1.
Determine the molarity of Al2S3(aq) in a solution which contains 0.100 M NaCl (aq), 0.100 M Na3PO4(aq), and Al2S3(aq), assuming all electrolytes as strong and as easily soluble ones, when the ionic strength of the solution is 1.400 M?
A.
0.0467 M
B.
0.0833 M
C.
0.00667 M
D.
0.0233 M
E.
0.100 M


2.
Consider a weak acid with a molar conductivity of 3.76 S cm2 mol-1 at 298K and 0.0100 M concentration. The molar conductivity is found to be 1.27 S cm2 mol-1 when the concentration is 0.0500 M. Given the molar conductivity at infinite dilution to be 39.56 S cm2 mol-1 deter-mine the dissociation equilibrium constant, calculated in terms of molarities, of the acid.
A.
1.28 x 10-2
B.
1.25 x 10-3
C.
3.17 x 10-5
D.
3.15 x 104
E.
3.17 x 10-4


3.
Given the ionic radii of lithium and strontium in the gas phase as 0.59 pm and 1.18 pm respectively. Then, the following statement is true:
A.
The Gibbs energy of solvation for strontium ions is twice that for lithium ions.
B.
More heat is released when lithium ions are dissolved as compared to strontium ions.
C.
Lithium ions dissolve better than strontium ions.
D.
There will be more deviations from the Debye-Hückel limiting model in the case of lithium ions as compared to strontium ions.
E.
The logarithm of the activity coefficient for lithium ions is expected to drop faster with concentration increase as compared to strontium ions (in the same electrolyte) in solution.


4.
The solubility product of 0.00100 M PbCl2 in pure water is 1.60 x 10-5 in terms of molarity. In order to decrease the amount of lead in the solution by the largest amount, we may add (assume that no precipitates are formed):
A.
0.001 M Na3 PO4
B.
0.00100 M Na2SO4
C.
0.00100 M NaCl
D.
1.35 M NaCl
E.
0.0034 M NaCl


5.
An electrochemical cell consists of a silver electrode in contact with 200 mL of 0.100 M AgNO3 solution and a magnesium electrode in contact with 100 mL of 0.100 M Mg(NO3)2 solution (both aqueous solutions at 25oC). Determine the EMF of the cell at 298.15 K.
[Reduction potentials: E°Ag+/Ag=+0.80V and E°Mg2+/Mg=-2.37V]
A.
8.13 V
B.
2.80 V
C.
4.15 V
D.
1.14 V
E.
3.14 V


6.
Consider the following cell reaction:
2MnO4-(s) + 5 Zn(s) + 16H+(aq) ------◊ 2Mn2+(aq) +5Zn2+(aq) + 8H2O(l)
The E° = 2.27 V. Which of the following conditions would increase the voltage of the cell:
A.
Increasing the Mn2+(aq) concentration
B.
Decreasing the MnO4- concentration
C.
Reducing the pH of the solution
D.
Adding more solid Zn(s)
E.
Decreasing the amount of Zn(s)


7.
If the standard potential of a cell is E° = 3.65 V at 298.15 K and (dE°/dT)p = -6.20 x10-5 VK-1, the thermodynamic parameter ΔHoR in J/mol for a single electron transfer is:
A.
-3.50 x 105
B.
-3.54 x 105
C.
2.54 x 105
D.
7.50 x 105
E.
3.50 x 105


8.
How can it be decided if an electrolyte is a weak electrolyte and how can the molar conductivity at infinite dilution be determined?
A.
If a plot of the inverse molar conductivity vs. the electrical conductivity is linear, and the molar conductivity at infinite dilution is the inverse of the intercept of this straight line.
B.
If a plot of the inverse molar conductivity vs. the electrical conductivity is linear, and the molar conductivity at infinite dilution is the intercept of this straight line.
C.
If a plot of the inverse molar conductivity vs. the electrical conductivity is linear, and the molar conductivity at infinite dilution is the inverse of the slope of this straight line.
D.
If a plot of the molar conductivity vs the square root of c/co (co = 1 M, and c is the concentration of the electrolyte) is linear and the molar conductivity at infinite dilution is the slope of this straight line.
E.
If a plot of the molar conductivity vs the square root of c/co (co = 1 M, and c is the concentration of the electrolyte) is linear and the molar conductivity at infinite dilution is the intercept of this straight line.


9.
How can a plot of ΔGosolvation vs z2/r be made better linear for different ions to improve the model?
A.
Use of z2/reff instead of z2/r, where reff is the average distance between the center of the ion and the center of charge of a water molecule in the solution.
B.
Use of z2/reff instead of z2/r, where reff is the average distance between two water molecules in the solution.
C.
Use of z2/reff instead of z2/r, where reff is the average distance between two ions in the solutions.
D.
Use of z2/reff instead of z2/r, where reff is the maximum distance an ion can move during electrolysis.
E.
Use of zeff2/r instead of z2/r, where zeff is the average charge of cation and anion.


10.
Use the Debye-Hückel Limiting Law (DHLL) and do three steps of an iteration to calculate an approximate value of the solubility of aluminum fluoride (AlF3) (Ksp = 3.51 x 10-10) in water at 25 oC. Assume aluminum fluoride to be a strong electrolyte and assume all concentration units to be M with co = 1 M.
A.
1.99 x 10-2 M
B.
1.90 x 10-3 M
C.
0.018 M
D.
0.0114 M
E.
2.99 x 10-3 M


11.
What will happen in the electrochemical cell at 25 oC:
Co(s)|Co2+(aq, a = 1.00)||Ni2+(aq, a = 0.001)|Ni(s)
if EoCo2+/Co = -0.280 V and EoNi2+/Ni = -0.257 V.
A.
Cobalt (Co) is deposited at the Co electrode.
B.
The concentration of nickel (Ni) ions decreases.
C.
The concentration of cobalt (Co) ions increases.
D.
Nickel (Ni) is deposited at the Ni electrode.
E.
Nickel (Ni) is deposited at the Co electrode.


12.
Given
MnO4- + 8 H+ + 5 e- → Mn2+ + 4 H2O Eo = 1.52 V
and
MnO2 + 4 H+ + 2 e- →Mn2+ + 2 H2O Eo = 1.23 V,
calculate Eo for the half-cell reaction
MnO4- + 4 H+ + 3 e- → MnO 2 + 2 H2O.
A.
1.71 V
B.
-1.71 V
C.
3.35 V
D.
-3.35V
E.
5.13 V


13.
Use the cell at 25oC:
Fe(s)|Fe3+(aq, aFe3+)||S2-(aq, aS2-)|Fe2S3(s)|Fe(s)
to determine the solubility product of Fe2S3, when EoFe3+/Fe = 0.041 V and EoFe2S3/Fe = -0.321 V.
A.
0.92
B.
4.98 x 1036
C.
2.82 x 10-33
D.
1.77 x 10-37
E.
1.93 x 10-37


14.
The molar conductivity at 20 °C of a 0.0100 M aqueous solution of ammonia (NH4OH) is 9.6 S cm2 mol-1. For NH4Cl, Λmo = 129.8 S cm2 mol-1 and the ionic equivalent conductance values for OH- and Cl- are 174 and 65.6 S cm2 mol-1, respectively. Calculate the degree of ionization (α) for NH3 in the 0.0100 M solution.
A.
α = 0.0403
B.
α = 0.0184
C.
α = 0.781
D.
α = 0.503
E.
α = 0.0784


15.
Which of the following solutions have the same ionic strength (I) as 0.10 M NaCl(aq)?
A.
0.0167 M Na3PO4 (aq)
B.
0.280 M CuSO4(aq)
C.
0.055 M CuSO4(aq)
D.
0.102 M Al2(SO4)3 (aq)
E.
1.23 M BaSO4(aq)


16.
Calculate the pH of the HCl solution in the following cell at 25°C; Pt(s), H2(1 atm)| HCl(aq)| AgCl(s)|Ag(s) ; of which Ecell is 0.517 V.
(AgCl|Ag electrode has Eo = 0.2224 V and γ± = 1)
A.
1.23
B.
4.32
C.
5.21
D.
 
E.
2.49


17.
Express a± in terms of a+ and a- for K4Fe(CN)6
A.
B.
C.
D.
E.


18.
Consider the cell:
Fe(s) │ FeSO4(aq, a± = 0.0250) │ Hg2SO4 (s) │ Hg (l)
if the standard reduction potential of the different electrodes are = -0.447 V and = 0.7973 V, the ΔGR in kJ mol-1 at 25.0 oC is
A.
-258.4
B.
+258.4
C.
-221.8
D.
+221.8
E.
–249.3


19.
Calculate ΔGoR in kJ mol-1 at 25.0 oC for the reaction:
ZnCl2 (s) ◊ Zn2+ (aq) + 2 Cl- (aq)
[(ΔHof (kJ mol-1) & ΔSo (J mol-1 K-1)) of Zn2+ (aq), Cl- (aq), and ZnCl2 (s) are (-152.3 & -109.8), (-167.1 & 56.6), and (-415.1 & 111.5), respectively]
A.
-147.1
B.
-409.5
C.
+409.5
D.
 
E.
-39.2


20.
The Debye-Hückel screening length (1/κ) for a 1-1 electrolyte is 0.964 nm at a concentration of 0.1 m in water at 25 oC (εr = 78). Estimate the screening length in nm of the same electrolyte in a solvent of εr = 38, assuming that the density of both solvents is 1.0 kg m-3.
A.
0.511
B.
0.341
C.
0.456
D.
0.673
E.
0.213


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