Gen. Chem.- Chap. 17
Choose the correct answer for each question.
 

1Which of the following reactions are accompanied by an INCREASE in entropy?
2 SO3 (g) + O2 (g) -----> SO3 (g)
H2O (l) -----> H2O (s)
N2O4 (g) ----> 2 NO2 (g)
both b and c

2Calcuate dS for the following reaction N2H4 (l) ----> N2 (g) + 2 H2 (g)
given... S (N2H4 (l)) = +121.2 J/mol-K, S (N2 (g)) = +191.5 J/mol-K, S (H2 (g)) = +130.6 J/mol-K
+331.5 J/K
-331.5 J/K
+200.9 J/K
+443.3 J/K

3For a spontaneous process, which of the following is always positive?
dG
dSuniv
enthalpy
dSsys

4A positive sign for dG indicates...
a low activation energy
an endothermic reaction
dS must be negative at standard conditions
a nonspontaneous reaction at standard conditions

5For a given reaction, if the sign of dH is - and the sign of dS is -, the reaction will be...
spontaneous at all T
non-spontaneous at all T
spont. at hi T, non-spont. at lo T
spont. at lo T, non-spont. at hi T

6 Calculate dG for the following reaction at 25C. Is this reaction spontaneous or nonspontaneous at 25C?
4 Fe (s) + 3 O2 (g) ----> 2 Fe2O3 (s)
given... dH = -1648.4 kJ and dS = -549.4 J/K
+1432 kJ, spontaneous
-1485 kJ , spontaneous
-1812 kJ, spontaneous
+345.7 kJ, nonspontaneous

7Given the reaction and data above, at what temperature does this reaction become spontaneous?
it is never spontaneous
it is always spontaneous
spontaneous at temperatures below 3000K
spontaneous at temperatures above 20.4K

8Calculate dG for the following equation
Mg (s) + 2 H2O (l) ----> Mg(OH)2 (s) + H2 (g) given...
dGf(H2O) = -237.2 kJ/mol, dGf (Mg(OH)2 (s)) = -833.6 kJ/mol
-359.2 kJ
-596.4 kJ
+596.4 kJ
-1308 kJ

9Given the following equation, calculate K at 25C. (R= 0.00821 kJ/mol-K)
CO (g) + H2O (g) -----> CO2 (g) + H2 (g) dG= -28.5 kJ
4.5 x 103
3.2 x 10-4
2.9 x 106
1.0 x 105

10 For the following reaction...
2 PbS (s) + 3 O2 (g) ----> 2 PbO (s) + 2 SO2 (g) dG = -780.7 kJ at 25C. Calculate dG for the reaction at 25C if the P O2 = 3.0 atm and the P SO2 = 2 atm. (R = 0.00821 kJ/mol-K)
-781.7 kJ
+12.4 kJ
-785.4 kJ
+148.1 kJ