AP Chem final exam

In 1.00 mol of potassium zirconium sulfate trihydrate, K4Zr(SO4)4 • 3 H2O, there are

4 × 6.02 × 10^23 potassium atoms

Of the following compounds, which is the most ionic?

CaCl2

The complete photoelectron spectrum for an element is shown above. Which of the following observations would provide evidence that the spectrum is consistent with the atomic model of the element?

In its compounds, the element tends to form ions with a charge of +1.

The lattice energy of a salt is related to the energy required to separate the ions. For which of the following pairs of ions is the energy that is required to separate the ions largest? (Assume that the distance between the ions in each pair is equal to the sum of the ionic radii.)

Mg2+ and O2-

The mass spectrum of element X is presented in the diagram above. Based on the spectrum, which of the following can be concluded about element X?

The atomic mass of X is between 90 and 92.

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

1.2 x 1023

Which of the following ground-state electron configurations represents the atom that has the lowest first-ionization energy?

1s2 2s2 2p6 3s1

A sample of carbonate rock is a mixture of CaCO3 and MgCO3. The rock is analyzed in a laboratory, and the results are recorded in the table above. Which columns in the table provide all the information necessary to determine the mole ratio of Ca to Mg in the rock?

3,4,6,7

Which of the following is closest to the frequency of the light with photon energy of 3.3×10−19J?

5.0 x 10^14 s^-1

Approximately what mass of CuSO4 • 5H2O (250 g mol-1) is required to prepare 250 mL of 0.10 Mcopper(II) sulfate solution?

6.2g

The ionization energies for element X are listed in the table above. On the basis of the data, element Xis most likely to be

Al

If Na reacts with chlorine to form NaCl, which of the following elements reacts with Na to form an ionic compound in a one-to-one ratio, and why?

Br, because it has the same number of valence electrons as Cl.

The table above shows the structural formulas and molar masses for three different compounds. Which of the following is a list of the compounds in order of increasing boiling points?

Butane < acetone < 1-propanol

Based on the data in the table above, which of the following liquid substances has the weakest intermolecular forces?

CH3OH

A sample of a compound that contains only the elements C, H, and N is completely burned in O2 to produce 44.0 g of CO2, 45.0 g of H2O, and some NO2 . A possible empirical formula of the compound is

CH5N

Which of the following is a nonpolar molecule that contains polar bonds?

CO2

A student obtains a sample of a pure solid compound. In addition to Avogadro's number, which of the following must the student know in order to determine how many molecules are in the sample?

Molar mass of the compound, mass of the sample

Refer to the following gaseous molecules: (A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 Is the molecule in which the intramolecular forces are strongest

N2

The effective nuclear charge experienced by the outermost electron of Na is different than the effective nuclear charge experienced by the outermost electron of Ne. This difference best accounts for which of the following?

Na has a lower first ionization energy than Ne.

Resonance is most commonly used to describe the bonding in molecules of which of the following?

O3

Nonane and 2,3,4-trifluoropentane have almost identical molar masses, but nonane has a significantly higher boiling point. Which of the following statements best helps explain this observation?

The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane.

The diagrams above show the ultraviolet absorption spectra for two compounds. Diagram 1 is the absorption spectrum of pure acetone, a solvent used when preparing solutions for an experiment. Diagram 2 is the absorption spectrum of the solute for which the absorbance needs to be measured to determine its concentration. When the student reads the absorbance of the solution at 280nm, the result is too high. Which of the following is most likely responsible for the error in the measured absorbance?

The student forgot to calibrate the spectrophotometer first by using a cuvette containing only acetone.

Which of the following best helps to explain why the electron affinity of Br has a greater magnitude than that of I?

There is a greater attraction between an added electron and the nucleus in Brthan in I.

The student made the standard curve above. Which of the following most likely caused the error in the point the student plotted at 0.050MCo2+(aq) ?

There was distilled water in the cuvette when the student put the standard solution in it.

The BF3 molecule is nonpolar, whereas the NF3 molecule is polar. Which of the following statements accounts for the difference in polarity of the two molecules?

Unlike BF3, NF3 has a nonplanar geometry due to an unshared pair of electrons on the N atom.

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 represents an electron configuration that corresponds to the valence electrons of an element for which there is an especially large jump between the second and third ionization energies? (Note: n represents a principal quantum number equal to or greater than 2.)

ns2

H - C ≡ C - H What is the hybridization of the carbon atoms in a molecule of ethyne, represented above?

sp

A solution of methanol, CH3OH, in water is prepared by mixing together 128 g of methanol and 108 g of water. The mole fraction of methanol in the solution is closest to

0.40

Which of the following numerical expressions gives the number of particles in 2.0g of Ne?

2.0g/20.18g/mol(6.0x10^23 particles/mol)

Based on periodic trends 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?

242 pm, 419 kJ/mol

The figure above represents three sealed 1.0 L vessels, each containing a different inert gas at 298 K. The pressure of Ar in the first vessel is 2.0 atm. The ratio of the numbers of Ar, Ne, and He atoms in the vessels is 2:1:6, respectively. After all the gases are combined in a previously evacuated 2.0 L vessel, what is the total pressure of the gases at 298 K?

4.5 atm

Based on their Lewis diagrams, which of the following pairs of liquids are most soluble in each other?

A

The gas particles in vessel 3 at 27°C are represented in the diagram above. The lengths of the arrows represent the speeds of the particles. Which of the following diagrams best represents the particles when vessel 3 is heated to 127°C?

A

The potential energy as a function of internuclear distance for three diatomic molecules, X2, Y2, and Z2, is shown in the graph above. Based on the data in the graph, which of the following correctly identifies the diatomic molecules, X2, Y2, and Z2?

A

Which of the following diagrams best depicts an alloy of Ni and B?

A

Which of the following diagrams best illustrates how a displacement in an ionic crystal results in cleavage and brittleness?

A

The pressure, in atm, exerted by 1.85 mol of an ideal gas placed in a 3.00 L container at 35.0°C is given by which of the following expressions?

A (1.85)(0.0821)(308)/(3.00) atm

The mass spectrum of the element Sb is most likely represented by which of the following?

B

Which of the following shows the correct number of protons, neutrons, and electrons in a neutral cesium-134 atom?

B

(A) H2O(B) NH3(C) BH3(D) CH4(E) SiH4 Has a central atom with less than an octet of electrons

BH3

(A) H2O(B) NH3(C) BH3(D) CH4(E) SiH4 Is predicted to have the largest bond angle

BH3

Under which of the following conditions of temperature and pressure would 1.0 mol of the real gas CO2(g) behave most like an ideal gas?

C Temp 800 Pressure .1

The elements in which of the following have most nearly the same atomic radius?

Cr, Mn, Fe, Co

The diagram above represents the absorption spectrum for a pure molecular substance. Which of the following correctly indicates the type of transition observed for the substance in each of the regions of the absorption spectrum?

D

Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains only one electron in the highest occupied energy sublevel

Ga

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 center of the tube?

HCl and CH3NH2

Which of the following correctly indicates whether the solid represented by the particulate model shown above conducts electricity and explains why or why not?

It does not conduct electricity because its ions cannot move freely within the solid.

1s2 2s2 2p6 3s2 3p3 Atoms of an element, X, have the electronic configuration shown above. The compound most likely formed with magnesium, Mg, is

Mg3X2

Has molecules with a pyramidal shape

NH3(g)

Which of the following compounds contains both ionic and covalent bonds?

NH4Cl

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?

P atoms introduce additional mobile positive charges.

Which of the following has a zero dipole moment?

PF5

Refer to the following gaseous molecules: (A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 Is a polar molecule

SO2

Refer to the following gaseous molecules: (A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 Is best represented by two or more resonance forms

SO2

The photoelectron spectrum for the element nitrogen is represented above. Which of the following best explains how the spectrum is consistent with the electron shell model of the atom?

The electrons in the 2p sublevel have the smallest binding energy.

In a paper chromatography experiment, a sample of a pigment is separated into two components, X and Y, as shown in the figure above. The surface of the paper is moderately polar. What can be concluded about X and Y based on the experimental results?

Y is more polar than X.

Lewis electron-dot diagrams for CO2 and SO2 are given above. The molecular geometry and polarity of the two substances are

different because S has a greater number of electron domains (regions of electron density) surrounding it than C has

The best explanation for the lower pressure in container 4 is that SO2 molecules

have stronger intermolecular attractions than the other three gases

Which of the following is the strongest type of interaction that occurs between the atoms within the circled areas of the two molecules represented above?

hydrogen bond

According to the VSEPR model, the progressive decrease in the bond angles in the series of molecules CH4, NH3, and H2O is best accounted for by the

increasing number of unshared pairs of electrons

A certain crystalline substance that has a low melting point does not conduct electricity in solution or when melted. This substance is likely to be

molecular solid