Prepared by the American Chemical Society Chemistry Olympiad Examinations Task Force
OLYMPIAD EXAMINATIONS TASK FORCE
Arden P. Zipp, Chair, State University of New York, Cortland, NY (deceased)
James Ayers, Mesa State College, Grand Junction, CO
Mark DeCamp, University of Michigan, Dearborn, MI
Marian DeWane, Centennial High School, Boise, ID
Xu Duan, Holton-Arms School, Bethesda, MD
Valerie Ferguson, Moore High School, Moore, OK
Julie Furstenau, Thomas B. Doherty High School, Colorado Springs, CO
Kimberly Gardner, United States Air Force Academy, CO
Paul Groves, South Pasadena High School, South Pasadena, CA
Preston Hayes, Glenbrook South High School, Glenbrook, IL (retired)
Adele Mouakad, St. John’s School, San Juan, PR (retired)
Jane Nagurney, Scranton Preparatory School, Scranton, PA
Ronald Ragsdale, University of Utah, Salt Lake City, UT
DIRECTIONS TO THE EXAMINER
This test is designed to be taken with an answer sheet on which the student records his or her responses. All answers are to be marked on that sheet, not written in the booklet. Each student should be provided with an answer sheet and scratch paper, both of which must be turned in with the test booklet at the end of the examination. Local Sections may use an answer sheet of their own choice.
The full examination consists of 60 multiple-choice questions representing a fairly wide range of difficulty. Students should be permitted to use non-programmable calculators. A periodic table and other useful information are provided on page two of this exam booklet for student reference.
Suggested Time: 60 questions—110 minutes
DIRECTIONS TO THE EXAMINEE
DO NOT TURN THE PAGE UNTIL DIRECTED TO DO SO.
This is a multiple-choice examination with four choices for each question. There is only one correct or best answer to each question. When you select your choice, blacken the corresponding space on the answer sheet with your pencil. Make a heavy full mark, but no stray marks. If you decide to change your answer, be certain to erase your original answer completely.
ABBREVIATION | SYMBOL | ABBREVIATION | SYM. | ABBREVIATION | SYM. | CONSTANTS |
amount of substance |
n | Faraday constant | F | molar mass | M | R = 8.314 J•mol–1•K–1 |
ampere | A | free energy | G | mole | mol | R = 0.0821 L•atm•mol–1•K–1 |
atmosphere | atm | frequency | ν | Planck’s constant | h | 1 F = 96,500 C•mol–1 |
atomic mass unit | u | gas constant | R | pressure | p | NA = 6.022 * 1023 mol–1 |
Avogadro constant | NA | gram | g | rate constant | k | h = 6.626 * 10–34 J•s |
Celsius temperature | oC | hour | h | reaction quotient | Q | c = 2.998 * 108 m•s–1 |
centi– prefix | c | joule | J | second | s | 0 °C = 273.15 K |
coulomb | C | kelvin | K | speed of light | c | 1 atm = 760 mm Hg |
density | d | kilo– prefix | k | temperature | T,K | |
electromotive force | E | liter | L | time | t | |
energy of activation | Ea | measure of pressure |
mmHg | vapor pressure | VP | |
enthalpy | H | milli– prefix | m | volt | V | |
entropy | S | molal | m | Volume | V | |
equilibrium constant | K | molar | M |
2014 U.S. NATIONAL CHEMISTRY OLYMPIAD LOCAL SECTION EXAM
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Question 1 of 57
1. Question
Which compound contains the highest percentage of magnesium by mass?
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Question 2 of 57
2. Question
In the diagram above the paired open spheres represent H2 molecules and the paired solid spheres represent N2 molecules. When the molecules in the box react to form the maximum possible amount of ammonia (NH3) molecules, what is the limiting reactant and how many molecules of NH3 can be formed?
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Question 3 of 57
3. Question
Vanillin, C8H8O3 (M = 152 g/mol), is the molecule responsible for the vanilla flavor in food. How many oxygen atoms are present in a 45.0 mg sample of
vanillin?Correct
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Question 4 of 57
4. Question
The solubility of K2Cr2O7 in water is 125 g/L at 20 °C. A solution is prepared at 20 °C that contains 6.0 grams of K2Cr2O7 in 50. mL of water. This solution is
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Question 5 of 57
5. Question
What is the molarity of sodium ions in a solution prepared by diluting 250. mL of 0.550 M Na2SO4 to 1.25 L?
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Question 6 of 57
6. Question
Which of the following is a weak electrolyte in aqueous solution?
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Question 7 of 57
7. Question
Which list gives nonmetals that are found in their elemental forms in nature?
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Question 8 of 57
8. Question
Which one of the following cannot act as an oxidizing agent?
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Question 9 of 57
9. Question
Which substance is the primary component in stalactites and stalagmites in caves?
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Question 10 of 57
10. Question
Five successive determinations of the density of an alloy gave the following results: 10.29 g/mL, 9.95 g/mL, 10.06 g/mL, 9.89 g/mL, 10.18 g/mL
What value should be reported for the density of this alloy?Correct
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Question 11 of 57
11. Question
A student is asked to analyze a water sample from a stream for total solids (TS), dissolved solids (DS), and suspended solids (SS). She carries out the experiments below.
1. A 25-mL portion of the water sample is evaporated to dryness in a pre-weighed evaporating dish to give mass 1.
2. A separate 25-mL portion is filtered into a second preweighed evaporating dish and evaporated to dryness to give mass 2.
How are values for TS, SS and DS (per 25 mL water) determined?
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Question 12 of 57
12. Question
Which method(s) can be used to determine the concentration of HNO3 in an aqueous solution of nitric acid?
I titration with a standard base
II titration with a standard oxidizing agent
III precipitation with Ag+Correct
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Question 13 of 57
13. Question
The kinetic theory of gases assumes all of the following EXCEPT:
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Question 14 of 57
14. Question
A sample of He gas in a flexible container at room temperature exhibits a certain pressure. What will be the new pressure when the absolute temperature and volume of the container are both halved? The pressure of the He will be
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Question 15 of 57
15. Question
The molecules in a sample of pure liquid dichloromethane, CH2Cl2, experience which of the following intermolecular forces?
I dispersion forces
II dipole-dipole forces
III hydrogen bondingCorrect
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Question 16 of 57
16. Question
Which property best distinguishes metals from other types of solids?
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Question 17 of 57
17. Question
What type of solid is silicon carbide, SiC?
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Question 18 of 57
18. Question
The normal boiling point and vapor pressure at 25 °C are measured for liquids in two flasks. Flask A contains pure water and flask B contains a 1.0 M aqueous NaCl solution. Which flask contains the liquid with the higher boiling point? Which flask contains the liquid with the higher vapor pressure?
Higher boiling point Higher vapor pressure
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Question 19 of 57
19. Question
Given chemical equations for these reactions
S(s) + O2(g) → SO2(g) ΔH˚= –296.8 kJ•mol–1
H2(g) + ½ O2(g) → H2O(l) ΔH˚= –285.8 kJ•mol–1
H2(g) + S(s) → H2S(g) ΔH˚= –20.6 kJ•mol–1What is the value of ΔH for the reaction below?
2 H2S(g) + 3 O2(g) → 2 H2O(l) + 2 SO2(g)Correct
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Question 20 of 57
20. Question
Consider the following reactions
I 2 NO2(g) → N2(g) + 2 O2(g)
II 2 IBr(g) → I2(s) + Br2(l)For which reaction is ΔS° < 0?
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Question 21 of 57
21. Question
Calculate the energy released by the reaction
4 Fe(s) + 3 O2(g) → 2 Fe2O3(s)
when a 55.8 g sample of iron reacts completely with 1.00 mole of oxygen. The enthalpy of formation (ΔHf˚) of Fe2O3(s) is –826 kJ•mol–1.Correct
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Question 22 of 57
22. Question
The specific heat capacities of three metals are given below.
Metal Fe Pb Zn Specific heat, J•g–1•°C–1 0.470 0.130 0.388 If 1.00 g of each metal is heated to 100 °C and added to 10.0 g of H2O at 25.0 °C, what is the order of the temperatures of the final mixtures from the lowest to the highest?
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Question 23 of 57
23. Question
The enthalpy of formation, ΔHf˚, equals zero at 25 °C for which of the following in their standard states?
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Question 24 of 57
24. Question
Liquid water is injected into an oven at 400 K. What are
the signs for ΔG, ΔH, and ΔS for the physical
transformation that occurs?ΔG ΔH ΔS (A) + – – (B) + – 0 (C) – + + (D) – + 0 Correct
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Question 25 of 57
25. Question
C(s) + CO2(g) → 2 CO(g) ΔH = 172 kJ•mol–1
In a suitable reaction vessel, pieces of graphite are mixed
with carbon dioxide gas at 1.00 atm and 1000 K. Which
of the following changes will result in an increase in
reaction rate?Correct
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Question 26 of 57
26. Question
The reaction CH3NC → CH3CN is first order. Which
reaction characteristic changes as the reaction proceeds?Correct
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Question 27 of 57
27. Question
A(g) + B(g) → C(g)
The data below were obtained for the reaction between A and B. What is the rate law for this reaction?Trial [A]0 (mol•L–1) [B]0 (mol•L–1) Initial Rate of
Reaction
(mol•L–1• s–1)1 0,10 0,10 6.5 × 10–5 2 0,20 0,10 2.6 × 10–4 3 0,10 0,20 6.5 × 10–5 Correct
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Question 28 of 57
28. Question
A first-order reaction is carried out at several different temperatures. The data are plotted as ln k vs 1/T. How is the slope of the graph related to Ea?
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Question 29 of 57
29. Question
Which statement about the behavior of a catalyst is correct?
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Question 30 of 57
30. Question
An endothermic reaction has a positive value for ΔS. Which of the following is true about the equilibrium constant for this reaction?
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Question 31 of 57
31. Question
Phosphoric acid, H3PO4, establishes the following
equilibria in aqueous solution.
H3PO4(aq) + H2O(l) H3O+(aq) + H2PO4– (aq) K1
H2PO4–(aq) + H2O(l) H3O+(aq) + HPO42–(aq) K2
HPO42–(aq) + H2O(l) H3O+(aq) + PO43–(aq) K3What is the relationship among the K values?
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Question 32 of 57
32. Question
Which pair of solutes could be used to prepare an aqueous buffer solution with a pH < 7?
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Question 33 of 57
33. Question
What will be the result when 15.0 mL of 0.040 M lead(II) nitrate is mixed with 15.0 mL of 0.040 M sodium chloride?
PbCl2(s) Pb2+(aq) + 2 Cl–(aq) [Ksp = 1.7 × 10–5]
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Question 34 of 57
34. Question
What is the oxidation number of As in the compound K(NH4)2AsO4•6H2O?
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Question 35 of 57
35. Question
When the equation
__ MnO4–+ __ SO32–+ __ H+ → __ Mn2+ + __ SO42–+__ H2O
is balanced correctly with the smallest whole number coefficients, what is the coefficient for H2O?
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Question 36 of 57
36. Question
Half-Reaction E° (V) 2 H+ + 2 e– → H2 0.00 Pd2+ + 2 e– → Pd 0.90 O2 + 4 H+ + 4 e– → 2 H2O 1.23 According to the equations and data in the table above, which species is the strongest reducing agent of the following choices?
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Question 37 of 57
37. Question
Half-Reaction E° (V) Zn2+(aq) + 2 e–→ Zn(s) –0.76 Cr3+(aq) + 3 e–→ Cr(s) –0.744 Fe2+(aq) + 2 e–→ Fe(s) –0.409 Use the E° values in the table above to determine which of the following reactions will give the highest potential in a voltaic cell.
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Question 38 of 57
38. Question
The cell potential for the voltaic cell depicted below is 0.109 V under standard conditions, 1M Ni2+(aq) and 1 M Pb2+(aq).
Which change will increase the voltage?
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Question 39 of 57
39. Question
Aluminum is produced commercially by the electrolysis of Al2O3. How many hours would be required to produce 250. g of Al using a 5.00 Ampere current?
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Question 40 of 57
40. Question
A sulfur atom in its ground state has the electron configuration
1s2 2s2 2p6 3s2 3p4
How many orbitals are occupied by at least one electron?
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Question 41 of 57
41. Question
For which of the following transitions would a hydrogen atom absorb a photon with longest wavelength?
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Question 42 of 57
42. Question
Which set of quantum numbers is not possible?
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Question 43 of 57
43. Question
What property of the oxygen atom is represented by the equation O(g) + e– → O–(g)?
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Question 44 of 57
44. Question
Which of the following isoelectronic species has the largest radius?
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Question 45 of 57
45. Question
Which group best illustrates the transition from nonmetallic to metallic behavior with increasing atomic number?
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Question 46 of 57
46. Question
Which atom is least likely to violate the octet rule in its compounds?
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Question 47 of 57
47. Question
In the Lewis structure for formic acid, HCOOH, how many bonding pairs and lone pairs of electrons are present?
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Question 48 of 57
48. Question
Which ionic compound has the largest lattice energy?
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Question 49 of 57
49. Question
When 1.0 mole of H2O2 decomposes to form H2O and O2, 103 kJ of energy is released. Given the bond energies below, what is the bond energy of the O–O single bond in H2O2?
Bond H-O O=O Bond Energy, kJ•mol–1 463 498 Correct
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Question 50 of 57
50. Question
Which species has a different number of pi bonds than the others?
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Question 51 of 57
51. Question
Which molecule is correctly matched with its shape as predicted by VSEPR theory?
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Question 52 of 57
52. Question
Which of the following statements regarding structural isomers is correct? They have
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Question 53 of 57
53. Question
What is the IUPAC name for the compound CH3CH2CH2CH2CHO?
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Question 54 of 57
54. Question
Which compound will react rapidly with Br2?
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Question 55 of 57
55. Question
The reaction below is best classified as
CH3OH + HCOOH → HCOOCH3 + H2O (acid catalizator is present – H+ )
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Question 56 of 57
56. Question
Which element is not found in common amino acids?
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Question 57 of 57
57. Question
Which of the following is not classified as a carbohydrate?
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Leaderboard: 2014 U.S. NATIONAL CHEMISTRY OLYMPIAD LOCAL SECTION EXAM
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