  i.  Predict whether the entropy of each of the following systems should increase, decrease, or remain approximately constant during the following reactions. If the entropy does change, give the sign of Delta S. 

(a) MnO2(s)  Mn(s) + O2(g) 
(b) H2(g) + Br2(l)  2HBr(g) 
(c) Cu(s) + S(g)  CuS(s) 
(d) 2LiOH(s) + CO2(g)  Li2CO3(s) + H2O(g) 
(e) CH4(g) + O2(g)  C(s) + 2H2O(g) 
(f) CS2(g) + 3Cl2(g)  CCl4(g) + S2Cl2(g) 
   ii.  Which of the reactions in this question exhibit an entropy change that favors a spontaneous reaction under standard state conditions? 

9.  i.   Use standard free energy data to determine the free energy change for each of the following reactions, which are run under standard state conditions. 

(a) MnO2(s)  Mn(s) + O2(g) 
(b) H2(g) + Br2(l)  2HBr(g) 
(c) 2LiOH(s) + CO2(g)  Li2CO3(s) + H2O(g) 
(d) SnCl4(l)  SnCl4(g) 
    ii.   For which of the reactions in this question does the free energy change indicate a spontaneous reaction under standard state conditions? 

10.   The standard molar enthalpies of formation of NO(g), NO2(g), and N2O3(g) are 90.25 kJ mol -1, 33.2 kJ mol -1, and 83.72 kJ mol -1, respectively. Their standard molar entropies are 210.65 J mol -1 K-1, 239.9 J mol -1 K-1, and 312.2 J mol -1 K-1, respectively. 

(a) Use these data to calculate the free energy change for the following reaction at 25.0oC. 

N2O3(g)  NO(g) + NO2(g) 

(b) Repeat the above calculation for 0.00o C and 100.0oC, assuming that the enthalpy and entropy changes do not vary with a change in temperature. Is the reaction spontaneous at 0.00oC? At 100.0oC?

11. Calculate DeltaGo for the following reaction from the equilibrium constant at the temperature given. 
H2(g) + I2(g)  2HI(g)         T = 400oC         KP = 50.0 
12. Calculate the equilibrium constant (the vapor pressure) at 25o C for the following reaction from the value of Delta Go298. 
SnCl4(l)  SnCl4(g) DeltaGo298 = 8.0 kJ 
 
13. Calculate the equilibrium constant for the following reaction at the temperature given. 
2LiOH(s) + CO2(g)  Li2CO3(s) + H2O(g)            T = 575oC 
What are the assumptions made in this calculation?  
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