Chem Final 40-66
54. For which acid is the value of the acid-dissociation constant, K, the smallest?
A- Acid 1
46. The experimental apparatus represented above is used to demonstrate the rates at which gases diffuse. When the cotton balls are placed in the ends of a tube at the same time, the gases diffuse from each end and meet somewhere in between, where they react to form a white solid. Which of the following combinations will produce a solid closest to the counter of the tube?
A- HCl and CH3NH2
53. Based on the data tables above, which of the following statements provides the best prediction for the boiling point of NaCl
A- NaCl will have a lower boiling point than NaG because the Coulombic attractions are weaker in NaCl than in NaG
47. Silicon crystals are semiconductors. Which of the following is a correct reason for the increase in the conductivity of Si crystals when a small fraction of Si atoms are replaced with those of a different element?
A- P atoms introduce additional mobile negative chargers
43.If the decomposition reaction were to go to completion, the total pressure in the container would be
B- 2.0 atm
55. Which of the four acids listed in the table is hydrochloride acid?
B- Acid 2
50. The figure above shows that in solid hydrogen fluoride there are two different distances between H atoms and F atoms. Which of the following best accounts for the two different distances?
B- Difference in strength between covalent bonds and intermolecular attractions.
44.Which of the following statements about K, the equilibrium constant for the reaction, is correct?
B- K<1
40. A student mixes dilute AgNO3 with excess NaCl to form AgCl, as represented by the net ionic equation above. Which of the diagrams below best represents the ions that are present in significant concentrations in the solution?
C- 2 ions of NO3, 2 ions of Cl, 4 ions of Na
61. Based on periodic grands and the data in the table above, which of the following are the most probable values of the atomic radius and the first ionization energy for potassium respectively?
C- 242 pm, 419 kJ/mol
62. Using the graduated cylinder illustrated on the right, what is the most correct volume?
C- 36.5mL
63. A measured mass of an unreactive metal was dropped into a small graduated cylinder half filled with water. The following measures were made. Using correct sig figs the density of the metal should be reported as:
C- 7.8 grams/mL
56. Of the following species, which had the greatest concentration in a 1.0M solution of acid 1 at equilibrium?
C- Acid 1
41. Which of the following is the most likely cause for the increase I pressure observed in the container as the reaction reaches equilibrium?
C- An increase in the number of molecules, which increases the frequency of collisions with the walls of the container
45. An organic compound which has the empirical formula CHO has a molar mass of 58. Its molecular formula is
C- C2H2O2
49. To make Au stronger and harder, it is often alloyed with other metals, such as Cu and Ag. Consider two alloys, one of Au and Cu and one of Au and Ag, each with the same mole fraction of Au. If the Au/Cu alloy is harder than the Au/Ag alloy, then which of the following is the best explanation based on the information in the table above?
C- Cu atoms are smaller than Ag atoms, thus they interfere more with the displacement of atoms in the alloy
59. The table above shows the values of K for four weak acids. Which of the following pairs of chemical species, when combined in equilmolar amounts, results in a buffer with a pH closest to 7.5?
C- HClO and ClO
52. Nonane and 2,3,4-trifluoropentane have almost identical molar masses, but nonane has significantly higher boiling point. Which of the following statements best helps explains this observation?
C- The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane
58. A 25 mL sample of a .1M solution of acid 1 is mixed with 25mL of .5M NaOH. Which of the following best explains best explains what happens to the pH of the mixture when a few drops of 1.0M HNO3 are added?
C- The pH of the mixture stays the same, because the conjugate base of acid 1 reacts with the added H3O ions
48. N2 molecules absorb ultraviolet light but not visible light. I2 molecules absorb both visible and ultraviolet light. Which of the following statements explains the observations?
C- Visible light does not produce transitions between electronic energy levels in the N2 molecule but does produce transition in the I2 molecule
42. As the reaction progresses toward equilibrium, the rate of the forward reaction
C- decreases to become a constant nonzero rate at equilibrium
64. Which of the following statements about atoms is NOT correct?
D- All atoms of a given element must have the same number of protons, neutrons, and electrons
57. Of equal volumes of the four acids at a concentration of .5M are each titrations with a strong base, which will require the greatest volume of base to reach the equivalence point?
D- All the acids will require the same volume of base to reach the equivalence point
60. Beaker X and Y each contain 1.0L of solution, as shown above. A student combines the solution by pouring them into a larger, previously empty beaker Z and observes the formation of a white precipitate. Assuming that the volumes are additive, which of the following sets of solutions could be represented by the diagram above?
D- Beaker X: 2.0M AgNO3 Beaker Y:1.0M MgCl Beaker Z: .5M Mg(NO3)2 and AgCl
51. The photoelectron spectra above show the energy required to remove a 1s electron from a nitrogen atom and from an oxygen. Which of the following statements best accounts for the peak in the upper spectrum being to the right of the peak in the lower spectrum?
D- Nitrogen atoms have a smaller nuclear charge than oxygen atoms
65. The mass spectrum of element X as represented above. Which of the following can be concluded about element X?
D- The atomic mass of X is between 90-92
66. Examining data obtained from mass spectrometry supports which of the following?
D- The existence is isotopes