AP Chemistry Final Exam Practice Multiple Choice

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

110 mL

. . . 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

12

Which of the following diatomic species has a bond order of 2? Li2 B2 N2 O2 F2

O2 (O2 has a double bond)

Which of the following molecules has an angular (bent) geometry that is commonly represented as a resonance hybrid of two or more electron-dot structures? CO2 O3 CH4 BeF2 OF2

O3

Of the following, the best explanation for the fact that most gases are easily compressed is that the molecules in a gas

are relatively far apart

Which of the following properties generally decreases across the periodic table from sodium to chlorine?

atomic radius

Nitramide, N2H2O2, decomposes slowly in aqueous solution. This decomposition is believed to occur according to the reaction mechanism above. What is the rate law?

k[N2H2O2]/[H+]

Relatively slow rates of chemical reaction are associated with which of the following?

strong bonds in reactant molecules

The cooling curve above shows how the temperature of a sample varies with time as the sample goes through phase changes. The sample starts as a gas, and heat is removed at a constant rate. At which time does the sample contain the most liquid?

t4

The geometry of the SO3 molecule is best described as

trigonal planar

How many carbon atoms are contained in 2.8 g of C2H4 ?

1.2 x 10^23

3 C2H2(g) → C6H6(g) What is the standard enthalpy change ΔHo, for the reaction represented above? (ΔHof of C2H2(g) is 230 kJ mol-1; (ΔHof of C6H6(g) is 83 kJ mol-1;)

-607 kJ

The oxidation of iodide ions by arsenic acid in acidic aqueous solution occurs according to the stoichiometry shown above. The experimental rate law of the reaction is: Rate = k[H3AsO4] [I-] [H3O+] What is the order of the reaction with respect to I-?

1

Of the following electron configurations of neutral atoms, which represents an atom in an excited state? 1s2 2s2 2p5 1s2 2s2 2p5 3s2 1s2 2s2 2p6 3s1 1s2 2s2 2p6 3s2 3p6 1s2 2s2 2p6 3s2 3p5

1s2 2s2 2p5 3s2

NO(g) and O2(g) react to form NO2(g). The rate law of the reaction is rate=k[NO]2[O2]. If the reaction occurs in a single elementary step that is a three-body molecular collision, then which of the following is the equation for the elementary step?

2NO + O2 --> 2NO2

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.)

3 atm

(A) A network solid with covalent bonding (B) A molecular solid with zero dipole moment (C) A molecular solid with hydrogen bonding (D) An ionic solid (E) A metallic solid Solid ethyl alcohol, C2H5OH

A molecular solid with hydrogen bonding

Which is a precipitation reaction? (A) H2SeO4(aq) + 2 Cl-(aq) + 2 H+(aq) → H2SeO3(aq) + Cl2(g) + H2O(l) (B) S8(s) + 8 O2(g) → 8 SO2(g) (C) 3 Br2(aq) + 6 OH-(aq) → 5 Br-(aq) + BrO3-(aq) + 3 H2O(l) (D) Ca2+(aq) + SO42-(aq) → CaSO4(s) (E) PtCl4(s) + 2 Cl-(aq) → PtCl62-(aq)

Ca2+(aq) + SO42-(aq) → CaSO4(s)

Of the following compounds, which is the most ionic? SiCl4 BrCl PCl3 Cl2O CaCl2

CaCl2

Step 1: Ce4+ + Mn2+ → Ce3+ + Mn3+ Step 2: Ce4+ + Mn3+ → Ce3+ + Mn4+ Step 3: Mn4+ + Tl+ → Tl3+ + Mn2+ The proposed steps for a catalyzed reaction between Ce4+ and Tl+ are represented above. The products of the overall catalyzed reaction are

Ce2+ and TI3+

In which of the following process are covalent bonds broken? I2(s) → I2(g) CO2(s) → CO2(g) NaCl(s) → NaCl(l) C(diamond) → C(g) Fe(s) → Fe(l)

C(diamond) → C(g)

Sodium chloride is LEAST soluble in which of the following liquids? H2O CCl4 HF CH3OH CH3COOH

CCl4

Which of the following describes the changes in forces of attraction that occur as H2O changes phase from a liquid to a vapor?

Hydrogen bonds between H2O molecules are broken

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.

I and II only

Factors that affect the rate of a chemical reaction include which of the following? I. Frequency of collisions of reactant particles II. Kinetic energy of collisions of reactant particles III. Orientation of reactant particles during collisions

I, II, and II

Equal masses of three different ideal gases, X, Y, and Z, are mixed in a sealed rigid container. If the temperature of the system remains constant, which of the following statements about the partial pressure of gas X is correct?

It depends on the relative molecular masses of X,Y, and Z

On the basis of the solubility curves shown above, the greatest percentage of which compound can be recovered by cooling a saturated solution of that compound from 90°C to 30°C?

KNO3

Which of the following molecules has the shortest bond length? N2 O2 Cl2 Br2 I2

N2

Which of the following has the largest bond dissociation energy? Li2 B2 N2 O2 F2

N2 (because N2 has a triple bond, making it have the largest bond dissociation energy)

The electron-dot structure (Lewis structure) for which of the following molecules would have two unshared pairs of electrons on the central atom? H2S NH3 CH4 HCN CO2

NH3

Which of the following is the conjugate acid of NH2- ?

NH3

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?

P(He) < P(Ne) < P(Ar)

A possible mechanism for the overall reaction represented above is the following. NO(g) + NO(g) → N2O2(g) slow N2O2(g) + O2(g) → 2NO2(g) fast Which of the following rate expressions agrees best with this possible mechanism?

Rate = k[NO]2

A reaction was observed for 20 days and the percentage of the reactant remaining after each day was recorded in the table above. Which of the following best describes the order and the half-life of the reaction? 0 days- 100% left; 3 days-50%; 6 days-25%

Reaction order: First Half-life: 3

Which of the following gases deviates most from ideal behavior? SO2 Ne CH4 N2 H2

SO2

The dissolution of an ionic solute in a polar solvent can be imagined as occurring in three steps, as shown in the figure above. In step 1, the separation between ions in the solute is greatly increased, just as will occur when the solute dissolves in the polar solvent. In step 2, the polar solvent is expanded to make spaces that the ions will occupy. In the last step, the ions are inserted into the spaces in the polar solvent. Which of the following best describes the enthalpy change, ΔH, for each step?

Step 1 and 2 are endothermic, and the final step is exothermic

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?

The average speed of the gas molecules remains the same

A 1.0 g sample of a cashew was burned in a calorimeter containing 1000. g of water, and the temperature of the water changed from 20.0°C to 25.0°C. In another experiment, a 3.0 g sample of a marshmallow was burned in a calorimeter containing 2000. g of water, and the temperature of the water changed from 25.0°C to 30.0°C. Based on the data, which of the following can be concluded about the energy content for 1.0 g of each of the two substances? (The specific heat of water is 4.2 J/(g⋅°C).)

The combustion of 1.0 g of cashew releases more energy than the combustion of 1.0 g of marshmellow

A student prepared five solutions of CuSO4 with different concentrations, and then filled five cuvettes, each containing one of the solutions. The cuvettes were placed in a spectrophotometer set to the appropriate wavelength for maximum absorbance. The absorbance of each solution was measured and recorded. The student plotted absorbance versus concentration, as shown in the figure above. Which of the following is the most likely explanation for the variance of the data point for the 0.600 M CuSO4 solution?

The cuvette used for the 0.600 M solution had not been wiped clean before being put in the spectrophotometer

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?

The dehydrated sample absorbed moisture after heating

A 100 g sample of a metal was heated to 100oC and then quickly transferred to an insulated container holding 100 g of water at 22oC. The temperature of the water rose to reach a final temperature of 35oC. Which of the following can be concluded?

The metal temperature changed more than the water temperature did, but the metal lost the same amount of thermal energy as the water gained

A student pipetted five 25.00-milliliter samples of hydrochloric acid and transferred each sample to an Erlenmeyer flask, diluted it with distilled water, and added a few drops of phenolphthalein to each. Each sample was then titrated with a sodium hydroxide solution to the appearance of the first permanent faint pink color. The following results were obtained. Volumes of NaOH Solution First Sample.....35.22 mL Second Sample.....36.14 mL Third Sample.....36.13 mL Fourth Sample .....36.15 mL Fifth Sample.....36.12 mL Which of the following is the most probable explanation for the variation in the student's results?

The pipette was not rinsed with the HCl solution

NaCl(aq)+H2O(l) A student had two dilute, colorless solutions, HCl(aq) and NaOH(aq), which were at the same temperature. The student combined the solutions, and the reaction represented above occurred. Which of the following results would be evidence that a chemical reaction took place?

The temperature of the reaction mixture increases

The mass percent of carbon in pure glucose, C6H12O6, is 40.0 percent. A chemist analyzes an impure sample of glucose and determines that the mass percent of carbon is 38.2 percent. Which of the following impurities could account for the low mass percent of carbon in the sample?

Water, H2O