Download USNCO 2004 National

ampere
atmosphere
atomic mass unit
atomic molar mass
Avogadro constant
Celsius temperature
centi- prefix
coulomb
electromotive force
energy of activation
enthalpy
entropy
equilibrium constant
ABBREVIATIONS AND SYMBOLS
F molal
A Faraday constant
M molar
atm formula molar mass
u free energy
G molar mass
A frequency
v mole
R Planck's constant
7VA gas constant
g pressure
°C gram
C p rate constant
c heat capacity
h retention factor
C hour
J second
E joule
Ea kelvin
K temperature, K
k time
H kilo- prefix
liter
L volt
S
milli— prefix
m
K
CONSTANTS
m
M
M
mol
h
P
k
Rf
s
T
/
V
# = 8.314 J-mol '-K l
tf = 0.0821 L-atm-mol'-K >
1 F= 96,500 C-mol 1
1 F= 96,500 J - V ' - m o l 1
7VA = 6.022 x l O 2 3 mol ]
h = 6.626 x 10 3 4 J-s
c = 2.998 x 108 m-s '
0 °C = 273.15 K
1 atm = 760 mmHg
EQUATIONS
,\nKv =
nF
i
1A
1
H
1.008
3
Li
— + constant
IT)
r JLIVIVJUH^ i /\i>i_jJL ur i niL JLI^JLIVIJLIII 1 »
2
2A
4
Be
13
3A
5
B
14
4A
6
C
15
5A
7
N
is
16
6A
8
O
17
7A
9
F
8A
2
He
4.003
10
Ne
6.941
9.012
10.81
12.01
14.01
16.00
19.00
20.18
11
Na
12
Mg
13
Al
14
Si
15
P
16
S
17
Cl
18
Ar
22.99
24.31
19
K
20
Ca
3
3B
21
Sc
4
4B
22
Ti
5
5B
23
V
6
6B
24
Cr
7
7B
25
Mil
8
8B
26
Fe
9
8B
27
Co
10
8B
28
Ni
11
IB
29
Cu
12
2B
30
Zn
26.98
28.09
30.97
32.07
35.45
39.95
31
Ga
32
Ge
33
As
34
Se
35
Br
36
Kr
39.10
40.08
44.96
47.88
50.94
52.00
54.94
55.85
58.93
58.69
63.55
65.39
69.72
72.61
74.92
78.96
79.90
83.80
37
Rb
38
Sr
39
Y
40
Zr
53
87.62
88.91
107.9
112.4
114.8
118.7
Sb
121.8
Te
127.6
I
126.9
54
Xe
85.47
106.4
50
Sn
52
102.9
49
In
51
101.1
46
Pd
48
(98)
44
Ru
47
95.94
43
Tc
45
Rh
92.91
42
Mo
91.22
41
Nb
131.3
55
Cs
56
Ba
57
72
73
74
Hf
Ta
W
76
Os
77
Ir
78
La
75
Re
79
Au
80
Hg
81
Tl
82
Pb
83
Bi
84
Po
85
At
86
Rn
Pt
Cd
132.9
137.3
138.9
178.5
180.9
183.8
186.2
190.2
192.2
195.1
197.0
200.6
87
88
Ra
89
Ac
104
Rf
105
Db
106
S?
(261)
107
Bh
108
Hs
109
Mt
110
111
112
114
(269)
(272)
(277)
(2??)
Fr
(223)
(226)
(227)
58
Ce
59
Pr
(262)
60
Nd
61
Pm
(262)
62
Sm
(265)
63
Eu
(266)
64
Gd
65
Tb
66
140.1
140.9
144.2
(145)
150.4
152.0
157.3
158.9
Dy
162.5
90
Th
91
Pa
92
U
93
Np
94
Pu
95
Am
96
Cm
97
Bk
98
Cf
232.0
Page 2
(261)
231.0
238.0
(237)
(244)
(243)
(247)
(247)
(251)
204.4
207.2
209.0
164.9
68
Er
167.3
69
Tm
168.9
173.0
175.0
99
Es
100
Fm
101
Md
102
No
103
Lr
67
Ho
(252)
(257)
(258)
70
Yb
(209)
(259)
(210)
(222)
71
Lu
(262)
Not valid for use as an USNCO Olympiad National Exam after April 19, 2004.
DIRECTIONS
When you have selected your answer to each question, blacken the corresponding space on the answer sheet using a soft, #2
pencil. Make a heavy, full mark, but no stray marks. If you decide to change an answer, erase the unwanted mark very carefully.
There is only one correct answer to each question. Any questions for which more than one response has been blackened will not
be counted.
Your score is based solely on the number of questions you answer correctly. It is to your advantage to answer every question.
1. Which element is obtained commercially from seawater?
(A) bromine
(B) gold
(C) iron
(D) oxygen
2. Which solution can serve as both reactant and indicator
when it is used in redox titrations?
(A) FeNH4(S04)2
(B) KMnO4
(C) H2C204
(D) Na2S2O3
(B) N 2 OandH 2 O
(C) NOandH 2
(D) N2, H 2 andO 2
(A) 3
(C) Ni
(D) Zn
(A) Blanket it with CO2
(B) Blow on it.
(C) Dump sand on it.
(D) Pour water on it.
5. Which letter indicates
where a thermometer
should be placed to
determine the boiling point
of a distillate?
(B) 6
(C) 12
(D) 18
9. An ionic compound contains 29.08% sodium, 40.56%
sulfur and 30.36% oxygen by mass. What is the formula
of the sulfur-containing anion in the compound?
4. Which method should be used to extinguish burning
magnesium metal?
(A) S2032
(B) S2042
(C) S2052
(D) S2062
Vapor pressure (mmHg)
10. A solution is prepared
containing a 2:1 mol ratio of
C2H4Br2
173
dibromoethane (C2H4Br2) and
dibromopropane (C3H6Br2).
C3H6Br2
127
What is the total
vapor pressure over the solution assuming ideal
behavior?
I
(C) C
(B) Mn
_ Br2 + _ OH' -» _ Br + _ BrO3" + _ H2O
is balanced with the smallest integer coefficients?
(A) N 2 andH 2 O
(B) B
(A) Ca
8. What is the coefficient for OH" after the equation
3. What is formed when a solution of NH4NO2 is heated
gently?
(A) A
7. A 1.871 gram sample of an unknown metallic carbonate
is decomposed by heating to form the metallic oxide and
0.656 g of carbon dioxide according to the equation
MCO3(s) -> MO(s) + CO2(g)
What is the metal?
(A) SOOmmHg
(B) 158mmHg
(C) ISOmmHg
(D) 142mmHg
(D) D
6. A 50 mL sample of gas is collected over water. What will
be the effect on the calculated molar mass of the gas if
the effect of the water vapor is ignored? It will be
(A) high because of the mass of water in the collection
flask.
(B) high because of omitting the vapor pressure of the
water in the calculation.
(C) low because of the mass of water in the collection
flask.
11. A solution of magnesium chloride that is 5.10%
magnesium by mass has a density 1.17 g/mL. How many
moles of Cl" ions are in 300. mL of the solution?
(A) 0.368
(B) 0.627
(C) 0.737
(D) 1.47
12. Which aqueous solution has a freezing point closest to
that of 0.30 MC 12 H 22 O n ?
(A) 0.075 M A1C13
(B) 0.15MCuCl2
(C) 0.30MNaCl
(D) 0.60 M C6H12O6
(D) low because of omitting the vapor pressure of the
water in the calculation.
Not valid for use as an USNCO Olympiad National Exam after April 19, 2004.
Page 3
13. An unknown gas is
placed in a sealed
container with a fixed
volume. Which of the
characteristics listed
change(s) when the
container is heated
from 25 °C to 250 °C?
I The density of the gas
II The average kinetic energy
of the molecules
III The mean free path between
molecular collisions
(B) II only
(C) III only
(D) I and II only
14. Which gas has the same density at 546 °C and 1.50 atm
asthatofO 2 gasatSTP?
(B) NH3
(A) S°20oK is smaller because entropy decreases as
temperature increases.
(B) S°20oK is smaller because the surroundings are more
disordered at higher temperatures.
(A) I only
(A) N2
20. Which is the best description of the relationship between
the absolute entropies, S°, of solid water at 100 K and at
200 K?
(C) S02
(D) S03
15. Which plot involving vapor pressure (VP) and absolute
temperature results in a straight line?
(A) VPvsT
(B) V P v s T 1
(C) In V P v s T
(D) In V P v s T 1
(C) S°IOOK = S°200K = because water is in the solid phase
at both temperatures.
(D) S°200K is larger because the vibration of the
molecules increases as temperature increases.
21. For the reaction,
CH4 + C12
-> CH3C1 + HC1
which expression
gives AH?
Bond dissociation
energies
C-H
C-C1
C1-C1
H-C1
kJ-mol 1
413
328
242
431
(A) AH = (413 + 328) - (242 + 431)
(B) AH = (413 - 328) - (242 - 431)
16. For a substance with the values of AHvap and ASVap
given below, what is its normal boiling point in °C?
(AHvap= 59.0 kJ-mol >; ASvap = 93.65 J-mor1 -K'1)
(A) 357
(B) 630
(C) 1314
(D) 1587
17. What is the order of the boiling points (from lowest to
highest) for the hydrogen halides?
(A) HF < HCK HBr < HI
(B) HKHBr<HCKHF
(C) H C K H F < H B r < H I
(D) HCKHBr<HKHF
18. Of the three types of cubic lattices, which have the
highest and lowest densities for the same atoms?
Highest
Lowest
(C) AH = (413-242)-(328-431)
(D) AH-(413+ 242)-(328+ 431)
22. Which phase change for water has positive values for
both AH° and AG°?
(A) (1)-> (s) at 250 K
(B) (1)-> (s) at 350 K
(C) (1)-> (g) at 350 K
(D) (1)-»(g) at 450 K
23. When solid CuSO4 dissolves in water to make a 1M
solution, the temperature of the system increases. When
solid NH4NO3 dissolves in water to make a 1 M solution,
the temperature of the system decreases. Which
statement(s) must be correct for these dissolving
processes?
I AH° values for both processes have the same sign.
II AG° values for both processes have the same sign.
(A) simple cubic
body-centered cubic
(B) face-centered cubic
simple cubic
(C) body-centered cubic
face-centered cubic
(A) I only
(B) II only
D) face-centered cubic
body-centered cubic
(C) Both I and II
(D) Neither I nor II
19. For which reaction is AH (enthalpy change) most nearly
equal to AE (internal energy change)?
24. Which set of relationships could apply to the same
electrochemical cell?
(A) H2(g) + l/202(g) - H20(g)
(A) AG°>0;E° = 0
(B) AG°<0;E° = 0
(B) Cl2(g) + F2(g) - 2ClF(g)
(C) A G ° > 0 ; E ° > 0
(D) A G ° < 0 ; E ° > 0
(C) H20(l) - H20(g)
(D) 2S03(g) -> 2S02(g) + 02(g)
Page 4
25. The rate constant for
a reaction is affected
by which factors?
I increase in temperature
II concentration of the reactants
111 presence of a catalyst
(A) I and II only
(B) I and III only
(C) II and III only
(D) I, II and III
Not valid for use as an USNCO Olympiad National Exam after April 19, 2004.
26. The rate data given were obtained for the reaction,
2NO(g) + 2H2(g) - N,(g) + 2H20(g)
What is the rate law for this reaction?
NO pressure (atm) H2 pressure (atm) Rate (atm* sec"1)
0.375
0.500
6.43 xlO- 4
0.375
0.250
3.15X10" 4
0.188
0.500
1.56X10" 4
(A)
= k:
(B) Rate-1
(C)
27. What is the order of a reaction that produces the graphs
shown?
31. H2S(aq) ^ HT(aq) + HS'(aq)
K = 9.5xlO- 8
HS-(aq) ^ HT(aq) + S2 (aq)
K^l.OxlO'19
Given the equilibrium constants provided, what is the
equilibrium constant for the reaction;
S 2 (aq) + 2H+(aq) ^ H2S(aq)
K =?
(A) 9.5 x 10'27
(B) 9.7 x lO'14
(C) 9.5 x 1011
(D) 1.0xl0 2 (
32. Calculate the hydronium ion concentration in 50.0 mL of
0.10MNaH 2 AsO 4 .
(KJ = 6.0 x lV3, K2 = 1.1 x lO'7 K3 = 3.0 x 10"12)
(A) 2.4 xlO- 2
(B) 1.6X10' 3
(C) 1.0 xlO" 4
(D) 2.5 xlO' 5
33. When the acids; HC1O3, H3BO3, H3PO4, are arranged in
order of increasing strength, which order is correct?
(A) H3BO3 < H3PO4 < HC1O3
(B) HC1O3 < H3BO3 < H3PO4
(A) zero order
(B) first order
(C) H3PO4 < HC1O3 < H3BO3
(C) second order
(D) some other order
(D) H3BO3 < HC1O3 < H3PO4
28. What is the rate law for the hypothetical reaction with the
mechanism shown?
intermediate 1 fast equilibrium
2A
intermediate 2 slow
intermediate 1 + B
A2B2
fast
intermediate 2 + B
34. A buffer solution results from mixing equal volumes of
which solutions?
I 0.1OMHC1 and 0.20 MNH 3
II 0.10 M HNO2 and 0.10 M NaNO2
III 0.20 M HC1 and 0.10 M NaCl
(A)
(B) Rate = [B]2
(A) II only
(B) I and II only
(C) Rate = k[A][B]
(D) Rate = k[A]2[B]
(C) I and III only
(D) I, II and III
29. According to the Arrhenius equation: k = Ae"Ea/RT, a plot
of In k against 1/T yields
(A) Ea as the slope and A as the intercept
(B) Ea/R as the slope and A as the intercept
(C) Ea/R as the slope and In A as the intercept
(D) -Ea/R as the slope and In A as the intercept
35. A solution is 0. 1 0 M in Ag+, Ca2+, Mg*, and A13+ ions.
Which compound will precipitate at the lowest [PO43 ]
when a solution of Na3PO4 is added?
(A) Ag 3 P0 4 (K a p =lxia 1 6 )
(B) Ca 3 (P0 4 ) 2 (K s p =lxia 3 3 )
(C) Mg 3 (P0 4 ) 2 (K^lxlO- 24 )
(D)
30. Curves with the shape
shown are often observed
for reactions involving
catalysts. The level portion
of the curve is best
attributed to the fact that
36. Which salt is significantly more soluble in a strong acid
than in water?
(A) PbF2
Reactant concentration
(A) product is no longer being formed.
(B) the reaction has reached equilibrium.
(C) all the catalytic sites are occupied.
(D) all the reactant has been consumed.
(B) PbCl2
(C) PbBr2
(D) PbI2
37. What is the standard cell potential for the reaction,
2Cr(s) + 3Sn2+(aq) -» 3Sn(s) + 2Cr3+(aq)
given the E° values shown?
Cr^aq) + 3e~
Cr(s) -0.744 V
Sn2+(aq) + 2e~ • Sn(s) -0.141 V
(A) 0.945V
(B) 0.603V
(C) -0.603V
(D) -0.945V
Not valid for use as an USNCO Olympiad National Exam after April 19, 2004.
PageS
38. How many electrons are needed in the balanced halfreaction for the oxidation of ethanol to acetic acid?
C2H5OH -* CH3COOH
(A) 1
(B) 2
(C) 3
(B) Cu2+(aq)
(C) H+(aq)
(D) Zn2+(aq)
(A) N
(C) 6.1 x 104
(D) 3.8 x 109
41. When an aqueous solution of potassium fluoride is
electrolyzed, which of the following occurs?
(A) O2 and H+ are produced at one electrode and H2 and
OH" are formed at the other.
(B) O2 and OH" are produced at one electrode and H2
and H+ are formed at the other.
(C) Metallic K is formed at one electrode and O2 and H+
are formed at the other.
(D) Metallic K is produced at one electrode and
elemental F2 is produced at the other.
42. A CuSO4 solution is electrolyzed for 20. minutes with a
current of 2.0 ampere. What is the maximum mass of
copper that could be deposited?
(A) 0.20 g
(B) 0.40 g
(C) 0.79 g
(D) 1.6g
43. Which experimental evidence most clearly supports the
suggestion that electrons have wave properties?
(A) diffraction
(A) 0
(D) deflection of cathode rays by a magnet
44. Which quantum number determines the number of
angular nodes in an atomic orbital?
(C) m,
(D) ms
45. Which element exhibits the greatest number of oxidation
states in its compounds?
(A) Ca
Page 6
(B) V
(C) 4
(D) 6
(B)
(Q
2 »F
(D)
49. According to the Lewis dot
: o : : :c :N :
structure shown, what are the
formal charges of the O, C and N atoms, respectively, in
the cyanate ion?
(A) 0,0,0
(B) -1,0,0
(C) -1,+1,
(D) +1,0,-2
50. The hybridization of As in AsF5 is best described as
(A) sp3
(B) sp4
(C) dsp3
(D) d2sp3
51. In which species do the atoms NOT lie in a single plane?
(A) BF3
(B) PF3
(C) C1F3
(D) XeF4
52. For which compound does the reaction,
MCO3(s)
MO(s) + CO2(g)
occur most readily?
(A) BeCO3
(B) MgCO3
(C) CaCO3
(D) BaCO3
53. The color of Co(H2O)62+ is best attributed to electronic
transitions
(A) between different n levels in the metal.
(B) between the metal's d orbitals.
(D) during ionization.
(C) photoelectric effect
(A) n
(B) 2
(C) from the Co2+ ion to water molecules.
(B) emission spectra
(B) 1
(D) CI
47. How many unpaired electrons are in a gaseous Fe2+ ion in
its ground state?
(A) >2 N
(B) 22
(C) S
48. Which species is most likely to lose a positron (|3+)?
40. The standard potential for the reaction
Cl2(g) + 2Br-(aq) ---> Br2(l) + 2Q-(aq)
is 0.283 volts. What is the equilibrium constant for this
reaction at 25 °C?
(A) 1 . 6 x l 0 5
(B) P
(D) 4
39. Which is the weakest oxidizing agent in a 1 M aqueous
solution?
(A) Ag+(aq)
46. Of the elements given, which has the lowest ionization
energy?
(C) Cu
54. When the carbon-oxygen bonds in the species; CH3OH,
CH2O and CHO2" are arranged in order of increasing
length, which is the correct order?
(A) CH3OH < CH2O < CHO2"
(B) CH2O < CH3OH < CHO2(C) CHO2- < CH3OH < CH2O
(D) CH2O < CHO2- < CH3OH
(D) As
Not valid for use as an USNCO Olympiad National Exam after April 19, 2004.
55. How many different trichlorobenzenes, C6H3C13, can be
formed?
(A) 1
(B) 2
(C) 3
(D) 4
56. What organic product is formed from the mild oxidation
of a secondary alcohol?
(A) acid
(B) aldehyde
(C) ether
(D) ketone
57. The compound with the formula, H2NCH2CH2COOH, is
best classified as a(n)
(A) amide
(B) amino acid
(C) fatty acid
(D) nucleic acid
58. The reaction between which pair of reactants occurs the
fastest for [OH'] = 0.010 M?
(A) CH3CH2CH2CH2C1 + OH~
(B) (CH3)3CC1 + OH(C) CH3CH2CH2CH2Br + OH~
(D) (CH3)3CBr + OH59. What is the major organic product formed from the
reaction of CH3CH-CH2 and HC1?
(A) CH3CHC1CH3
(B) CH3CH2CH2C1
(C) CH3CHC1CH2C1
(D) CH2C1CH=CH2
60. Fats and oils are formed from the combination of fatty
acids with what other compound?
(A) cholesterol
(B) glucose
(C) glycerol
(D) phenol
END OF TEST
Not valid for use as an USNCO Olympiad National Exam after April 19,2004.
Page 7