1. Calculate the standard free energy change at 500 K for the following reaction.
Cu_{(s)} + H_{2}O_{(g)} à CuO_{(s)} + H_{2(g)}
ΔH˚_{f} (kJ/mol) 
S˚ (J/mol·K) 

Cu_{(s)} 
0 
33.3 
H_{2}O_{(g)} 
241.8 
188.7 
CuO_{(s)} 
155.2 
43.5 
H_{2(g)} 
0 
130.6 
2. When solid ammonium nitrate dissolves in water, the resulting solution becomes cold. Which is true and why?
a. ΔH˚ is positive and ΔS˚ is positive
b. ΔH˚ is positive and ΔS˚ is negative
c. ΔH˚ is negative and ΔS˚ is positive
d. ΔH˚ is negative and ΔS˚ is negative
e. ΔG is negative independent of temperature
3. For a reaction, the value of the equilibrium constant, K, at 298 K is 5.0 x 10^{8}. The standard free energy change for this reaction is what?
4. Given the reaction P_{2(g)} + 3Cl_{2(g) } > 2PCl_{3(g)} the standard free energy change is 642.9 kJ at 298 K. If the partial pressure of phosphorus (P_{2}) gas is 1.5 atm, chlorine gas is 1.6 atm, and phosphorus trichoride gas 0.65 atm, calculate the free energy change for the reaction.
deltaG= deltaHTdeltaS
deltaG for Cu(s) = 0 500k(0.0333kJ/molK) = 16.65kJ/mol (keeping the given values of delta H,T,deltaS)
deltaG for H2O(g) = 241.8kJ/mol  500k*(0.1887J/molK) = 94.59kJ/mol
deltaG for CuO(s) = 155.2kJ/mol 500k*(0.0435kJ/molK) = 176.95kJ/mol
deltaG for H2(g) = 0  500K*(0.1306kJ/molK) = 65.3kJ/mol
DeltaGrxn = sum of deltaG for products  sum of deltaG for reactants
= (176.5+(65.3))  (16.65+(94.59))
= 241.8  (111.24) = 130.56kJ/mol
deltaG rxn = 130.56kJ/mol
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