Chemistry AP 2016

12. Compound KSP PbCl₂ - 1.2 x 10⁻⁵ CuCl - 1.6 x 10⁻⁷ AgCl 1.8 x 10⁻18 Based on the Ksp values in the table above, a saturated solution of which of the following compounds has the highest Cl⁻? A. PbCl2 B. CuCl C. AgCl D. Hg2Cl2

A

20. iHX + Y⁻ ⇌ HY + X⁻ Keq > 1 Based on the information given above, which of the following is the strongest acid? A. HX B. Y⁻ C HY D. X ⁻

A

25. A student mixes 10.0 ml sample of 1.0 M NaOH with 10.0 ml sample of 1.0 M HCl in a polystyrene container. The temperature of the solutions before mixing was 20.0 °C. IF the final temperature of the solutions before mixing was 20.0°C. If the final temperature of the mixture is 26.0°C , what is the experimental value of ∆H ? (Assume that the solution mixture has a specific heat of 4.2 J/ (G*K) and a density of 1.0 g/ mL. A. -50 kJ.mol B. -25 C. -5.0 x 10⁴ D. -5.0 x 10²

A

3. A sample of a hard, solid binary compound at room temperature did not conduct electricity as a pure solid but became highly conductive when dissolved in water. Which of the following types of interactions is most likely found between the particles in the substance? A. Ionic bonds B. Metallic bonds C. Covalent bonds D. Hydrogen bonds?

A

42. 2 H₂S(g) + CH₄(g) ⇌ CS₂(g) + 4 H₂ Kc = 3.4 x 10⁻⁴ A 0.10 mol sample of each of the four species in the reaction represented above is injected into a rigid, previously evacuated 1.0 L container. Which of the following species will have the highest concentration when the system reaches equilibrium? A. H₂S B. CH₄ C. CS₂ D. H₂

A

47. CH₃OH → CO(g) + 2H₂ ∆H = 91 kJ The reaction is represented above goes essentially to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600K. Which of the following statements about the bonds in the reactants and products is most accurate? A. The sum of the bond enthalpies of the bonds in the reactant is greater than the sum of the bond enthalpies of the bonds in the products. B. The sum of the bond enthalpies of the bonds in the reactants is less than the sum of the bond enthalpies of the bonds in the products? C. The lengths of the bond between carbon and oxygen in CH₃OH is shorter than the length of the bond between carbon and oxygen in CO. D. All of the bonds in the reactant and products are polar.

A

5. Which of the following arranges the molecules N₂, O₂, and F₂ in order of their bond enthalpies from least to greatest? A. F₂ < O₂ < N₂ B. O₂ < N₂ < F₂ C. N₂ < O₂ < F₂ D. N₂ < F₂ < O₂

A

7. Element - Electronegativity H 2.1 C 2.5 S. 2.5 F 4.0 Cl 3.0 Si 1.8 On the basis of the information above, which of the following arranges the binary compounds in order of increasing polarity? A. CH₄ < SiCL₄ < SF₄ B. CH₄ < SF₄ < SiCl₄ C. SF₄ < CH₄ < SiCl₄ D. SiCl₄ < SF₄ < CH₄

A

11.A 23.0 g sample of a compound contains 12.0 g of C, 3.0 g of H, and 8.0 g of O. Which of the following is the empirical formula of the compound? A. CH₃O B. C₂H₆O₂ C. C₃H₉O₂ D. C₄H₁₂O₂

B

16. C₂H₄ + H₂ --> C₂H₆ Which of the following will most likely increase the rate of the reaction represented above? A. Decreasing the temperature of the reaction system B. Adding a heterogeneous catalyst to the reaction system C. Increasing the volume of the reaction vessel using a piston. D. Removing some H₂ from the reaction system?

B

19. Element - molar mass - boiling point. CS₂- 76 - 46.5 CCl₄- 154- 76.7 Based on the information in the table above, which liquid CS₂ or CCl₄ has the higher equilibrium vapor pressure at 25°C and why? A. CS2 because it has stronger London Dispersion forces. B. CS2 because it has weaker London dispersion forces. C. CCl4 because it has weaker London dispersion forces. D. CCl4 because it has weaker London dispersion forces.

B

24. Trial - Volume of 0.10 M HCL - Volume of 0,10 NaOH - heat released 1- 50 ml - 50 ml - x 2- 100 ml - 50 ml - y A student conducted an experiment to determine ∆H for the reaction between HCl and NaOh. The student ran two trials using the volumes of HCl and NaOH indicate in the table above, and determined the amount of heat released. Which of the following best explains the relationship between X and Y. A. Y = 2X because the volume of HCl used in trial 2 is twice the volume used in trial 1. B. Y = X because the number of moles of acid and base reacting with each other is the same in both trials. C. Y = 2x/3 because the heat is distributed over more particles in trial 2 than in trial 1. D. The relationship between X and Y cannot be predicted.

B

26. 2 NO₂ + F₂ --> 2NO₂F The rate law for the reaction represented by the equation above is rate k [NO₂] [ F₂]. Which of the following could be the first elementary step of a two - step mechanism for the reaction if the first step is slow and the second step is fast? A. F₂ →2 F B. NO₂ + F₂ → No₂F + F C. NO₂ + F → NO₂F D. 2 NO₂ + F₂ →2NO₂F

B

28. A mixture containing equal numbers of moles of ethyl acetate and butyl acetate was separated using distillation. Based on the diagrams shown above, which of the following identities the substance that would be initially present in higher concentration int he distillate and correctly explains why that occurs? A. Ethyl acetate because it has fewer C-C bonds to break B. Ethyl acetate because it has a shorter carbon chain and weaker London dispersion forces. C. Butyl acetate because it has more C-C bonds to break. D. Butyl acetate, because it has a longer carbon chain and weaker dipole - dipole attractions.

B

30. What would be the effect on the reaction rate if the solution of C₂₅H₃₀N₃ ⁺ is diluted by a factor of two? A. It would be higher B. It would be lower C. It would not change D. IT would initially be higher but then rapidly decrease.

B

34. The pH of a 0.01 M HNO₂ solution is in which of the following ranges? (For HNO₂(aq) = Ka = 4.0 x 10⁻⁴) A. Between 1 and 2 B. Between 2 and 3 C. Between 4 and 5 D. Between 6 and 7

B

43. See graph. At 1.0 atm a sample of ice is heated to liquid water and then to water vapor. The heating curve is shown in the graph above . Which of the following lists the signs for the changes in enthalpy and entropy for the process corresponding to segment X , going from left to right? ∆H-∆S A. Positive, Negative B. Positive , Positive C. Negative , Negative D. Negative, Positive

B

6. Ion- Ion Radius (pm) Li⁺ - 60 Na⁺ - 95 Ca²⁺ - 99 In³⁺ - 81 Based on Coulomb's law and the information in the table above, which of the following cations is most likely to have the weakest interaction with an adjacent water molecule in an aqueous solution? A. Li⁺ B. Na⁺ C. Ca²⁺ D. In³⁺

B

14. 2 H₂O₂ → 2 H₂O + O₂ E° = 0.55 V The equation and standard cell potential for the decomposition of H2O2 in acidic solution of 25°C is given above. O₂ + 4 H⁺ + 4 e --> 2 H₂O E°= 1.23 V O₂ + 2 H⁺ + 2 e⁻ --> H₂O₂ E° = ? What is the standard reduction potential for the half-reaction represented above? A. -1.78 B. - 0.68 C. + 0.68 D. + 1.78

C

15. 2 H₂O₂ → 2 H₂O + O₂ E° = 0.55 V The equation and standard cell potential for the decomposition of H2O2 in acidic solution of 25°C is given above. O₂ + 4 H⁺ + 4 e --> 2 H₂O E°= 1.23 V O₂ + 2 H⁺ + 2 e⁻ --> H₂O₂ E° = ? Which of the following is true for the decomposition of H₂O₂(aq)? A. ∆G° > 0 and Keq > 1 B. ∆G° > 0 and Keq < 1 C. ∆G° < 0 and Keq > 1 D. ∆G° < 0 and Keq < 1

C

18. At room temperature I₂ is a molecular solid. Which of the following provides a characteristic of I₂ with a correct explanation. A. It has a high melting point because it has weak intermolecular forces. B. It is hard because it forms a three- dimensional covalent network. C. It is not a good conductor of electricity because its valence electrons are localized in bonding and nonbonding pairs. D. It is very soluble in water because its molecules are polar.

C

29. Approximately how long did it take for 75 percent of the initial amount of C₂₅H₃₀N₃ ⁺ to react? A. 75s B. 225 s C. 300 s D. 600 s

C

31. The student wants to use the spectrophotometer to measure C₂₅H₃₀N₃ ⁺ with the greatest sensitivity as the reaction progress. Which of the following indicates the best wavelength setting and explain why it is the best? A. 205 nm because the colorless form of the molecule will absorb significantly at this wavelength. B. 205 nm because both forms of the molecule will absorb significantly at this wavelength. C. 590 nm because only the violet form of the molecule will absorb significantly at this wavelength. D. 590 nm because this wavelength falls in the violege region of the visible light spectrum.

C

32. CO + H₂O ⇌ CO₂ + H₂ Kc = 1.5x10³ A 2.0 mol sample of CO(g) and a 2.0 mol sample of H₂O are introduced into a previously evacuated 100 L rigid container, and the temperature is held constant as the reaction represented above reaches equilibrium. Which of the following is true at equilibrium? a. [H₂O] > [CO] and [CO₂] > [H₂] b. [H₂O] > [H₂] c. [CO₂] > [CO] d. [CO] = [H₂O] = [CO₂] = [H₂]

C

33. Compound KSP Ag₂SO₄ 1x10⁻⁵ PbSO₄ 1x10⁻⁸ A 1.0 L solution of AgNO₃ and Pb(NO₃)₂ has a Ag⁺ concentration of 0.020 M and a Pb²⁺ concentration of 0.0010 M. A 0.0010 mol sample of K₂SO₄ is added to the solution. Based on the information in the table above, which of the following will occur? (Assume that the volume change of the solution is negligible) A. no precipitate will form B. Only Ag2SO4 will precipitate. C. Only PbSO4 will precipitate. D. Both Ag2SO4 and PbSO4 will precipitate.

C

37. When water is added to a mixture of Na₂O₂ and S, a redox reaction occurs, as represented by the equation below. 2Na₂O₂(s) + S(s) + 2 H₂O → 4 NaOH(aq) + SO₂(aq) ∆H= -610 kJ/mol ; ∆S = -7.3 J/ (K*mol) Two trials are run, using excess water. In the first trial, 7.8 g of Na₂O₂ (mm=78g) is mixed with 3.2 g of S(s). In the second trial, 7.8 g of Na₂O₂ and S react as completely as possible. Both trials yield the same amount of SO₂. Which of the following identifies the limiting reagent and the heat released, q, for the two trials of 298 K? Limiting reactant - q A. S , 30KJ B. S, 61 KJ C. Na₂O₂ , 30 kJ D. Na₂O₂ , 61 kJ

C

38. When water is added to a mixture of Na₂O₂ and S, a redox reaction occurs, as represented by the equation below. 2Na₂O₂(s) + S(s) + 2 H₂O → 4 NaOH(aq) + SO₂(aq) ∆H= -610 kJ/mol ; ∆S = -7.3 J/ (K*mol) Atoms of which element are reduced in the reaction? A. S; each atom loses four electrons B. Na is Na₂O₂ ; each atoms loses one electron. C. O in Na₂O₂; each atoms gains one electron D. O in H₂O; each atom gains one electron.

C

39. Which of the following statements about the thermodynamic favorability of the reaction at 298 K is correct? A. It is thermodynamically unfavorable. B. It is thermodynamically favorable and is driven by ∆S only. C. It is thermodynamically favorable and is driven by ∆H only. D. It is thermodynamically favorable and is driven by both ∆H and ∆S

C

41. Ionization energy 1st- 577 2nd- 1,816 3rd- 2,745 4th- 11,577 5th-14,482 Based on the ionization energies of element X given in table above, which of the following is most likely the empirical formula of an oxide of element X? A. XO₂ B X₂O C. X₂O₃ D. X₂O₅

C

44. CH₃OH → CO(g) + 2H₂ ∆H = 91 kJ The reaction is represented above goes essentially to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600K. What happens to the temperature of the contents of the vessel as the reaction occurs? A. The temperature must increase, because according to Le Chatelier's principle , an increase in temperature causes more products to form. B. The temperature must decrease, because the reaction takes place at a temperature above room temperature. C. The temperature must decrease. because the reaction is endothermic. D. The temperature does not change, because the vessel is insulated.

C

46. CH₃OH → CO(g) + 2H₂ ∆H = 91 kJ The reaction is represented above goes essentially to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600K. What can be inferred about ∆S for the reaction at 600 K? A. It must be positive, since the reaction is thermodynamically unfavorable at 600 K B. It must be negative, since there are more moles of products than reactants. C. It must be positive, since ∆G is negative and ∆S is positive D. It must be negative, since ∆G is positive and ∆H is positive.

C

8. X → X⁺ + e⁻ IE₁ = 740 kJ/mol X⁺ → X²⁺ + e⁻ IE₂ = 2450 X²⁺ → X³⁺ + 3⁻ IE3= 7730 For element X represented above, which of the following is the most likely explanation for the large difference between the second and third ionization energies? A. The effective nuclear charge decreases with successive ionizations. B. The shielding of outer electrons increases with successive ionizations. C. The electron removed during the third ionization is, on average, much closer to the nucleus than the first two electrons removed were. D. The ionic radius increases with successive ionizations.

C

1. In which of the following liquids do the intermolecular forces include dipole dipole? A. F₂ B. CH₄ C. CF₄ D. CH₂F₂

D

2. Which of the following best helps explain why an increase in temperature increases the rate of a chemical reaction? A. At higher temperatures, reactions have a lower activation energy. B. At a higher temperatures, reactions have a higher activation energy. C. At a higher temperatures, every collision results in the formation of product. D. At higher temperatures, high-energy collisions happen more frequently.

D

21. AgNo₃ + NaCl → AgCl + NaNo₃ A student performed an analysis to determine the amount of AgNo₃ in a solution. Excess Nacl was added to the solution and the AG⁺ precipitated as AGCl. The precipitate was collected by gravity filtration and tried in an oven. Three trials were performed and in each case, according to the instructor, the mass of precipitate recovered was 5 percent higher than the actual mass of AgCl that should have formed. Which of the following could account for the error? A. The pores in the filter paper were too large. B. Not all of the precipitate was transferred to the filter paper. C. The NaCl solution was too concentrated. D. The precipitate was not rinsed with deionized water before drying.

D

35. graph. The photoelectron spectra of the 1s electrons of two isoelectronic species, Ca²⁺ and Ar are shown above. Which of the following correctly identifies the species associated with peak X and provides a valid justification? A. Ar, because it has completely filled energy levels. B. Ar because its radius is smaller than the radius of Ca2+ C. Ca2+ because its nuclear mass is greater than that of Ar. D. Ca2+ because its nucleus has two more protons than the nucleus of Ar has.

D

36. A vessel contains Ar(g) at a high pressure. Which of the following statements best helps to explain why the measured pressure is significantly greater than the pressure calculated using the ideal gas law? A. The molar mass of Ar is relatively large. B. A significant number of Ar₂ molecules form. C. The attractive forces among Ar atoms cause them to collide with the walls of the container with less force. D. The combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container.

D

4. N₂ + 3 H₂ ↔2 NH₃ ∆H <0 NH₃ was synthesized at 200°C in the presence of a powdered Os catalyst, leading to the equilibrium system represented above. Which of the following changes would result in more NH₃ in the mixture after equilibrium is reestablished? A. Replacing the powdered Os(s) with a solid cube of Os(s) of the same total mass. B. Increasing the temperature of the system to 250°C at constant pressure. C. Removing some H₂(g) D. Adding some N₂(g)

D

45. CH₃OH → CO(g) + 2H₂ ∆H = 91 kJ The reaction is represented above goes essentially to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600K. It must be positive, since the reaction is thermodynamically unfavorable at 600k. What is the final pressure in the vessel after the reaction is complete and the contents of the vessel are returned to 600 K? A. P₁/0 B. P₁/3 C. P₁ D. 3P₁

D

48. Acid - concentration - pH X - 0.005M - 2.3 Y- 2.0 M - 2.8 Z- 3.0 M - 2.8 Which of the following correctly ranks the three monoprotic acids listed in the table above from the weakest to strongest? A. X< Y<Z B. X<Z<Y C. Y<Z<X D. Z<Y<X

D

49. Element- Known oxides H- H2O , H2O2 Li - Li2O, Li2O2 Na- Na2O, Na2O2, NaO2 K- K2O, K2O2, KO2 Based on the information above and periodic trends, which of the following is the best hypothesis regarding the oxide formed by Rb? A. Rb will form only Rb2O B. Rb will form only RbO2 C. Rb will form only Rb2O and Rb2O2 D. Rb will form Rb2O, Rb2O2 and RbO2

D

50. Fe(s) + 2 HCl(aq) → FeCl₂(aq) + H₂(g) When a student adds 30.0 mL of 1.00 M HCl to 0.56 g of powdered Fe, a reaction occurs according to the equation above. When the reaction is complete at 273 L and 1.0 atm, which of the following is true? A. HCl is in excess, and 0.100 mol of HCl remains unreacted. B. HCl is in excess and 0.020 mol of Hcl remains unreacted. C. 0.015 mol of FeCl2 has been produced. D. 0.22 L of H2 has been produced.

D