R = 8.314 ´ 10–3 kJ·mol–1·K–1

F = 96485 C·mol–1


DS = qrev/T

(at const. T)

q = DH

(at const. P)

DGr° = DHr° - TDSr°      

DSr° = S n Sm°(prod) – S n Sm°(react)

DHr° = S n DHf°(prod) – S n DHf°(react)

DGr° = – RT lnK

DGr = DGr° + RT lnQ

E° = (0.0257/n) lnK

(at 298 K)

E = E° – (0.0257/n) lnQ

(at 298 K)

DGr° = – nFEcell°   n = (I t)/F   
For E° values use the attached table.






1. All of the following changes give a positive DSr° except
A.N2(g) + 3H2(g) ® 2NH3(g)
B.Na(l) ® Na(g)
C.H2O(s) ® H2O(l)
D.H2O(l) ® H2O(g)
E.H2O(l, 20°C) ® H2O(l, 50°C)


2. If the enthalpy of vaporization of water at 100°C is 40.7 kJ·mol–1, calculate DS° for vaporization of one mole of H2O(l) at 100°C.
A.109 J·K–1
B.136 J·K–1
C.–40.7 ´ 103 J·K–1
D.40.7 ´ 103 J·K–1
E.–109 J·K–1


3. Consider the following reaction.
   CaCO3(s) ® CaO(s) + CO2(g)
If this reaction is endothermic, which one of the following statements is true at 1 atm?
A.DHr° is negative.
B.DGr° is negative at low temperatures.
C.DGr° is positive at all temperatures.
D.DSr° is negative.
E.DGr° is negative at high temperatures.


4.

Calculate DGr° for the decomposition of ammonium nitrate at 298 K.


NH4NO3(s)

®

N2O(g)

+

2H2O(l)

DHf°, kJ·mol-1

-365.56

82.05

-285.83

Sm°, J·K-1·mol-1

151.08

219.85

69.91


A.+120.45 kJ
B.-332.64 kJ
C.+99.62 kJ
D.-186.21 kJ
E.-124.05 kJ


5. For the following reaction
   C6H6(g) + 3H2(g) ® C6H12(g)
at 298 K, DHr° = -206 kJ and DSr° = -363 J·K-1. Calculate DGr° at 500°C.
A.-487 kJ
B.-157 kJ
C.+75 kJ
D.-97 kJ
E.-245 kJ


6. Consider the following reaction
   NO(g) + 1/2 O2(g) b NO2(g)
If DHr° = -56.52 kJ and DSr° = -72.60 J·K-1 at 298 K, calculate the equilibrium constant for the reaction at 298 K.
A.7.63 ´ 10-7
B.1.30 ´ 106
C.1.22 ´ 1014
D.660
E.8.08 ´ 109


7. If Kp for the reaction
   N2O4(g) b 2NO2(g)
is 0.15 at 25°C, calculate DGr° for this reaction.
A.2.0 kJ
B.4.7 kJ
C.-0.4 kJ
D.-4.7 kJ
E.-2.0 kJ


8. Calculate DGr for the following reaction at 298 K.
   Ag(NH3)2+(aq, 0.100 M) b Ag+(aq, 0.00100 M) + 2NH3(aq, 0.00200 M)
DGr° = -41.0 kJ for this reaction at 298 K.
A.-42.2 kJ
B.14.2 kJ
C.-83.2 kJ
D.83.2 kJ
E.-1.2 kJ


9.

Estimate the temperature at which oxygen reacts with Hg(l).


2Hg(l)

+

O2(g)

®

2HgO(s)

DHf°, kJ·mol-1

-90.83

Sm°, J·K-1·mol-1

76.02

205.14

70.29


A.above 255 K
B.at 295 K
C.at 760 K
D.below 839 K
E.above 709 K


10. Given: Cr2O72–(aq) ® Cr3+(aq) in acidic solution.
When this half-reaction is balanced, the coefficient of H+ is
A.14
B.8
C.10
D.12
E.4


11. When the reaction below is balanced in acidic solution, the coefficient of S(s) is
   MnO4- + S2- ® S(s) + MnO2(s)
A.1
B.2
C.3
D.4
E.5


12. Write the cell diagram for the reaction
   Cl2(g) + 2Br-(aq) ® 2Cl-(aq) + Br2(l)
A.Pt½Br2(l)½Br-(aq)mCl-(aq)½Cl2(g)½Pt
B.Pt½Cl2(g)½Br-(aq)mCl-(aq)½Br2(l)½Pt
C.Pt½Cl2(g)½Cl-(aq)mBr-(aq)½Br2(l)½Pt
D.Pt½Cl-(aq),Br-(aq)mBr2(l)½Cl2(g)½Pt
E.Pt½Br2(l)½Cl2(g)mCl-(aq)½Br-(aq)½Pt


13. Which species will oxidize V2+ but not Br–?
A.Fe3+
B.F2
C.Mn2+
D.Cr3+
E.Zn2+


14. If the standard potentials for the couples Cu2+/Cu, Ag+/Ag, and Fe2+/Fe are +0.34,
+ 0.80, and –0.44 V, respectively, which is the strongest reducing agent?
A.Fe
B.Ag+
C.Fe2+
D.Cu
E.Ag


15. Which of the following is the strongest oxidizing agent?
A.Ca2+
B.Cu2+
C.Co2+
D.Cr3+
E.Fe2+


16. The standard potential of the cell
   Ag(s)½Ag+(aq)mCl-(aq)½AgCl(s)½Ag(s)
is -0.58 V at 25°C. Calculate the equilibrium constant for the cell reaction.
A.1.2 ´ 10-5
B.2.7 ´ 10-23
C.1.6 ´ 10-10
D.5.7 ´ 10-18
E.6.3 ´ 109


17. Given: 2Cu+(aq) ® Cu(s) + Cu2+(aq)
If Ecell° for this reaction is 0.18 V at 25°C, calculate DGr°.
A.–95 kJ
B.–35 kJ
C.+17 kJ
D.+35 kJ
E.–17 kJ


18. How many moles of Cl2(g) are produced by the electrolysis of concentrated NaCl(aq), if 2.00 A are passed through the solution for 8.00 hours?
A.0.894 mol
B.0.149 mol
C.0.298 mol
D.0.596 mol
E.0.00496 mol


19. Calculate E for the half-reaction below.
   2H+(aq, 1.00 ´ 10–7 M) + 2e– ® H2(g, 1.00 atm)
A.0 V
B.+0.414 V
C.–0.829 V
D.+0.829 V
E.–0.414 V


20. The products of the electrolysis of CuF2(aq) with inert electrodes are
A.H2(g) and F2(g).
B.Cu(s) and H2(g).
C.H2(g) and O2(g).
D.Cu(s) and F2(g).
E.Cu(s), O2(g), and H+(aq).



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