Team: ___________________________________
_______
/ 100
Answer Sheet
(Only answers placed on this sheet will be graded for this part)
(Tiebreaker #1 is the total score on Multiple Choice)
1.) ________
16.) ________
31.) ________
46.) ________
2.) ________
17.) ________
32.) ________
47.) ________
3.) ________
18.) ________
33.) ________
48.) ________
4.) ________
19.) ________
34.) ________
49.) ________
5.) ________
20.) ________
35.) ________
50.) ________
6.) ________
21.) ________
36.) ________
51.) ________
7.) ________
22.) ________
37.) ________
52.) ________
8.) ________
23.) ________
38.) ________
53.) ________
9.) ________
24.) ________
39.) ________
54.) ________
10.) ________
25.) ________
40.) ________
55.) ________
11.) ________
26.) ________
41.) ________
56.) ________
12.) ________
27.) ________
42.) ________
57.) ________
13.) ________
28.) ________
43.) ________
58.) ________
14.) ________
29.) ________
44.) ________
59.) ________
15.) ________
30.) ________
45.) ________
60.) ________
Chemistry Lab Multiple Choice
I. Gases
1. Hydrogen peroxide decomposes into H2O(l) and O2(g). What volume of O2 is collected at
27.0°C and 740. torr if only half the 130g of hydrogen peroxide decompose? (Ignore presence of
water vapor)
(A) 4.0 L (B) 24.1 L (C) 45.6 L (D) 48.3 L
2. A solution of BaF2 which has a density of 4.89 g/mL is 20% barium ions by mass. What is the
moles of fluoride ions in 150 mL of solution?
(A) 2.14 mol (B) 4.35 mol (C) 5.67 mol (D) 8.02 mol
3. A sealed flask which is 22.4 L contains an ideal gas at STP. How many moles of gas are
contained?
(A) 0.20 mol (B) 0.50 mol (C) 1.00 mol (D) 2.00 mol
4. There are two balloons sitting on a lab bench under the same conditions. One contains 6.0 g of
H2(g) while the other 96 g of O2(g). How do the two balloons compare?
(A) The balloons have the same volume.
(B) The H2 balloon has a volume 16 times the O2 balloon.
(C) The O2 balloon has a volume 16 times the H2 balloon.
(D) The H2 balloon has half the volume of the O2 balloon.
5. A 0.150 L sample of gaseous hydrocarbon has a density of 0.582 g/L at 76°C and 790 torr.
What is its formula?
(A) CH4 (B) C5H12 (C) C10H22 (D) C15H32
6. An equimolar mixture of C2H6 and C5H12 diffuses through a pinhole. What is ratio of
C2H6/C5H12 that escapes?
(A) 0.645/1 (B) 1.290/1 (C) 1.55/1 (D) 2.4/1
7. The Kinetic molecular theory describes the behavior of ideal gases. Real gases deviate from
these postulates. Under what conditions do real gases deviate most from the theory?
(A) low P, low T (B) low P, high T (C) high P, low T (D) high P, high T
8. An apparatus contains Br2(g) in a solution. What happens to vapor pressure when the piston
lowers and decreases the volume of Br2(g) above the solution by half? (Assume no temperature
change).
(A) The vapor pressure is zero.
(B) The vapor pressure is half of the original.
(C) The vapor pressure is 2 times the original.
(D) The vapor pressure did not change.
9. What is the average velocity of H2 molecules at 60 K relative to their velocity at 120 K?
(A) 0.50 times the velocity at 120 K (B) 0.71 times the velocity at 120 K (C) 1.41 times the
velocity at 120 K (D) 2.00 times velocity at 120 K
10. 0.100L of N2(g) takes 220s to completely diffuse through a pinhole. Under the same
temperature and pressure, 0.100 L of unknown gas takes 300s to completely diffuse through the
same pinhole. What is the molar mass of the unknown gas?
(A) 0.733 g/mol (B) 1.36 g/mol (C) 26.0 g/mol (D) 52.1 g/mol
11. What is the total pressure in a 2.00 L container that holds 1.00 g H2, 2.00 g He, and 16.0 g of
CO at 26.0°C?
(A) 19.2 atm (B) 21.3 atm (C) 26.1 atm (D) 30.5 atm
12. Hydrogen gas is collected over water at 43°C and 740 mmHg. Water has a vapor pressure of
65 mmHg at 43°C. If 250 mL of hydrogen gas is collected, what portion of the volume is the dry
form of this gas under the same temperature and pressure?
(A) 310 L (B) 228 L (C) 250 L (D) 332 L
13. A sealed flask contains an ideal gas. The 15 L flask is initially at 100 K and 20 atm. When
the flask is heated, it reaches a pressure of 300 atm. What is its final temperature?
(A) 1500 K (B) 1300 K (C) 1000 K (D) 887 K
14. A container contains equal amounts by mass of gaseous O2, H2O, and CO2 for a total
pressure of 3 atm. How do the partial pressures of gaseous O2, H2O, and CO2 compare?
(A) 𝑃!! ! = 𝑃!! = 𝑃!"!
(B) 𝑃!! ! = 𝑃!! < 𝑃!"!
(C) 𝑃!! ! < 𝑃!! < 𝑃!"!
(D) 𝑃!! ! > 𝑃!! > 𝑃!"!
15. 2.00 g of water is introduced to a 4.00 L evacuated flask at 298 K. The vapor of water at 298
K is 83.8 torr. What is the mass of liquid water when equilibrium was reached?
(A) 2.00 g (B) 1.67 g (C) 1.33 g (D) 1.00 g
16. Gaseous SO2 does not behave exactly like an ideal gas. Its collisions are not perfectly elastic.
Using the ideal gas equation, a student obtains the pressure of a sample of SO2(g). How does the
actual pressure of the sample deviate?
(A) The pressure is less than predicted by ideal gas equation because of attractive/repulsive
forces between molecules.
(B) The pressure is more than predicted by ideal gas equation because of the volume of the
molecules.
(C) The pressure is less than predicted by ideal gas equation because of the mass of the
molecules.
(D) The pressure does not deviate at all.
17. Approximately how many times faster will a molecule of hydrogen gas effuse than an atom
of radon?
(A) 1 times the rate of radon
(B) 5 times the rate of radon
(C) 10 times the rate of radon
(D) 100 times the rate of radon
18. What is special about liquid water compared to other substances of similar molar masses?
1. Low boiling point
2. High melting point
3. Large specific heat capacity
4. Large surface tension
(A) 2 only (B) 3 only (C) 2,3, and 4 (D) 1, 2, 3, and 4
19. What does liquid CH2N2 need to overcome to evaporate?
I.
Van der Waals forces
II.
Dipole-dipole forces
III.
Attractive forces with air
(A) I only (B) II only (C) I and II (D) I, II, and III
Questions 20, 21, and 22 are related.
20. When potassium nitrate decomposes, a gaseous product is formed. The gaseous product is
collected in 2.0 L. It has a pressure of 1.6 atm and temperature of 306 K. How many moles of
gaseous product is formed?
(A) 0.127 mol (B) 0.150 mol (C) 0.254 mol (D) 0.312 mol
21. How many grams of potassium nitrate is needed for the decomposition above?
(A) 12.9 g (B) 21.7 g (C) 25.7 g (D) 34.5 g
22. The effusion rate of argon under identical conditions is 25.4 mL/min. What is the effusion
rate of the gaseous product?
(A) 25.4 mL/min (B) 28.4 mL/min (C) 30.4 mL/min (D) 37.2 mL/min
23. In 2.0 L container, a sample of natural gas contains only methane and ethane. The mole ratio
of methane is 0.877. What is the partial pressure of ethane at 1.5 atm and 22°C?
(A) 0.005 atm (B) 0.111 atm (C) 0.123 atm (D) 0.185 atm
24. Which of the pure substances have the highest normal boiling point?
(A)PH3 (B) CH4 (C) H2O (D) NH3
25. The kinetic energy of the molecules in a sample of water in its stable state at 1 atm and -8°C
doubles. What are the initial and final phases?
(A) solid → solid (B) solid → gas (C) liquid → gas (D) liquid → solid
26. What is the change in volume when 20.0g carbon dioxide sublimes at 25°C in a pistol at 1.0
atm? (Neglect volume of solid CO2)
(A) 8.3 L (B) 9.4 L (C) 10.1 L (D) 11.1 L
27. The reaction between iron and hydrochloric acid is Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g).
How many kilograms of iron was needed to produce 2000. L of H2 at 2.5 atm and 52°C? (Ignore
the vapor pressure of HCl and FeCl2)
(A) 5.34 kg (B) 10.46 kg (C) 13.21 kg (D) 18.71 kg
28. Acetone and benzene form an ideal solution when mixed. Acetone has a vapor pressure of
214 torr at 25°C and benzene has a vapor pressure of 96 torr at 25°C. What is the vapor pressure
of the solution with equal amounts by moles of acetone and benzene (the mole fraction of both is
0.5)?
(A) lower than 96 torr (B) between 96 and 214 torr (C) exactly 214 torr (D) greater than 214 torr
29. Which physical property increases when intermolecular forces increase?
i.
boiling point
ii.
surface tension
iii.
viscosity
(A) i only (B) ii only (C) i and ii (D) i, ii, and iii
30. Which of the following laws do not relate to forming the ideal gas equation?
(A) Birch’s Law
(B) Charles’s Law
(C) Gay-Lussac’s Law
(D) Boyle’s Law
II. Thermodynamics
31. A bomb calorimeter contains 150. g of water. The calorimeter has a heat capacity of 567
J·°C-1 and water has a specific heat of 4.184 J·g-1·°C-1. How much heat, in kilojoules, is evolved
when temperature of the system increases from 24.54°C to 27.01°C?
(A) 2.95 kJ (B) 5.55 kJ (C) 7.48 kJ (D) 15.5 kJ
32. Consider this reaction and the enthalpy value.
H2(g) + ½ O2(g) → H2O(l)
ΔH°f = -286 kJ/mol
Which of the following statements is incorrect?
(A) The decomposition of water has a ΔH° of +286 kJ/mol.
(B) 286 kJ/mol of heat is released when 1 mol of H2O(l) is formed.
(C) The enthalpy of formation for H2O(g) is -286 kJ/mol.
(D) None of the above
33. Calculate the enthalpy of reaction when 2.0 g of S react with 5.0 g of O2.
S(s) + O2(g) → SO2(g) ∆H˚f = -296.8 kJ/mol
(A) -18.55 kJ (B) -39.0 kJ (C) -110.6 kJ (D) -296.8 kJ
34. A process that is exothermic and nonspontaneous could be the following:
(A) ΔH < 0, ΔS > 0, very high T
(B) ΔH < 0, ΔS < 0, very high T
(C) ΔH > 0, ΔS > 0, very high T
(D) ΔH > 0, ΔS < 0, very high T
35. Gibbs free energy, ΔG, is the free energy of the system used to do work. The sign of ΔG
determines the favorability of a reaction. For which reaction will ΔG decrease the most when
temperature of the system decreases from 32 °C to 0 °C?
(A) ΔH° = 45 kJ/mol, ΔS° = 45 J/mol-K
(B) ΔH° = 70 kJ/mol, ΔS° = 20 J/mol-K
(C) ΔH° = -45 kJ/mol, ΔS° = -45 J/mol-K
(D) ΔH° = -70 kJ/mol, ΔS° = -20 J/mol-K
36. Consider the balanced reaction:
4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g) ΔH° =-904.4 kJ
Calculate ΔH°f of NO(g) in kJ/mol. (ΔH°f for NH3 = -46.2 kJ/mol, ΔH°f for H2O(g) = -241.8
kJ/mol)
(A) 400.0 kJ/mol (B) 310.6 kJ/mol (C) 270.3 kJ/mol (D) 90.4 kJ/mol
37. Calculate the ΔH°rxn for the following ΔH°f values: H2O(l) = -285.8 kJ/mol, CH4 = -74.8
kJ/mol, CO(g) = -110.5 kJ/mol
H2O(l) + CH4 → CO(g) + 3H2(g)
(A) 210.4 kJ (B) 250.1 kJ (C) 260.7 kJ (D) 290.6 kJ
38. 30.0 mL of 0.100 M HNO3 titrates 30.0mL of 0.100 M KOH. The temperature of solution
rises by 2.0°C. What is the enthalpy of neutralization per mole of HNO3? (CP = 4.18 J·g-1·°C-1,
density = 1.0 g/mL-1)
(A) -5.0 kJ (B) -10.0 kJ (C) -87.7 kJ (D) -99.1 kJ
39. Which of the following substance has the highest entropy value, S˚, at 25 ˚C?
(A) NO2(g) (B) NO2(s) (C) NO2(aq) (D) They all have the same entropy value
40. For the reaction, CaCO3(s) → CO2(g) + CaO(s), which of the following is not always true?
(A) The entropy of the system is positive.
(B) The reaction is the decomposition of CaCO3.
(C) The reaction is spontaneous.
(D) Bonds of CaCO3 were broken for the formation of the products.
41. The combustion of 92g of liquid C2H5OH produces CO2(g) + H2O(l). What is the enthalpy
of combustion for C2H5OH(l)? (ΔH°f for H2O(l)) = -285.8 kJ/mol, ΔH°f for CO2(g) = -393.5 k
J/mol, ΔH°f for C2H5OH(l) = -277.7 kJ/mol)
(A) -1.2 × 10! (B) -2.7× 10! (C) -5.6 × 10! (D) -10.6 × 10!
42. The reaction 2SO2(g) → S2O4(g) has a ∆H < 0. For the reaction to be spontaneous, which of
the conditions must be true?
(A) ∆S > 0 (B) ∆G = 0 (C) ∆S = 0 (D) ∆G < 0
43. For which reaction is ∆H is closest to ∆E (internal energy)?
(A) 2Li(s) + F2(g) → 2LiCl(g)
(B) 3S(g) + 2 O3(g) → 3SO2(g)
(C) CO2(s) → CO2(g)
(D) Br2(g) + Cl2(g) → 2BrCl(g)
44. What is the relationship between S˚ and temperature?
(A) S˚ is more positive at high temperatures.
(B) S˚ is more positive at low temperatures.
(C) S˚ is less positive at high temperatures.
(D) S˚ is zero at high temperatures.
45. For the reaction at 25°C, 2C2H6(l) + 7O2(g) → 4CO2(g) + 6H2O(g), what expression gives
the ∆H?
Molar bond enthalpies
(kJ/mol)
C-H
413
H-O
465
C=O
532
O=O
498
(A) -0.73 × 10! kJ (B) -0.98 × 10! kJ (C) -1.4 × 10! kJ (D) -1.7× 10! kJ
46. You dissolve 6.98 g NaCl in 150 g of water at room temperature (25°C). Find the final
temperature of the solution. (Molar mass NaCl = 58.44 g/mol, ∆Hsoln/NaCl = 21.2 kJ/mol, CP, solution
= 4.184 J·g-1·°C-1)
(A) 21°C (B) 45°C (C) 67°C (D) 103°C
47. Benzene boils at 80.1°C with ∆H°vap = 30.77 kJ/mol. What is the ∆S°vap in J·mol-1 ·K-1?
(A) 87.1 (B) 76.9 (C) 38.4 (D) 20.8
48. In a bomb calorimeter, what thermodynamic quantity is used to measure heat of reaction?
(A) ∆H (B) ∆E (C) ∆S (D) ∆G
49. The specific heat of Ni is 0.440 J·g-1·°C-1 and the specific heat of water is 4.184 J·g-1·°C-1. If
90.7 g of nickel at 110°C is dissolved in 106.4 g of water at 27°C, what is the final temperature
of the system?
(A) 11.0°C (B) 18.8°C (C) 26.4°C (D) 33.8°C
50. 12 g of unknown metal heated at 75.0˚C is placed in 0.100 L water at 21.0˚C. When the
system has reached equilibrium, the final temperature of the system is 22.4˚C. Based on the
specific heat of the metal, find its identity?
(A) Ag (CP, 0.236 J/g ˚C)
(B) Cu (CP, 0.385 J/g ˚C)
(C) Fe (CP, 0.449 J/g ˚C)
(D) Al (CP, 0.901 J/g ˚C)
51. Determine the molar bond enthalpy for the reaction, H2 + Cl2 → 2HCl.
Molar bond enthalpies
(kJ/mol)
H-Cl
431
H-H
435
Cl-Cl
243
(A) -92 kJ (B) -184 kJ (C) -243 kJ (D) -431 kJ
52. Calculate ∆H˚f for the reaction: Zn(s) + H2S(g) → H2(g) + ZnS(s)
(∆H˚f for H2S = -20.6 kJ/mol, ∆H˚f for ZnS = -206.0 kJ/mol)
(A) -105.4 kJ (B) -146.6 kJ (C) -185.4 kJ (D) -226 kJ
53. Use bond energies and ∆H˚rxn to estimate the molar bond energy for C-Br:
CF4 + 2 Br2 → CBr4 + 2 F2 ∆H˚rxn = 892 kJ
Bond energies at 25˚C,
kJ/mol
C-F
440
Br-Br
193
F-F
159
(A) 234 kJ/mol (B) 393 kJ/mol (C) 427 kJ/mol (D) 674 kJ/mol
54. At 1 atm, which is the correct relationship for this equation:
C(s) + 2S(s) → CS2(g) ∆H˚ =92kJ
(A) ∆Erxn > ∆Hrxn
(B) ∆Erxn < ∆Hrxn
(C) ∆Erxn = ∆Hrxn + ∆Srxn
(D) ∆Erxn = ∆Hrxn – ∆Srxn
55. At standard pressure, if enthalpy is positive, what temperature is needed for this reaction to
be spontaneous?
(A) Low (B) High (C) Zero (D) All T
56. A 3.0 L container is filled with gas. The external pressure, outside the container, is 0.80 bar.
If the energy change is 500J, how much heat is the surroundings giving the container? (100 J = 1
L-bar)
(A) 502 J (B) 740 J (C) 800 J (D) 950 J
57. Which statement about phase diagrams is correct?
(A) The point in which the three phases (solid, liquid, gas) meets varies with temperature and
pressure.
(B) The substance has the same density in all three phases (solid, liquid, gas).
(C) The border between two phases is in equilibrium.
(D) The substance is never in equilibrium.
58. Ethane melts at 90.0 K and its enthalpy of fusion is 2.85 kJ/mol. What is the entropy of
fusion(J/mol-K) for ethane?
(A)15.3 (B) 21.0 (C) 29.8 (D) 31.7
59. How many kilojoules of energy is needed to melt 25g of ice at 0°C into liquid water at 21°C?
(ΔH°fusion for H2O is 333.5 kJ/kg and CP, liquid is 4.18 J·g-1·°C -1)
(A) 8.62 kJ (B) 10.53 (C) 13.56 (D) 23.30
60. What is the second law of thermodynamics?
(A) Energy is always conserved.
(B) There is a tendency for an isolated system to be more disordered.
(C) Energy can be lost as heat.
(D) Reaching absolute zero is impossible