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Selection Procedure for the Graduate Course in Chemistry at UFPE - 2009.2
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Graduate Course in Chemistry
Department of Fundamental Chemistry
Center of Exact and Natural Sciences
DQF
PG
Federal University of Pernambuco - Brazil
SELECTION PROCEDURE FOR THE MASTER AND DOCTORAL COURSE IN
CHEMISTRY AT UFPE
TEST OF GENERAL CHEMISTRY – 05/25/2009
CANDIDATE:______________________________________________________________
1 - Calculate the solubility of Ba(IO3)2 in the solution that results when 200 mL of 0.01 mol/L
Ba(IO3)2 is mixed with 100 ml of 0.01 mol/L NaIO3?
2 – The action of an alkaline I2 solution upon the rodenticide warfarin, , C19H16O (308.34 g/mol),
results in the formation of 1 mol of iodoform, CHI3 (393.73 g/mol), for each more of the parent
compound reacted. Analysis for warfarin can then be taken based upon the reaction between CHI3
and Ag+:
CHI3 + 3Ag+ + H2O
Æ
3AgI (s) + 3H+ + CO (g)
The CHI3 produced from a 13.96 g sample was treated with 25.00 mL of 0.02979 mol/L AgNO3,
and the excess Ag+ was then titrated with 2.85 of 0.05411 mol L-1 KSCN. Calculate the percentage
of warfarine in the sample.
3 - Acetic acid, CH3COOH(l), could be produced from: (a) the reaction of methanol with carbon
monoxide; (b) the oxidation of ethanol; (c) the reaction of carbon dioxide with methane.
a) Write balanced chemical equations for each process;
b) Carry out thermodynamic analysis of the three possibilities and decide which you would expect
to be the easiest to accomplish.
4- Suppose that 25.0 mL of a solution of Ag+ ions of unknown concentration is titrated with 0.015
M KI(aq) at 25oC. A silver electrode is immersed in this solution, and its potential is measured
relative to a standard hydrogen electrode. A total of 16.7 mL of KI (aq) was required to reach the
stoichmetric point, when the potencial was 0.325 V.
(a) What is the molar concentration of Ag+ in the solution?
(b) Determine Kps for AgI by using the electrochemical data.
Selection Procedure for the Graduate Course in Chemistry at UFPE - 2009.2
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5 - Consider de following chemical equillibria:
CaF2 (s) ' Ca2+ (aq) + 2F– (aq)
Kps = 4.0 × 10–11
F– (aq) + H2O (l) ' HF (aq) + OH– (aq)
Kb = 2.9 × 10–11
a) Write the chemical equation for the total (global) equilibrium and calculate the corresponding
equilibrium constant.
b) Calculate the solubility of CaF2 at pH = 7.0 and pH = 3.0.
6 - The hydrolysis of an organic nitrile in basic media has the following mechanism:
Step 1:
Step 2:
Step 3:
a) Write the complete and balanced chemical reaction for the total (global) reaction and identify the
reactants, products, intermediates, and catalyst.
b) Which are the reaction order and the molecularity for each step in the reaction mechanism?
Explain and justify.
c) Which should be the rate determining step? Explain and justify.
d) Draw the reaction profile (energy vs. reaction coordinate) correlating each extreme point with the
species involved in the reaction mechanism.
7 - When 1-cyclohexylethanol (A) is treated with concentrated aqueous HBr, the major product is 1bromo-1-ethylcyclohexane (B).
OH
HBr
Br
H2 O
A
B
a) Give a mechanism for this reaction;
b) How would you convert 1-cyclohexylethanol (A) to (1-bromoethyl)cyclohexane (C) in good
yield?
Selection Procedure for the Graduate Course in Chemistry at UFPE - 2009.2
8 – An unknown compound has the following 1H,
-1
13
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C and mass spectra. It also has a strong IR
absorption band in the 3300 cm region. Give the structure of the compound and interpret the
spectra.
1
H NMR spectrum
(300 MHz)
The numeric values refer
to integral values
13
C NMR spectrum
(75 MHz)
Mass spectrum
(electron impact, 76 eV)
Mass of molecular ion:
74
Selection Procedure for the Graduate Course in Chemistry at UFPE - 2009.2
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9 - Consider the structure of the four organic molecules below:
H
H
H
H
C
C
C
H
H
I
H
C
H
C
H
H
HH
H
C
H
H
II
H
H
C
C
H
H
H
C
H
H
H
III
H
C
C
H
C
H
IV
Use the model of a free particle in a box to associate the spectra below (which absorb at a) 290 nm
and b) 162 nm) with the corresponding structures. Justify your answer.
A
b
10 – Explain why K2 > K1 for the substitution reaction of water for ammonia and for 1,2diammineethane (en) on the hexaquo nickel (II) ion shown below.
[Ni(H2O)6]2+ (aq) + 6 NH3 ( l ) ' [Ni(NH3)6]2+ (aq) + 6 H2O ( l ) K1 = 5.5x108
[Ni(H2O)6]2+ (aq) + 3 en ( l )
' [Ni(en)3]2+ (aq) + 6 H2O ( l )
K2 = 4.0x1018
Support Information
Constants:
h = 6.62.10 -34 J s = 6.62.10-27erg s;
c = 3.108 m s-1 = 3.1010 cm s-1;
me = 9.1.10-31 kg = 9.1.10-28 g;
e = 1.6.10-19 C = 4.8.10-10 u.e.c.;
ε0 = 8.85.10-12 C2J-1m-1;
R = 8.31451 J.K-1.mol-1 = 0.082 atm L K-1mol-1
F = 9.6485 x 104 C mol-1;
NA = 6.02 x 1023 mol-1.
Atomic number:
H = 1;
C = 6;
N = 7;
O = 8;
F = 9;
Na = 11;
K = 19;
Ca = 20;
Br = 35;
Ag = 47;
I = 53;
Ba = 56.
Equilibrium constant:
Kps(Ba(IO3)2) = 1.57.10-9
S=16;
Selection Procedure for the Graduate Course in Chemistry at UFPE - 2009.2
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Molecular mass (g mol–1):
H = 1.008;
C = 12.011;
N = 14.007; O = 15.999;
F = 18.998; Na = 22.990; S = 32.066;
K = 39.098; Ca = 40.078; Br = 79.904; Ag = 107.868; I = 126.905; Ba = 137.327.
Equations:
ΔG = ΔG° + RT lnQ
ln k = ln A −
p=
Ea
RT
h
RT
0,059
ln Q or ε = ε θ −
log Q
nF
n
1
E C = mv 2
p = mv
2
ΔG = -nFε
ε = εθ −
E foton = hν =
hc
λ
E foton = w0 + Ec .
λ
Transformation:
1 Å =10-10 m
1cal = 4.184 J;
Thermodynamic data at 298 K:
Chemical
specie
Cp.m
ΔH 0fus
ΔG 0f
ΔH 0f
o
Sm
JK-1mol-1 kJmol-1 kJmol-1 kJ mol-1 J K-1 mol-1
CH3OH (l)
81.6
3.16
-166.27
-238.86
126.8
C2H5OH (l)
111.5
4.60
-174.78
-277.69
160.7
-
-
-389.9
-484.5
159.8
H2O (l)
75.3
6.01
-237.13
-285.83
69.91
H2O (g)
33.6
-
-228.57
-241.82
188.83
CH4 (g)
35.31
-
-50.72
-74.81
186.26
CO (g)
29.14
-
-137.17
-110.53
197.67
CO2 (g)
37.11
-
-394.36
-393.51
213.7
O2 (g)
29.36
0
0
205.14
CH3COOH (l)
Standard reduction potential at 298 K:
Semi-reduction
E0 (Volts)
Ag+(aq) + é Æ Ag (s)
+0.80
Cu2+ (aq) + 2é Æ Cu (s)
+0.34
2 H+ (aq) + 2é Æ H2 (g)
0.0
Sn2+ (aq) + 2é Æ Sn (s)
-0.14