AP Chem 1999 Multiple Choice

When hafnium metal is heated in an atmosphere of chlorine gas, the product of the reaction is found to contain 62.2 percent Hf by mass and 37.4 percent Cl by mass. What is the empirical formula for this compound? A) HfCl B) HfCl2 C) HfCl3 D) HfCl4 E) Hf2Cl3

C) HfCl3

. . . Li3N(s) + . . . H2O(l) → . . . Li+ (aq) + . . . OH-(aq) + . . . NH3(g) When the equation above is balanced and all coefficients reduced to lowest whole number terms, the coefficient for OH-(aq) is A) 1 B) 2 C) 3 D) 4 E) 6

C) 3

First / Second / Third / Fourth / Five 580 / 1,815 / 2,740 / 11,600 / 14,800 The ionization energies for element X are listed in the table above. On the basis of the data, element X is most likely to be A) Na B) Mg C) Al D) Si E) P

C) Al

*******PICTURE IN PACKET****** The phase diagram for a pure substance is shown above. Which point on the diagram corresponds to the equilibrium between the solid and liquid phases at the normal melting point? A) A B) B C) C D) D E) E

C) C

A) 1s 2s ↑ B) 1s ↓↑ 2s ↓↑ C) 1s ↓↑ 2s ↓↑ 2p ↑ ↑ D) 1s ↓↑ 2s ↓↑ 2p ↓↑ ↓↑ ↓↑ E) [Ar] 4s ↓↑ 3d ↓↑ ↑ ↑ ↑ ↑ Represents an atom of a transition metal

[Ar] 4s ↓↑ 3d ↓↑ ↑ ↑ ↑ ↑

A) 1s 2s ↑ B) 1s ↓↑ 2s ↓↑ C) 1s ↓↑ 2s ↓↑ 2p ↑ ↑ D) 1s ↓↑ 2s ↓↑ 2p ↓↑ ↓↑ ↓↑ E) [Ar] 4s ↓↑ 3d ↓↑ ↑ ↑ ↑ ↑ Represents an atom in an excited state

1s 2s ↑

A) 1s 2s ↑ B) 1s ↓↑ 2s ↓↑ C) 1s ↓↑ 2s ↓↑ 2p ↑ ↑ D) 1s ↓↑ 2s ↓↑ 2p ↓↑ ↓↑ ↓↑ E) [Ar] 4s ↓↑ 3d ↓↑ ↑ ↑ ↑ ↑ Represents an atom that has four valence electrons

1s ↓↑ 2s ↓↑ 2p ↑ ↑

A) 1s 2s ↑ B) 1s ↓↑ 2s ↓↑ C) 1s ↓↑ 2s ↓↑ 2p ↑ ↑ D) 1s ↓↑ 2s ↓↑ 2p ↓↑ ↓↑ ↓↑ E) [Ar] 4s ↓↑ 3d ↓↑ ↑ ↑ ↑ ↑ Represents an atom that is chemically unreactive

1s ↓↑ 2s ↓↑ 2p ↓↑ ↓↑ ↓↑

M(s) + 3 Ag+(aq) → 3 Ag(s) + M3+(aq) E° = +2.46 V Ag+(aq) + e- → Ag(s) E° = +0.80 V According to the information above, what is the standard reduction potential for the half-reaction M3+(aq) + 3 e- → M(s)? A) -1.66 V B) -0.06 V C) 0.06 V D) 1.66 V E) 3.26 V

A) -1.66 V

W(g) + X(g) → Y(g) + Z(g) Gases W and X react in a closed, rigid vessel to form gases Y and Z according to the equation above. The initial pressure of W(g) is 1.20 atm and that of X(g) is 1.60 atm. No Y(g) or Z(g) is initially present. The experiment is carried out at constant temperature. What is the partial pressure of Z(g) when the partial pressure of W(g) has decreased to 1.0 atm? A) 0.20 atm B) 0.40 atm C) 1.0 atm D) 1.2 atm E) 1.4 atm

A) 0.20 atm

NH4NO3(s) → N2O(g) + 2 H2O(g) A 0.03 mol sample of NH4NO3(s) is placed in a 1 L evacuated flask, which is then sealed and heated. The NH4NO3(s) decomposes completely according to the balanced equation above. The total pressure in the flask measured at 400 K is closest to which of the following? ( The value of the gas constant, R, is 0.082 L atm mol-1 K-1) A) 3 atm B) 1 atm C) 0.5 atm D) 0.1 atm E) 0.03 atm

A) 3 atm

AlF6 ^3- + 3 e- → Al + 6 F- Which of the following occurs in the reaction? A) AlF 63- is reduced at the cathode. B) Al is oxidized at the anode. C) Aluminum is converted from the -3 oxidation state to the 0 oxidation state. D) F- acts as a reducing agent. E) F- is reduced at the cathode.

A) AlF 63- is reduced at the cathode.

HC2H3O2(aq) + CN-(aq) p HCN(aq) + C2H3O2-(aq) The reaction represented above has an equilibrium constant equal to 3.7 × 104. Which of the following can be concluded from this information? A) CN-(aq) is a stronger base than C2H3O2-(aq). B) HCN(aq) is a stronger acid than HC2H3O2(aq). C) The conjugate base of CN-(aq) is C2H3O2-(aq). D) The equilibrium constant will increase with an increase in temperature. E) The pH of a solution containing equimolar amounts of CN-(aq) and HC2H3O2(aq) is 7.0.

A) CN-(aq) is a stronger base than C2H3O2-(aq).

Appropriate uses of a visible-light spectrophotometer include which of the following? I. Determining the concentration of a solution of Cu(NO3)2 II. Measuring the conductivity of a solution of KMnO4 III. Determining which ions are present in a solution that may contain Na+, Mg2+, Al3+ A) I only B) II oAnly C) III only D) I and II only E) I and III only

A) I only

Which of the following compounds is NOT appreciably soluble in water but is soluble in dilute hydrochloric acid? A) Mg(OH)2(s) B) (NH4)2CO3(s) C) CuSO4(s) D) (NH4)2SO4(s) E) Sr(NO3)2(s)

A) Mg(OH)2(s)

Equal numbers of moles of He(g), Ar(g), and Ne(g) are placed in a glass vessel at room temperature. If the vessel has a pinhole-sized leak, which of the following will be true regarding the relative values of the partial pressures of the gases remaining in the vessel after some of the gas mixture has effused? A) PHe < PNe < PAr B) PHe < PAr < PNe C) PNe < PAr < PHe D) PAr < PHe < PNe E) PHe = PAr = PNe

A) PHe < PNe < PAr

A yellow precipitate forms when 0.5 M NaI(aq) is added to a 0.5 M solution of which of the following ions? A) Pb2+(aq) B) Zn2+(aq) C) CrO4^2-(aq) D) SO4^2-(aq) E) OH-(aq)

A) Pb2+(aq)

When solid ammonium chloride, NH4Cl(s) is added to water at 25 °C, it dissolves and the temperature of the solution decreases. Which of the following is true for the values of ΔH and ΔS for the dissolving process? ΔH ΔS A) Positive Positive B) Positive Negative C) Positive Equal to zero D) Negative Positive E) Negative Negative

A) Positive Positive

Which of the following gases deviates most from ideal behavior? A) SO2 B) Ne C) CH4 D) N2 E) H2

A) SO2

When 100 mL of 1.0 M Na3PO4 is mixed with 100 mL of 1.0 M AgNO3, a yellow precipitate forms and [Ag+] becomes negligibly small. Which of the following is a correct listing of the ions remaining in solution in order of increasing concentration? A) [PO4^3-] < [NO3^-] < [Na+] B) [PO4^3-] < [Na+] < [NO3^-] C) [NO3^-] < [PO4^3-] < [Na+] D) [Na+] < [NO3^-] < [PO4^3-] E) [Na+] < [PO4^3-] < [NO3^-]

A) [PO4^3-] < [NO3^-] < [Na+]

The energy required to form the transition state in a chemical reaction

Activation energy

What mass of Au is produced when 0.0500 mol of Au2S3 is reduced completely with excess H2? A) 9.85 g B) 19.7 g C) 24.5 g D) 39.4 g E) 48.9 g

B) 19.7 g

Under which of the following sets of conditions could the most O2(g) be dissolved in H2O(l)? Pressure(atm) of O2(g) / Temperature(C) A) 5.0 80 B) 5.0 20 C) 1.0 80 D) 1.0 20 E) 0.5 20

B) 5.0 20

If 87.5 percent of a sample of pure 131I decays in 24 days, what is the half-life of 131I? A) 6 days B) 8 days C) 12 days D) 14 days E) 21 days

B) 8 days

In a qualitative analysis for the presence of Pb2+, Fe2+, and Cu2+ ions in a aqueous solution, which of the following will allow the separation of Pb2+ from the other ions at room temperature? A) Adding dilute Na2S(aq) solution B) Adding dilute HCl(aq) solution C) Adding dilute NaOH(aq) solution D) Adding dilute NH3(aq) solution E) Adding dilute HNO3(aq) solution

B) Adding dilute HCl(aq) solution

The melting point of MgO is higher than that of NaF. Explanations for this observation include which of the following? I. Mg2+ is more positively charged than Na+ II. O2- is more negatively charged than F- III. The O2- ion is smaller than the F- ion A) II only B) I and II only C) I and III only D) II and III only E) I, II, and III

B) I and II only

2 NO(g) + O2(g) p 2 NO2(g) ΔH < 0 Which of the following changes alone would cause a decrease in the value of Keq for the reaction represented above? A) Decreasing the temperature B) Increasing the temperature C) Decreasing the volume of the reaction vessel D) Increasing the volume of the reaction vessel E) Adding a catalyst

B) Increasing the temperature

A 1.0 L sample of an aqueous solution contains 0.10 mol of NaCl and 0.10 mol of CaCl2. What is the minimum number of moles of AgNO3 that must be added to the solution in order to precipitate all of the Cl- as AgCl(s) ? (Assume that AgCl is insoluble.) A) 0.10 mol B) 0.20 mol C) 0.30 mol D) 0.40 mol E) 0.60 mol

C) 0.30 mol

*******PICTURE IN PACKET****** The graph above shows the results of a study of the reaction of X with a large excess of Y to yield Z. The concentrations of X and Y were measured over a period of time. According to the results, which of the following can be concluded about the rate law for the reaction under the conditions studied? A) It is zero order in [X]. B) It is first order in [X]. C) It is second order in [X]. D) It is the first order in [Y]. E) The overall order of the reaction is 2.

B) It is first order in [X].

After completing an experiment to determine gravimetrically the percentage of water in a hydrate, a student reported a value of 38 percent. The correct value for the percentage of water in the hydrate is 51 percent. Which of the following is the most likely explanation for this difference? A) Strong initial heating caused some of the hydrate sample to spatter out of the crucible. B) The dehydrated sample absorbed moisture after heating. C) The amount of the hydrate sample used was too small. D) The crucible was not heated to constant mass before use. E) Excess heating caused the dehydrated sample to decompose.

B) The dehydrated sample absorbed moisture after heating.

A molecule or an ion is classified as a Lewis acid if it A) accepts a proton from water B) accepts a pair of electrons to form a bond C) donates a pair of electrons to form a bond D) donates a proton to water E) has resonance Lewis electron-dot structures

B) accepts a pair of electrons to form a bond

Experiment Initial [NO] (mol L-1) 1- 0.10 2- 0.20 3- 0.20 Initial [O2] (mol L-1) 1- 0.10 2- 0.10 3- 0.40 Initial Rate of Formation of NO2 (mol L-1 s-1) 1- 2.5 × 10-4 2- 5.0 × 10-4 3- 8.0 × 10-3 The initial-rate data in the table above were obtained for the reaction represented below. 2 NO + O2 → 2 NO2 What is the experimental rate law for the reaction? A) rate = k[NO] [O2] B) rate = k[NO] [O2]2 C) rate = k[NO]2 [O2] D) rate = k[NO]2 [O2]2 E) rate = k[NO] / [O2

B) rate = k[NO] [O2]2

When a solution of sodium chloride is vaporized in a flame, the color of the flame is A) blue B) yellow C) green D) violet E) white

B) yellow

AlF6 ^3- + 3 e- → Al + 6 F- As steady current of 10 amperes in passed though an aluminum-production cell for 15 minutes. Which of the following is the correct expressions for calculating the number of grams of aluminum produced? (1 faraday = 96,500 coulombs) A) (10)(15)(96500)/(27)(60) g B) (10)(15)(27)/(60)(96500) g C) (10)(15)(60)(27)/(96500)(3) g D) (96500)(27)/(10)(15)(60)(3) g E) (27)(3)/(96500)(10)(15)(60) g

C) (10)(15)(60)(27)/(96500)(3) g

A 40.0 mL sample of 0.25 M KOH is added to 60.0 mL of 0.15 M Ba(OH)2. What is the molar concentration of OH-(aq) in the resulting solution? (Assume that the volumes are additive.) A) 0.10 M B) 0.19 M C) 0.28 M D) 0.40 M E) 0.55 M

C) 0.28 M

. . . C10H12O4S(s) + . . O2(g) → . . . CO2(g) + . . . SO2(g) + . . . H2O(g) When the equation above is balanced and all coefficients are reduced to their lowest whole-number terms, the coefficient for O2(g) is? A) 6 B) 7 C) 12 D) 14 E) 28

C) 12

A rigid metal tank contains oxygen gas. Which of the following applies to the gas in the tank when additional oxygen is added at constant temperature? A) The volume of the gas increase. B) The pressure of the gas decreases. C) The average speed of the gas molecules remains the same. D) The total number of gas molecules remains the same. E) The average distance between the gas molecules increases.

C) The average speed of the gas molecules remains the same.

Which of the following occurs when excess concentrated NH3(aq) is mixed thoroughly with 0.1 M Cu(NO3)2(aq)? A) A dark red precipitate forms and settles out. B) Separate layers of immiscible liquids form with a blue layer on top. C) The color of the solution turns from light blue to dark blue. D) Bubbles of ammonia gas form. E) The pH of the solution decreases.

C) The color of the solution turns from light blue to dark blue.

If the temperature of an aqueous solution of NaCl is increased from 20°C to 90°C, which of the following statements is true? A) The density of the solution remains unchanged. B) The molarity of the solution remains unchanged. C) The molality of the solution remains unchanged. D) The mole fraction of solute decreases. E) The mole fraction of solute increases.

C) The molality of the solution remains unchanged.

Which of the following best describes the role of the spark from the spark plug in an automobile engine? A) The spark decreases the energy of activation for the slow step. B) The spark increases the concentration of the volatile reactant. C) The spark supplies some of the energy of activation for the combustion reaction. D) The spark provides a more favorable activated complex for the combustion reaction. E) The spark provides the heat of vaporization for the volatile hydrocarbon.

C) The spark supplies some of the energy of activation for the combustion reaction.

*******PICTURE IN PACKET****** The cooling curve for a pure substance as it changes from a liquid to a solid is shown above. The solid and the liquid coexist at A) point Q only B) point R only C) all points on the curve between Q and S D) all points on the curve between R and T E) no point on the curve

C) all points on the curve between Q and S

On a mountaintop, it is observed that water boils at 90°C, not at 100°C as at sea level. This phenomenon occurs because on the mountaintop the A) equilibrium water vapor pressure is higher due to the higher atmospheric pressure B) equilibrium water vapor pressure is lower due to the higher atmospheric pressure C) equilibrium water vapor pressure equals the atmospheric pressure at a lower temperature D) water molecules have a higher average kinetic energy due to the lower atmospheric pressure E) water contains a greater concentration of dissolved gases

C) equilibrium water vapor pressure equals the atmospheric pressure at a lower temperature

Strong multiple covalent bonds (including π bonds) with weak intermolecular forces A)Cesium chloride, CsCl(s) B)Gold, Au(s) C)Carbon dioxide, CO2(s) D)Methane, CH4(s)

Carbon dioxide, CO2(s)

Lattice of positive and negative ions held together by electrostatic forces A)Cesium chloride, CsCl(s) B)Gold, Au(s) C)Carbon dioxide, CO2(s) D)Methane, CH4(s)

Cesium chloride, CsCl(s)

The energy required to convert a ground-state atom in the gas phase to a gaseous positive ion

Ionization energy

What is the final concentration of barium ions, [Ba2+], in solution when 100. mL of 0.10 M BaCl2(aq) is mixed with 100. mL of 0.050 M H2SO4(aq)? A) 0.00 M B) 0.012 M C) 0.025 M D) 0.075 M E) 0.10 M

D) 0.075 M

The volume of distilled water that should be added to 10.0 mL of 6.00 M HCl(aq) in order to prepare a 0.500 M HCl(aq) solution is approximately A) 50.0 mL B) 60.0 mL C) 100. mL D) 110. mL E) 120. mL

D) 110. mL

10 HI + 2 KMnO4 + 3 H2SO4 → 5 I2 + 2 MnSO4 + K2SO4 + 8 H2O According to the balanced equation above, how many moles of HI would be necessary to produce 2.5 mol of I 2, starting with 4.0 mol of KMnO4 and 3.0 mol of H2SO4? A) 20 B) 10 C) 8.0 D) 5.0 E) 2.5

D) 5.0

What is the H+(aq) concentration in 0.05 M HCN (aq)? (The Ka for HCN is 5.0 × 10-10) A) 2.5 × 10-11 B) 2.5 × 10-10 C) 5.0 × 10-10 D) 5.0 × 10-6 E) 5.0 × 10-4

D) 5.0 × 10-6

In which of the following processes are covalent bonds broken? A) I2(s) → I2(g) B) CO2(s) → CO2(g) C) NaCl(s) → NaCl(l) D) C(diamond) → C(g) E) Fe(s) → Fe(l)

D) C(diamond) → C(g)

The safest and most effective emergency procedure to treat an acid splash on skin is to do which of the following immediately? A) Dry the affected area with paper towels. B) Sprinkle the affected area with powdered Na2SO4(s). C) Flush the affected area with water and then with a dilute NaOH solution. D) Flush the affected area with water and then with a dilute NaHCO3 solution. E) Flush the affected area with water and then with a dilute vinegar solution.

D) Flush the affected area with water and then with a dilute NaHCO3 solution.

Of the following molecules, which has the largest dipole moment? A) CO B) CO2 C) O2 D) HF E) F2

D) HF

Types of hybridization exhibited by the C atoms in propene, CH3CHCH2, include which of the following? I. sp II. sp2 III. sp3 A) I only B) III only C) I and II only D) II and III only E) I, II, and III

D) II and III only

In the periodic table, as the atomic number increases from 11 to 17, what happens to the atomic radius? A) It remains constant. B) It increases only. C) It increases, then decreases. D) It decreases only. E) It decreases, then increases.

D) It decreases only.

A sample of 61.8 g of H3BO3, a weak acid is dissolved in 1,000 g of water to make a 1.0-molal solution. Which of the following would be the best procedure to determine to molarity of the solution? (Assume no additional information is available.) A) Titration of the solution with standard acid B) Measurement of the pH with a pH meter C) Determination of the boiling point of the solution D) Measurement of the total volume of the solution E) Measurement of the specific heat of the solution

D) Measurement of the total volume of the solution

H2Se(g) + 4 O2F2(g) → SeF6(g) + 2 HF(g) + 4 O2(g) Which of the following is true regarding the reaction represented above? A) The oxidation number of O does not change. B) The oxidation number of H changes from -1 to +1. C) The oxidation number of F changes from +1 to -1. D) The oxidation number of Se changes from -2 to +6. E) It is a disproportionation reaction for F.

D) The oxidation number of Se changes from -2 to +6.

C2H4(g) + 3 O2(g) → 2 CO2(g) + 2 H2O(g) For the reaction of ethylene represented above, ΔH is -1,323 kJ mol-1. What is the value of ΔH if the combustion produced liquid water H2O(l), rather than water vapor H2O(g)? (ΔH for the phase change H2O(g) → H2O(l) is -44 kJ mol-1.) A) -1,235 kJ/mol B) -1,279 kJ/mol C) -1,323 kJ/mol D) -1,367 kJ/mol E) -1,411 kJ/mol

E) -1,411 kJ/mol

Of the following reaction, which involves the largest decrease in entropy? A) CaCO3(s) → CaO(s) + CO2(g) B) 2 CO(g) + O2(g) → 2 CO2(g) C) Pb(NO3)3(s) + 2 KI(s) → PbI2(s) + 2 KNO3(s) D) C3H8(g) + O2(g) → 3 CO2(g) + 4 H2O(g) E) 4 La(s) + 3 O2(g) → 2 La2O3(s)

E) 4 La(s) + 3 O2(g) → 2 La2O3(s)

Which of the following techniques is most appropriate for the recovery of solid KNO3 from an aqueous solution of KNO3? A) Paper chromatography B) Filtration C) Titration D) Electrolysis E) Evaporation to dryness

E) Evaporation to dryness

A hot-air balloon, shown above, rises. Which of the following is the best explanation for this observation? A) The pressure on the walls of the balloon increases with increasing temperature. B) The difference in temperature between the air inside and outside the balloon produces convection currents. C) The cooler air outside the balloon pushes in on the walls of the balloon. D) The rate of diffusion of cooler air is less than that of warmer air. E) The air density inside the balloon is less than that of the surrounding air.

E) The air density inside the balloon is less than that of the surrounding air.

2 SO3 (g) p 2 SO2 (g) + O2 (g) After the equilibrium represented above is established, some pure O2 (g) is injected into the reaction vessel at constant temperature. After equilibrium is reestablished, which of the following has a lower value compared to its value at the original equilibrium? A) Keq for the reaction. B) The total pressure in the reaction vessel. C) The amount of SO3 (g) in the reaction vessel. D) The amount of O2 (g) in the reaction vessel. E) The amount of SO2 (g) in the reaction vessel.

E) The amount of SO2 (g) in the reaction vessel.

Which of the following is a correct interpretation of the results of Rutherford's experiments in which gold atoms were bombarded with alpha particles? A) Atoms have equal numbers of positive and negative charges. B) Electrons in atoms are arranged in shells. C) Neutrons are at the center of an atom. D) Neutrons and protons in atoms have nearly equal mass. E) The positive charge of an atom is concentrated in a small region.

E) The positive charge of an atom is concentrated in a small region.

*******PICTURE IN PACKET****** The organic compound represented above is an example of A) an organic acid B) an alcohol C) an ether D) an aldehyde E) a ketone

E) a ketone

67. What is the molar solubility in water of Ag2CrO4? (The Ksp for Ag2CrO4 is 8 × 10-12.) A) 8 × 10-12 M B) 2 × 10-12 M C) Sqrt (4 × 10−12 )M D) cube root (4 × 10−12 ) 3 M E) cube root (2 × 10−12 ) 3 M

E) cube root (2 × 10−12 ) 3 M

A) Lithium B) Nickel C) Bromine D) Uranium E) Fluorine Is a gas in its standard state at 298 K

Fluorine

The energy in a chemical or physical change that is available to do useful work

Free energy

Closely packed lattice with delocalized electrons throughout A)Cesium chloride, CsCl(s) B)Gold, Au(s) C)Carbon dioxide, CO2(s) D)Methane, CH4(s)

Gold, Au(s)

A) NH3 and NH4Cl B) H3PO4 and NaH2PO4 C) HCl and NaCl D) NaOH and NH3 E) NH3 and HC2H3O2 (acetic acid) A buffer at a pH < 6

H3PO4 and NaH2PO4

A) NH3 and NH4Cl B) H3PO4 and NaH2PO4 C) HCl and NaCl D) NaOH and NH3 E) NH3 and HC2H3O2 (acetic acid) The solution with the lowest pH

HCl and NaCl

The energy change that occurs in the conversion of an ionic solid to widely separated gaseous ions

Lattice energy

A) Lithium B) Nickel C) Bromine D) Uranium E) Fluorine Reacts with water to form a strong base

Lithium

Strong single covalent bonds with weak intermolecular forces A)Cesium chloride, CsCl(s) B)Gold, Au(s) C)Carbon dioxide, CO2(s) D)Methane, CH4(s)

Methane, CH4(s)

A) NH3 and NH4Cl B) H3PO4 and NaH2PO4 C) HCl and NaCl D) NaOH and NH3 E) NH3 and HC2H3O2 (acetic acid) The most nearly neutral solution

NH3 and HC2H3O2 (acetic acid)

A) NH3 and NH4Cl B) H3PO4 and NaH2PO4 C) HCl and NaCl D) NaOH and NH3 E) NH3 and HC2H3O2 (acetic acid) A buffer at a pH > 8

NH3 and NH4Cl