Download MT 3 Practice

1. Ammonia was added to a solution of one of the ions from the list at the start of the flowchart.
No precipitate formed. Ammonium carbonate was added and a precipitate formed. The
precipitate was then dissolved by the addition of HCl. Sodium sulfate was then added and a
precipitate formed. What is the identity of the cation.
[A] Co2+
[B] Ca2+
[C] Ba2+
[D] Ni2+
2. 1M NH3 was added to to a solution of one of the ions from the list of ions at the start of the
flow chart A precipitate formed. Sodium hydroxide was then added and the precipitate
dissolved. Acetic acid was then added and a precipitate formed. What is the identity of the
Cation.
[A] Al3+.
[B] Mn2+.
[C] Fe3+.
[D] Ca 2+.
3. The following information will be helpful for the questions below.
The proposed mechanism for the decomposition of N2O5 is
N2O5 NO2 + NO3
slow step
NO2 + NO3 NO2 + O2 + NO
fast step
NO + N2O5 3NO2
fast step The stoichiometric equation for the
decomposition of N2O5 is
[A] N2O5
NO2 + O2 + NO.
[B] N2O5
NO2 + NO3.
[C] 2N2O5
4NO2 + O2.
[D] N2O5 + NO2 + NO3
4NO2 + O2.
4. The rate law that is applicable to the mechanism above is
[A] k3[NO][N2O5].
[B] k1[N2O5].
[C] k2[NO2][NO3].
[D] k1k2[N2O5][NO2][NO3].
5.
What is the thermodynamic quantity that provides the criterion for the spontaneity of a
chemical reaction?
a. DU b. DS c. DH d. DG
6. Which of the following processes is endothermic?
[A] Al3+(g) + 3e-
Al(s)
[B] H2O(g)
H2O(l)
[C] 2H2O(l)
2H2(g) + O2(g)
[D] NH3(g) + HCl(g)
NH4Cl(s)
7. The heat of vaporization of ammonia is 23.4 kJ/mol. Its boiling point is -33°C. The change in
entropy for the vaporization of methanol in J/(mol • K) is
[A] -23.4.
[B] 23.4.
[C] 97.5.
[D] 0.00975.
8. Which of the following processes would be expected to have a positive DS value?
[A] 2ClBr(g) Cl2(g) + Br2(g)
[B] NH4HS(s) NH3(g) + H2S(g)
[C] I2(g)
I2(s)
[D] 2H2(g) + O2(g)
2H2O(g)
9. Calculate DS° for the decomposition of ozone from oxygen.
2O3(g) 3O2(g)
S° = 205 J/(mol • K) for O2(g) and 239 J/(mol • K) for O3(g) at 25°C.
[A] -137 J/(mol • K)
[B] -134 J/(mol • K)
[C] -34 J/(mol • K)
[D] +137 J/(mol • K)
10. For the following reaction at 25°C
I2(g) + Cl2(g) 2ICl(g)
DH° = -26.9 kJ and DS° = 11.3 J/K. Calculate DG° for the reaction in kilojoules.
[A] -50.6 kJ
[B] 102 kJ
[C] 50.6 kJ
[D] -30.3 kJ
11. Given the following
Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g)
3Fe2O3(s) + CO(g) 2Fe3O4(s) + CO2(g)
calculate DG° for
Fe(s) + Fe2O3(s) + CO2(g) Fe3O4(s) + CO(g)
DG° = -29.4 kJ
DG° = -61.6 kJ
[A] +32.2 kJ
[B] -32.2 kJ
[C] -16.1 kJ
[D] +16.1 kJ
12. The reaction
CH4(g) + N2(g) + 164 kJ HCN(g) + NH3(g)
at 25°C and 1 atm pressure is to be used for the following questions. Which of the following
statements describes the reaction?
[A] It is spontaneous at relatively low temperatures only.
[B] It is spontaneous at all temperatures.
[C] It is nonspontaneous at all temperatures.
[D] It is spontaneous at relatively high temperatures only.
13. What is the minimum temperature required for the spontaneous conversion of CCl4(l) to
CCl4(g) when DH° is 573 kJ/mol and DS° is 1.64 kJ/(mol • K)?
[A] 215°C
[B] 189°C
[C] 349°C
[D] 76°C
14. For a reaction if DG° = 0, then
[A] DH° = 0.
[B] DS° = 0.
[C] K = 1.
[D] DG = 0.
15. Which of the following must have a negative value for an exothermic reaction?
[A] free energy change
[B] entropy change
[C] electrode cell potential
[D] enthalpy change
16. Which of the following processes is endothermic?
[A] NH3(g) + HCl(g)
[B] 2H2O(l)
2H2(g) + O2(g)
[C] Al3+(g) + 3e[D] H2O(g)
NH4Cl(s)
Al(s)
H2O(l)
17. The following reaction was found to have a positive G at 25o C. What can we say about the
concentration of A and B? G= -RT ln K/Q
A(aq) ----> B(aq) Go = -3.6kJ/mole
[A] [B] = [A]
[B] [B] > [A]
[C] [B] < [A]
[D] none of these
18. For the following reaction
CaC2(s) + 2H2O(l) Ca(OH)2(s) + C2H2(g)
which is spontaneous at all temperatures, one would predict that
[A] DH is + and DS is - for the reaction.
[B] DH is - and DS is - for the reaction.
[C] DG is - for all temperatures.
[D] DH is + and DS is + for the reaction.
19. The following reaction occurs in acid solution:
NO3- + I- IO3- + NO2
In the balanced equation, the coefficient of NO3- is
[A] 2.
[B] 3.
[C] 4.
[D] 6.
20. Which of the following species would NOT function as an oxidizing agent?
[A] Mn+2
[B] MnO4[C] Br[D] H+
21. Which of the following is TRUE for a galvanic cell?
1. The electron flow is from the negative electrode to the positive electrode.
2. The electron flow is from the anode to the cathode.
3. The electron flow is from oxidizing agent to the reducing agent through an external
circuit.
[A] 2 only
[B] 3 only
[C] 1 only
[D] 1 and 2 only
22. The numerical value of the Faraday constant is given as 96,500. This value represents
[A] the number of ions discharged by the passage of one mole of electrons.
[B] the number of electrons corresponding to one mole of electric charge.
[C] the number of coulombs of charge carried by one mole of electrons.
[D] the number of electrons corresponding to one coulomb of charge.
23. The following has a potential of 0.92 V:
2Hg2+(aq) + H2(g) 2H+(aq) + Hg22+(aq)
If the concentrations of the ions were 1.0 molar and the pressure of H2 were 1.0 atmosphere,
then E° for the half-reaction
2Hg2+(aq) + 2e- Hg2+2
would be
[A] -0.46 V.
[B] -0.92 V.
[C] 0.92 V.
[D] 0.46 V.
24. A standard cell that consisted of a strip of zinc dipped into 1.0 M zinc ion and a strip of
copper dipped into 1.0 M copper ion, and which was connected by a salt bridge, had a potential
of 1.10 V.
Zn + Cu2+ Zn2+ + Cu
If a potential of 0.60 V were assigned to the half-reaction
Cu2+ + 2e- Cu
instead of 0.34 V, which is the potential given in a standard reduction potential table, the
potential for the reaction
Zn2+ + 2e- Zn
would be
[A] -0.76 V.
[B] 0.50 V.
[C] 0.60 V.
[D] -0.50 V.
25. Consider the following standard reduction potentials:
2H+(aq) + 2e- H2(g)
E° = 0.00 V
Sn2+(aq) + 2e- Sn(s)
E° = -0.15 V
Cd2+(aq) + 2e- Cd(s)
E° = -0.40 V
Which pair of substances will react spontaneously?
[A] Sn2+ with H+
[B] Cd with Sn2+
[C] Sn with Cd2+
[D] Sn2+ with Cd2+
26. For a certain reaction, DH° = -76.0 kJ and DS° = -234 J/K. If n = 3, calculate E°tot for the
reaction at 25°C.
[A] 0.065 V
[B] 0.032 V
[C] 0.096 V
[D] 0.022 V
27. What is the value of the reaction quotient, Q, for the cell that is constructed from the two
half-reactions
Zn2+ + 2e- Zn
-0.76 V
Ag+ + e- Ag
0.80 V
when the Zn2+ concentration is 0.0100 M and the Ag+ concentration is 1.25 M?
E = Eo - RT/nF ln Q
[A] 125
[B] 6.40 ´ 10-3
[C] 156
[D] 8.00 ´ 10-3
28. The following information is for the question below.
For the cell reaction
2MnO4- + 5H2SO3 2Mn2+ + 5SO42- + 4H+ + 3H2O
the standard cell potential is 1.34 V. To determine the cell potential at nonstandard conditions,
the value that should be used for n in the Nernst equation is
[A] 5.
[B] 6.
[C] 10.
[D] 2.
29. Calculate the equilibrium constant K at 25°C for the reaction
Sn + Pb2+(aq) Sn2+(aq) + Pb(s)
where E°cell equals 0.014.
[A] 8.8
[B] 3.0
[C] 1.7
[D] 4.8
30. Which of the following statements is true about a galvanic cell that has an E° value of +1.00
V?
1. The reaction is spontaneous.
2. At equilibrium K = 1.
3. It has a negative DG°.
[A] 1 and 3 only
[B] 1 only
[C] 2 only
[D] 1 and 2 only
31. For the cell reaction
P4 + 3OH- + 3H2O PH3 + 3H2PO2E°cell = 1.66 V. The oxidizing and reducing agents are, respectively,
[A] P4 and P4.
[B] P4 and OH-.
[C] H2O and P4.
[D] OH- and P4.
32. What is the Cu2+ concentration at 25°C in the cell made from the following reaction? The cell
emf is 1.03 V. The standard cell emf is 1.10 V.
Cu2+ + Zn ----> Cu + Zn2+
[A] 0.004 M
[B] 0.07 M
[C] 2.4 M
[D] 1.0 M
33.
From a consideration of these data, determine which of the following species will oxidize Fe to
Fe2+.
[A] Mg2+
[B] Al3+
[C] Cu2+
[D] Zn2+
34. The following information is for the questions below.
Cr3+ + 3e- Cr
-0.74 V
Pb2+ + 2e- Pb
-0.13 V Calculate K for the reaction above when the initial
concentration of Cr3+ and Pb2+ are 1.00 M. DGo = -nFe=-RTlnK
[A] 3.6 x 10-31
[B] 1.6 x 10-13
[C] 5.4 x 10-18
[D] 7.5 x 1061
35. What is the value of the reaction quotient, Q, for the cell that is constructed from the two
half-reactions
Zn2+ + 2e- Zn
-0.76 V
Ag+ + e- Ag
0.80 V
when the Zn2+ concentration is 0.0100 M and the Ag+ concentration is 1.25 M?
[A] 125
[B] 1.25 ´ 10-2
[C] 6.40 ´ 10-3
[D] 156
Reference: [20.54a]
[1] [C]
Reference: [20.55a]
[2] [A]
Reference: [14.75a]
[3] [C]
Reference: [14.76a]
[4] [B]
Reference: [19.2a]
[5] d.
Reference: [19.10a]
[6] [C]
Reference: [19.16a]
[7] [C]
Reference: [19.26a]
[8] [B]
Reference: [19.40a]
[9] [D]
Reference: [19.41a]
[10] [D]
Reference: [19.47a]
[11] [C]
Reference: [19.50a]
[12] [D]
Reference: [19.78a]
[13] [D]
Reference: [19.79a]
[14] [C]
Reference: [19.6a]
[15] [D]
Reference: [19.10b]
[16] [B]
Reference: [19.20a]
[17] [C]
Reference: [19.61a]
[18] [C]
Reference: [20.6a]
[19] [D]
Reference: [20.12a]
[20] [C]
Reference: [20.17a]
[21] [D]
Reference: [20.26a]
[22] [C]
Reference: [20.33a]
[23] [C]
Reference: [20.35a]
[24] [D]
Reference: [20.37a]
[25] [B]
Reference: [20.43a]
[26] [D]
Reference: [20.51a]
[27] [B]
Reference: [20.49a]
[28] [C]
Reference: [20.53a]
[29] [B]
Reference: [20.57a]
[30] [A]
Reference: [20.71a]
[31] [A]
Reference: [20.60a]
[32] [A]
Reference: [20.83a]
[33] [C]
Reference: [20.48a]
[34] [D]
Reference: [20.51b]
[35] [C]