CHEM 1212 New Sample TEST #4 Questions
04/27/2015
Name__________________
KSU (Dr. Kim, T4C1212NS_15S )
1mi=1.609km; 1lbs=453.6g; 1gal=3.785L; 1in=2.54cm, 1mL=1cm3; c=2.9979x108m/s;
d(H2O)=1.00g/mL; s(H2O)=4.184J/oC.g; g=9.807m/s2;
1atm=760mmHg=14.7psi=101,325Pa; d(Hg)=13.60g/mL ;
R=0.08206L.atm/(K.mol)=8.315J/(K.mol) =1.987 cal/(K.mol); 1cal=4.184J; 1BTU=252cal;
1L.atm=101.3J; Faraday=96500Coulombs; 1atm==101,325Pa;
1e-=-1.602x10-19Coulomb; h=6.626x10-34J.s; me=9.109x10-31kg, 1 Therm=105 MJ;
1BTU=252cal; 1L.atm=101.3J.
Show your work for the underlined questions on the test.
Chemical Thermodynamics
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1. Which unit is not for an energy?
A(1 cal), B(1 J), C(1 kWh), D(1 kg/(ms2)), E(1kg.m2/s2), F(1L.Atm).
2. Which of above is the largest quantity of energy?
3. Internal Energy (E) of a system is a sum of kinetic energy and potential energy of all particles
in it. a(True),b(False). It is an c(intensive), d(extensive) property. A(a,c), B(a,d), C(b,c), D(b,d).
4. A gas expanded from 1.0 L to 5.0 L at 1.0 atm and at a constant temperature. Calculate the
work (w).
A(-0.41), B(-0.21), C(+0.21), D(+0.41) kJ.
5. The gas above also absorbed 672 J of heat from the surrounding.
Find the internal energy change(ΔE). A(-1,080), B(+1,080), C(-260), D(+260) J.
6. Enthalpy (H) is defined as a(E + PV), b(E - PV);
for an exothermic reaction , c(ΔH< 0), d(ΔH > 0). A(a,c), B(a,d), C(b,c), D(b,d).
7. Gibbs Free Energy is (G) is defined as a(H + TS), b(H - TS) at a constant pressure;
for an exothermic reaction , c(ΔG< 0), d(ΔG > 0). A(a,c), B(a,d), C(b,c), D(b,d).
8. Which one has a standard free energy of formation (Gfo) value of a zero?
A(H+(g)), B(H(g)), C(H2(g)), D(H2(s)), E(H2O(l)).
9. Boltzmann formulated that an entropy, a measure of disorder of a system, is (a) directly,
(b) inversely proportional to the (c) logarithm, (d) first power of a number of possible
microstates.
A(a,c), B(a,d), C(b,c), D(b,d).
10. Which one is an entropy increasing reaction ? A(2H2(g)+ O2(g)  2H2O (g)),
B(NH4Cl(s)  NH3 (g)+HCl (g)), C(I2(s)  I2(g)), D(2Zn(s)+ O2(g)  2ZnO(s)), E(B and C).
11. The standard entropy value(So) of water vapor (H2O(g)) is 188.7 J/(mol.K). So of liquid water
(H2O(l)) must be A(0.0), B(69.9), C(188.7), D(238.8) J/(mol.K).
12. Which reaction is referred to when a standard enthalpy (or free energy) of formation,
Hfo = -410.9 kJ/mol (or Gfo = -384.0 kJ/mol , of NaCl(s) is spoken ?
A (Na+(aq) + Cl-(aq) → NaCl(s)),
B (Na(l) + ½Cl2(l) → NaCl(s) )
C (Na(s) + Cl(g) → NaCl(s)),
D (Na(s) + ½Cl2(g)) → NaCl(s))
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Given the combustion reaction of propane gas: C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(g)
ΔHof are -103.8, 0.0, -393.5, & -241.8kJ/mol for C3H8(g), O2(g), CO2(g), & H2O(g), respectively.
The standard entropies, So, are 269.91, 205.0, 213.7, & 188.7J/(K.mol) in that order.
13. Find ΔHo for the combustion. A(2,044), B(533), C(-533), D(-2,044) kJ/mol of C3H8.
14. Find ΔSo for the reaction is A(-72), B(72), C(-101), D(101) J/(K.mol).
15. Find ΔGo from ΔHo & ΔSo at 25oC. A(-2,074), B(-2,014), C(2,014), D(2,074) kJ/mol.
16. Equilibrium constant(K) for the reaction at 25oC is ca. A(1036), B(1098), C(10198), D(10364).
17. The combustion can be spontaneous at (A) Lower, (B) Higher, (C) All, (D) No temperatures.
18. Find the standard free energy for a decomposition of water: 2H2O(l)  2H2(g) + O2(g)
given ΔGof for a liquid water, -237kJ/mol. A(-474), B(-237), C(237), D(474) kJ.
19. Given ΔHo, 178kJ/mol, and ΔSo, +160J/K.mol, for CaCO3(s)  CaO(s) + CO2(g),
Find ΔGo (at 25oC). A(-475), B(-382.2), C(174), D(130) kJ/mol.
20. Select one.
[A] At what temperature (oC), ΔGo above can be negative so that the limestone decomposes
spontaneously to produce quick lime. A (-85), B(-35), C(386), D(835) oC.
[B] The molar heat of fusion of benzene is 10.9 kJ/mol. Calculate entropy change when one mol of
benzene melts at 5.5oC and 1atm. ΔSfus = A(1.98), B(2,980), C(60.0), D(39.1) J/K.mol.
[C] What is the standard free energy change (ΔGo) for a reaction that has an equilibrium constant
(Keq) of 2.6 x 10-4 at 25C?
A(-1.7 x 103), B(-2.0 x 104), C(-16.9),
D(+2.0 x 104) J/mole.
[D. What is the nonstandard free energy change for the following reaction at 25oC if the pressure of
the hydrogen is 0.19 atm and the pressure of the CH4 is 0.35 atm?
C(s) +2H2(g) = CH4(g)
ΔGo = -50.5kJ/mol
A(–49), B(-45), C(-26), D(-56) kJ.
[E] What combination of H and S will be a spontaneous process at low temperatures?
A(H = positive, S = positive), B(H = positive, S = negative),
C(H = negative, S = positive), D(H = negative, S = negative).
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Electrochemistry
21. In general, metals (alkali metals in particular) tend to be oxidized, and non-metal (halogens in
particular) tends to be reduced.
A(True),
B(False)
22. Which one has an incorrect oxidation # for an underlined atom in it?
A(HNO2, +3), B(Cr2O72-, +6), C(NO3-, +5), D(H2O2, -1), E(NaClO, -1)
23. If an oxidation # of an atom in a substance is higher than its normal one. the substance will be a
good A(oxidizing agent), B (reducing reagent),
24. Balance the following redox equation in acid solution and determine the molar ratio of HNO2 to
Cr2O72-:
HNO2 (aq) + Cr2O72- (aq)  Cr3+ (aq) + NO3- (aq)
A(3:1), B(1:3), C(3:2), D(2:3)
25. The higher the standard reduction potential of a substance, the stronger the oxidizing agent.
A(True), B(False)
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26. You built a standard Zn-Mn voltaic cell.
Given Standard Reduction Potentials: Zn2+(aq) +2e- → Zn(s) Eo = -0.76 V
Mn2+(aq) +2e- → Mn(s) Eo = -1.18 V
Which of the following are correct statements? A(a. c) , B(a, d), C(b,c), D(b, d))
(a) Zn will reduce Mn2+ to Mn
(c) Mn will reduce Zn2+ to Zn
(b) Zn2+ will oxidize Mn to Mn2+
(d) Mn2+ will oxidize Zn to Zn2+
27. The Zn electrode is (a) anode, (b) cathode, and electrons will be moving from c(Zn to Mn) ,
d(Mn to Zn) electrode.
A(a, c), B(a, d), C(b,c), D(b, d)
28. What is the overall reaction?
A(Zn2+(aq) + Mn(s) → Zn(s) + Mn2+(aq))
B(Zn(s) + Mn2+(aq) → Zn2+(aq) + Mn(s))
29. What is the standard cell potential(Ecello)? A(0.42), B(-0.42), C(+1.98), D(-1.98) V.
30. The cell is being discharged now, and [Zn2+] is decreased to 0.10 M (from1.00 M).
Find new [Mn2+] concentration to calculate a new (nonstandard) cell potential.
A(0.90M; 0.34V), B(1.90M; 0.38V ), C(0.10M; 0.46V), D(0.10M; 0.34V)
31. The cell is completely discharged to reach an equilibrium so that Ecell=0.00V, and ΔG= 0.00J,
and Q(the reaction quotient) become Keq. Find Keq from the Ecello value above.
A(1.5x1014), B(1.5x10-14), C(1.5x107), D(1.5x10-7)
32. Find the approximate final concentration of Zn2+ at the equilibrium.
A(0.00 M), B(1x10-18 M), C(1x10-14 M ), D(1x10-10 M), E(1x10-6M)
33. Volume of the solution in both anodic and cathodic cells were 100.0mL each. Find moles of Mn
or Mn2+ (or Zn or Zn2+) reacted to reach the equilibrium.
A(0.050), B(0.10), C(0.20;), D(0.400).
34. Find # of electrons moved across the cell (or flown) to reach the equilibrium.
A(3.0x1022), B(6.0x1022), C(1.2x1023), D(2.4x1024).
35. Masses of the electrodes at the beginning were 10.000g each.
What are the final masses of the cathode and anode respectively?
A(4.506g; 16.539)g, B(16.539g, 4.506g ), C(4.539g; 16.506V), D(16.506g; 4.539g).
36. Find ΔG to estimate the amount of the work done(J) by the cell whenthe standard cell is
completely discharged
ca. A(6J), B(60 J), C(6 kJ), D(650kJ), E(6 MJ).
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37. Choose one.
[A] Which of the following represents the balanced chemical equation for the following cell?
Pt | H2 | H+ | | Br2 | Br - | Pt
+
-
A(H2(g) + Br2(aq)
 H (aq) + Br- (aq)
+
B(Pt + H2 + 2H
+  Br2 + 2 Br + Pt)
C(H2 ++ Br2-  2H + 2Br-)
D(2H + 2Br
 H2 + Br2 )
[B] State the half-reaction that occurs at the anode for the reaction.
Zn(s) + 2H+(aq)  H2(g) + Zn2+(aq)
A(H2(g)  2H+(aq) + 2e-), B(H2(g) + 2e-  2H+(aq))
C(Zn(s) Zn2+(aq) + 2e-), D(Zn2+(aq) + 2e-  Zn (s))
38. Use the reduction potentials given below to calculate the standard cell potential for the reaction:
Sn2+(aq) + 2Fe3+(aq)  2Fe2+(aq) + Sn4+(aq)
Fe3+ + e-  Fe2+
Eo = +0.771 V
4+
2+
Sn + 2e  Sn
Eo = +0.154 V
A(+0.925), B(+0.617), C(-0.925), D(-0.617) V.
39. Find the Keq for the reaction above from Ecello.
A(1.8x1031), B(7.0x1020), C(5.6x10-32), D(1.4x0-21)
40. Calculate the charges(Coulomb), and the mass of copper deposited through the passage of 0.500
Ampere through a solution of Cu2(aq) for 10.0 min.
A(300C; 0.395g), B(300C, 0.198g ), C(300C; 0.099g), D(600C g; 0.395g).
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Formula:
ΔGo = - RT lnK
E= Eo – (RT/nF)lnQ
E= Eo – (0.0592/n )logQ
(end)
at 25oC