ap chemistry MCQ

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• What is the energy change when 72.0 g of water vapor decomposes to the elements at constant pressure? The molar mass of H2O is 18.0 g mol-1.
  ক

  -1144 kJ

  খ

  -572 kJ

  গ

  +960 kJ

  ঘ

  +1144 kJ
• A solution of a weak base is titrated with a solution of a standard strong acid. The progress of the titration is followed with a pH meter. Which of the following observations would occur?
  ক

  Initially, the pH slowly decreases, then there is a rapid decrease to give a pH below 7 at the equivalence point.

  খ

  The pH of the solution gradually decreases throughout the experiment and the pH at the equivalence point is below 7.

  গ

  Initially, the pH slowly decreases, then there is a rapid decrease to give a pH equal to 7 at the equivalence point.

  ঘ

  Initially, the pH quickly decrease, then there is a gradual decrease to the equivalence point where the pOH equals the pKb of the base.
• According to the data in the table above, which of the following best explains the trend in increasing melting points?
  ক

  All the molecules are nonpolar and, for such molecules, intermolecular forces increase with increasing molar mass.

  খ

  All the molecules are polar and, for such molecules, intermolecular forces increase with increasing molar mass.

  গ

  The molecules with the lower melting points are nonpolar and the molecules with the higher molar masses are polar.

  ঘ

  The sequence is a coincidence since all the molecules have the same intermolecular forces.
• Why do the melting points of the alkaline metal oxides decrease in the order CaO > SrO > BaO?
  ক

  Larger ions have higher lattice energies, which leads to lower melting points.

  খ

  Smaller ions have lower lattice energies, which leads to higher melting points.

  গ

  Larger ions have lower lattice energies, which leads to lower melting points.

  ঘ

  Smaller ions have a greater affinity for oxygen, which leads to a higher melting point.
• Which of the following is the correct order of increasing acid strength?
  ক

  H2SeO3 < H2SO3 < HClO < HBrO

  খ

  HClO < H2SeO3 < HBrO < H2SO3

  গ

  HBrO < HClO < H2SeO3 < H2SO3

  ঘ

  H2SO3 < H2SeO3 < HClO < HBrO
• A certain reaction is nonspontaneous under standard conditions, but becomes spontaneous at higher temperatures. What conclusions may be drawn under standard conditions?
  ক

  ?H < 0, ?S < 0 and ?G = 0

  খ

  ?H > 0, ?S < 0 and ?G > 0

  গ

  ?H < 0, ?S < 0 and ?G > 0

  ঘ

  ?H > 0, ?S > 0 and ?G > 0
• Choose the reaction expected to have the greatest decrease in entropy.
  ক

  C(s) + CO2(g) ? 2 CO(g)

  খ

  2 Na(s) + O2(g) ? Na2O2(s)

  গ

  CH4(g) + 2 O2(g) ? CO2(g) + 2 H2O(g)

  ঘ

  2 NI3(s) ? 3 I2(s) + N2(g)
• Which of the compounds in the above diagram is capable of participating in hydrogen bonding?
  ক

  C3H9N

  খ

  CH3F

  গ

  C2H6O

  ঘ

  C4H11N
• Oxidation of which of the following substances will yield a stronger acid?
  ক

  HNO2

  খ

  HNO3

  গ

  H2SO4

  ঘ

  H3PO4
• Which of the following explains why the pH of a hydroxylamine solution is lower than any of the other solutions?
  ক

  The -OH is capable of donating a hydrogen ion, which will lower the pH.

  খ

  The presence of carbon makes the bases less stable.

  গ

  The presence of the very electronegative oxygen inhibits the nitrogen atom from donating its electron pair.

  ঘ

  There is insufficient information to explain this observation.
• All the bases in the diagram behave as Brønsted-Lowry bases in the same way; in each case, they accept a hydrogen ion to the same atom. How is this acceptance of a hydrogen ion accomplished?
  ক

  A hydrogen ion attaches to the lone pair on the nitrogen atom.

  খ

  The hydroxide ion reacts with the hydrogen ion to form water.

  গ

  The hydrogen ion forms a hydrogen bond to the base.

  ঘ

  The hydrogen ion combines with a hydrogen atom from the base to form H2 gas.
• If the moles of HCl in container B are equal to five times the O2 present, what can be said about the moles of O2 present at equilibrium?
  ক

  It will be zero because it is the limiting reagent

  খ

  It will remain the same

  গ

  It will be increase

  ঘ

  It is impossible to determine
• If the initial partial pressure of Cl2 in container A is 1.0 atm and the initial partial pressure of H2O is also 1.0 atm, what will be the pressure at equilibrium?
  ক

  > 2.0 atm

  খ

  = 2.0 atm

  গ

  < 2.0 atm

  ঘ

  Impossible to determine
• An equilibrium mixture (container D) is at 75°C. Which of the following changes may increase the amount of the HCl in the container?
  ক

  Increasing the volume of the container

  খ

  Decreasing the volume of the container

  গ

  Lowering the temperature of the container

  ঘ

  Adding 1 mole of He(g) to the container
• Which of the gases will show the greatest deviation from ideal behavior?
  ক

  He

  খ

  Ne

  গ

  Ar

  ঘ

  Kr
• Assuming all four gases are behaving ideally, which of the following is the same for all the gas samples?
  ক

  Average kinetic energy of the atoms

  খ

  Average speed of the atoms

  গ

  Density of the gas in the container

  ঘ

  All properties are the same for gases behaving ideally
• If a sample of Kr effuses at a rate of 35 mL per second at 298 K, which of the gases below will effuse at approximately double the rate under the same conditions?
  ক

  Ar

  খ

  He

  গ

  Ne

  ঘ

  Impossible to determine
• What is the rate law for the reaction?
  ক

  Rate = k[N2O5]2

  খ

  k = [N2O5]

  গ

  Rate = k[N2O5]

  ঘ

  D.
• The above represents a proposed mechanism for the gaseous dinitrogen pentoxide, N2O5. What are the overall products of the reaction?
  ক

  N2O4(g) + O2(g)

  খ

  2 NO2(g) + O2(g)

  গ

  N2O4(g) + NO2(g) + O2(g)

  ঘ

  4 NO2(g) + O2(g)
• At what point on the graph for the titration of pure sodium carbonate is the pH = pKa2 for carbonic acid?
  ক

  At point G

  খ

  Halfway between the start and point G

  গ

  At point H

  ঘ

  Halfway between points G and H
• In addition to water, what are the predominant species in solution at F?
  ক

  Na2CO3 and HCl

  খ

  Na+, Cl-, and H2CO3

  গ

  HCO3- and H+

  ঘ

  Na+, Cl-, H+, and CO32-
• How could a student determine if there was a strong acid or a strong base contaminant in the original sample?
  ক

  The presence of an acid contaminant would require less acid to reach H from G than to reach G from 0.

  খ

  The presence of a base contaminant would require less acid to reach G from 0 than to reach F from G.

  গ

  The presence of a base contaminant would require more acid to reach G from 0 than to reach F from G.

  ঘ

  It is impossible to determine.
• A trial run used a sample of pure sodium carbonate. How does the volume of acid necessary to reach G from 0 compare to the volume of acid necessary to get from G to H?
  ক

  They are the same.

  খ

  It takes more to reach point G.

  গ

  It takes more to get from G to H.

  ঘ

  It is impossible to determine.
• Given the above standard reduction potentials, estimate the approximate value of the ?G° for the following reaction:
  ক

  -4.6 × 104 J mol-1

  খ

  -9.3 × 104 J mol-1

  গ

  +9.3 × 104 J mol-1

  ঘ

  +4.6 × 104 J mol-1
• How many grams of water were in the hydrate?
  ক

  5.557 g

  খ

  4.737 g

  গ

  0.987 g

  ঘ

  0.820 g
• What happens to the cell voltage after the cell has reached equilibrium?
  ক

  There is no change in the voltage.

  খ

  The voltage becomes zero.

  গ

  The voltage increases.

  ঘ

  The voltage decreases, but stays positive.
• If the standard reduction potential of silver is 0.80 V, what is the standard reduction potential of zinc?
  ক

  +0.76 V

  খ

  -0.76 V

  গ

  -0.04 V

  ঘ

  +0.04 V
• What happens to the cell voltage when the student replaces the Zn(NO3)2 solution with 1 M ZnCl2?
  ক

  There is no change in the voltage.

  খ

  The voltage becomes zero.

  গ

  The voltage increases.

  ঘ

  The voltage decreases, but stays positive.
• What happens to the voltage when a small amount of silver nitrate is added to the silver compartment?
  ক

  There is no change in the voltage.

  খ

  The voltage becomes zero.

  গ

  The voltage increases.

  ঘ

  The voltage decreases, but stays positive.
• Which of the labeled arrows in the diagram above represents the strongest intermolecular force?
  ক

  A

  খ

  B

  গ

  C

  ঘ

  D