First Round SwissChO 2017
Important Informations
• This exam should be solved within approximately one hour, using only books and a calculator. The answers should be copied to the separate answer sheet using a dark felt tip
pen or ballpoint pen. You may not use a pencil.
• It is possible that more than one answer is correct.
• Following the IChO regulations, everybody is eligible to participate who:
– was born on July 1st 1997 or later,
– is not enrolled at a university,
– is or has been attending a Swiss school.
• Answer have to be submitted until October 30th 2016.
SwissChO 2017
Multiple Choice Exam
Exam Questions
1. What is the name of the process when an atom looses or gains an electron?
A. Ionization
B. Recombination
C. Disproportionation
D. Desublimation
E. Carbonization
2. Which of the following elements, in their most stable form, occurs as a liquid near room
temperature at atmospheric pressure?
A. F
B. Ga
C. Hg
D. P
E. C
3. Which of the following compounds are considered to be ionic?
A. HCl
B. K2 SiF6
C. CCl4
D. CaBr2
E. LiF
4. Which of the following ion or molecule pairs are strictly isoelectronic?
A. NO+ , CO
B. Cl2 , Se22 –
C. NO+ , C22 –
D. Cl2 , S22 –
E. CO2 , CS2
5. What is the oxidation state of nitrogen in the following compounds?
X: NH3
Y: NO2 •
Z: H2 NOH
A. X: +III ; Y: +IV ; Z: -I
B. X: +III ; Y: +V ; Z: +I
C. X: -III ; Y: -IV ; Z: -II
D. X: -III ; Y: +IV ; Z: -I
6. What is the number of H2 O in the following reaction?
Al2 C3 + X H2 O −−→ 4 Al(OH)3 + 3 CH4
A. 6
B. 3
C. 4
D. 24
E. 12
7. The complete combustion of ethane gives CO2 and H2 O. Find the correct, smallest whole
numbers for the following reaction in order to get the proper stochiometry:
2 C2 H6 + X O2 −−→ Y CO2 + Z H2 O
A. X=3 ; Y=2 ; Z=3
B. X=1 ; Y=1 ; Z=6
C. X=7 ; Y=4 ; Z=6
D. X=2 ; Y=4 ; Z=6
E. X=7 ; Y=6 ; Z=4
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SwissChO 2017
Multiple Choice Exam
8. Which are the conjugated bases of NH3 and HCO3 – ?
A. not available ; CO32 –
B. not available ; CO2
C. NH2 – ; CO32 –
D. NH2 – ; CO2
E. NH4+ ; CO2
9. Which of the following solutions is most acidic?
A. 1.0 mg HCl in 100 mL of water
B. 10 g of K2 CO3 in 1.0 L of water
C. 0.1 mol H3 PO4 and 0.5 mol NaH2 PO4 in 1.0 L of water
D. 1.0 mol of NaOH in 100 mL of water
10. One way to produce chlorine is with the following reaction:
−−
→
MnO (s) + 4 HCl(aq) −
←
− MnCl (aq) + Cl (g) + 2 H O
2
2
2
2
How many gramm HCl are required to have a complete reaction if 10 g MnO2 are used?
A. 40 g
B. 16.8 g
C. 2.5 g
D. 8.2 g
E. This is not possible to calculate with the provided data.
11. Lets stay at the reaction:
−−
→
MnO2 (s) + 4 HCl(aq) −
←
− MnCl2 (aq) + Cl2 (g) + 2 H2 O
To which side shifts the equlibrium if a) more MnO2 is used and b) if more pressure is
applied?
A. both to left
B. both to right
C. a) to left and b) to right
D. a) nothing happens and b) to left
E. a) to right and b) to left
12. At 25 ◦C, 1.7 × 10−5 mol/L Cd(OH)2 dissolve. Calculate the solubility product L.
A. L(Cd(OH)2 ) = 2.0 × 10−14 mol3 /L3
B. L(Cd(OH)2 ) = 2.0 × 10−14 mol/L
C. L(Cd(OH)2 ) = 4.9 × 10−15 mol3 /L3
D. L(Cd(OH)2 ) = 1.4 × 10−10 mol2 /L2
E. L(Cd(OH)2 ) = 4.9 × 10−15 mol/L
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SwissChO 2017
Multiple Choice Exam
13. According to VSEPR theory, which structure(s) have the following molecules?
X: SnH4 Y: SeF3 –
A. both planar
B. X: quadratic-planar ; Y: trigonal-pyramidal
C. X: tetraedral ; Y: planar
D. X: quadratic-planar ; Y: T-shaped
E. X: tetraedral ; Y: trigonal-pyramidal
14. For a reaction with ∆r H ◦ > 0 and ∆r S ◦ < 0 , which statement is correct?
A. The reaction occurs at high temperatures voluntarily.
B. The reaction occurs at low temperatures voluntarily.
C. There is no temperature at which the reaction proceeds voluntarily.
D. The reaction occurs at any temperature voluntarily.
E. The reaction is endothermic.
15. The chlorinating agent PCl5 can be prepared from PCl3 and chlorine:
PCl3 (g) + Cl2 (g) ←−→ PCl5 (g)
∆r H ◦ = −87.9 kJ/mol
∆r S ◦ = −170 J/(molK)
Assuming ∆r H ◦ and ∆r S ◦ to be constant, at which temperature will the reaction be in
equilibrium for standard pressure and concentrations?
A. 0 ◦C
B. 244 ◦C
C. 517 ◦C
D. 790 ◦C
16. What is the concentration of chlorophyll A in a plant extract in methanol, when you measure an extinction of E500 = 1.1934 at a wavelength of 500 nm? Chlorophyll A has an
extinction coefficient of "500 = 5967 cm−1 /M and the cuvette has a length of 1 cm.
A. 0.1 mM
B. 0.1 M
C. 0.1 M
D. 0.2 mM
E. 0.5 mM
17. Which of the following is most likely a reaction of order 0?
A. Reaction of oxygen with hydrogen to water initiated with a match
B. Ozone destruction by chlorine radicals in the stratosphere
C. Reactions on a Cobalt catalyst in a Fischer-Tropsch reaction (Coal liquidification)
D. Precipitation of Ag(Cl)) from a mixture of NaCl and AgNO3
18. The activation energy of a chemical reaction is Ea = 1 kJ/mol, what is the reaction rate at
a temperature of 298.15 K? (A= 0.1 mol/s)
A. k = 0.067
B. k = 0.067 mol/s
C. k = 0.0067 mol/s
D. k = 0.325 mol/s
E. k = 0.0067 mol2 /s2
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SwissChO 2017
Multiple Choice Exam
19. State the equation for the radioactive α-decay for
A.
B.
C.
D.
E.
210
Po
84
210
Po
84
210
Po
84
210
Po
84
210
Po
84
210
Po.
84
−−→ 206
Pb + 42He
82
−−→ 210
At + 01e –
85
−−→ 206
Pb + 2 01e –
82
−−→ 209
Bi + 11H
83
−−→ 214
Rn + 42He
86
20. Tritium 31T is an radioactive isotopes of hydrogen with an half-life of 12.32 years. It is of
great interest as a possible source for nuclear fusion as a new energy source. After which
time has 95 % of the initial number of nuclei in a tritium sample of 1 g decayed?
A. 0.91 days
B. 0.91 years
C. 53.2 years
D. 94.2 years
21. You mix 0.1 mol of oxygen with 0.5 mol of argon and then apply a pressure of 2 atm at
room temperature (25 ◦C). What is the volume of the mixture?
A. 7.3 dm3
B. 7.3 L
C. 3.6 L
D. 3.6 m3
E. 3.6 dm3
22. DNA chip fabrication requires a photocleavable protection group. The minimal photon
energy for activation is E ph = 4.73 × 10−19 J. What wavelengths of light will trigger the
photo reaction?
A. 532 nm and higher
B. 365 nm and lower
C. 420 nm and lower
D. 420 nm and higher
E. 532 nm and lower
23. The redox pairs Au3+ / Au and Tl3+ / Tl+ can undergo a redox reaction where Au3+ is
reduced and Tl+ gets oxidised:
W Au3+ + X Tl+ −−→ Y Au + Z Tl3+
What are the stoichiometric coefficient for this reaction?
A. W=1; X=1 ; Y=1 ; Z=1
B. W=1; X=2 ; Y=1 ; Z=2
C. W=2; X=3 ; Y=2 ; Z=3
D. W=3; X=2 ; Y=3 ; Z=2
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SwissChO 2017
Multiple Choice Exam
24. Automotive batteries are based on the comproportionation of lead and lead dioxide in
diluted sulphuric acid. What is the voltage of such a galvanic cell assuming standard
conditions?
E0 /V
Electrode
Half-cell reaction
Kathode
Anode
PbO2 + SO42 – + 4H+ + 2e – −−→ PbSO4 + 2H2 O
PbSO4 + 2e – −−→ Pb + SO42 –
A. 1.33 V
B. 2.05 V
C. 2.66 V
25. What is the correct name of the following compound?
[Fe(NH3 )6 ][Cr(CN)6 ]
A. Hexaamineironate(II)hexacyanochrome(III)
B. Hexaamineiron(III)hexacyanochromate(III)
C. Hexacyanochromate(II)hexaamineiron(II)
D. Hexaamineiron(III)hexacyanidochromate(III)
E. Hexacyanoiron(III)hexaaminechromate(III)
26. How many Isomers of the following complexes do exist?
X: [Pt(NH3 )2 Cl2 ]
Y: [Pt(NH3 )3 Cl3 ]Cl
A. X: 2 ; Y: 6
B. X: 3 ; Y: 4
C. X: 2 ; Y: 2
D. X: 1 ; Y: 2
E. X: 2 ; Y: 0
27. How is the following structure called?
A. (E)-3-(4-Chlorphenyl)propenal
B. (Z)-4-(3-Propenal)benzylchloride
C. (E)-4-(3-Propanon)phenylchloride
D. (Z)-3-(4-Chlorphenyl)propanon
E. (E)-3-(4-Chlorbenzyl)propenon
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1.69
−0.36
D. 4.10 V
SwissChO 2017
Multiple Choice Exam
28. What is the hybridisation of the carbon atom in the following molecules?
X: CH3+
Y: CO2
Z: H2 CO3
A. X :Sp3 ; Y: Sp ; Z: Sp3
B. X: Sp ; Y: Sp2 ; Z: Sp3
C. X: Sp2 ; Y: Sp3 ; Z: Sp
D. X: Sp ; Y: Sp2 ; Z: Sp2
E. X: Sp2 ; Y: Sp ; Z: Sp2
29. Are the following molecules aromatic, anti-aromatic or non-aromatic?
A. X: Aromatic; Y: Non-aromatic ; Z: Aromatic
B. X: Anti-aromatic ; Y: Aromatic ; Z: Anti-aromatic
C. X: Non-aromatic; Y: Aromatic ; Z: Non-aromatic
D. X: Anti-aromatic ; Y: Non-aromatic ; Z: Aromatic
E. X: Aromatic; Y: Aromatic ; Z: Aromatic
30. Which of the following coloured protons is the most acidic? (From left to right: red, green,
blue, turquise.)
A. The red proton
B. The blue proton
C. The turquise proton
D. The green proton
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SwissChO 2017
Multiple Choice Exam
31. What is the main product of the following reaction?
32. What is the main product of the following reaction?
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SwissChO 2017
Multiple Choice Exam
Questions without any influence on the result
33. How did you come to know about the Swiss Chemistry Olympiad?
A. Teacher
B. Colleagues
C. Press
D. Others
34. Would you take part at the Central Exam in January 2017 in case you qualify?
A. Yes
B. No
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