AP Chem Unit 4 Test Review

To make Au stronger and harder, it is often alloyed with other metals, such as Cu and Ag. Consider two alloys, one of Au and Cu and one of Au and Ag, each with the same mole fraction of Au. If the Au/Cu alloy is harder than the Au/Ag alloy, then which of the following is the best explanation based on the information in the table above?

Cu atoms are smaller than Ag atoms, thus they interfere more with the displacement of atoms in the alloy.

Based on the data in the table above, which of the following correctly predicts the relative strength of the attraction of Zn2+, Ca2+, and Ba2+ ions to water molecules in a solution, from strongest to weakest, and provides the correct reason?

Zn2+ > Ca2+ > Ba2+ because the smaller ions have a stronger coulombic attraction to water

The mass spectrum of an average sample of a pure element is shown in the figure above. Which of the following is the identity of the element? (90 longest, 92 and 94 short equal)

Zr

The complete photoelectron spectrum of an element is given above. Which of the following electron configurations is consistent with the spectrum?

1s2 2s2 2p6 3s2 3p3

Which of the following represents the ground state electron configuration for the Mn3+ ion? (Atomic number Mn = 25)

1s2 2s2 2p6 3s2 3p6 3d4

Which of the following best represents the ground-state electron configuration for an atom of selenium?

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4

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

Al

The first ionization energy of an element is the energy required to remove an electron from a gaseous atom of the element (i.e., X(g) → X+(g) + e−). The values of the first ionization energies for the third-row elements are shown in the graph above. On the basis of the information given, which of the following reactions is exothermic?

Al(g) + Mg+(g) → Al+(g) + Mg(g)

The first five ionization energies of an unknown element are listed in the table above. Which of the following statements correctly identifies the element and cites the evidence supporting the identification?

Al, because of the large difference between the third and fourth ionization energies

Which of the following correctly identifies which has the higher first-ionization energy, Cl or Ar, and supplies the best justification?

Ar, because of its higher effective nuclear charge

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

Atomic Radius

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

B(longer 121, shorter 123)

The first five ionization energies of a second-period element are listed in the table above. Which of the following correctly identifies the element and best explains the data in the table?

B, because it has three valence electrons

Atoms of Mg combine with atoms of F to form a compound. Atoms of which of the following elements combine with atoms of F in the same ratio?

Ba

(A) Cs(B) Ag(C) Pb(D) Br(E) Se Has the highest electronegativity

Br

When free Cl(g) atoms encounter O3(g) molecules in the upper atmosphere, the following reaction mechanism is proposed to occur. The proposed mechanism can be written in a more general form, as shown above. Species other than Cl can also decompose O3 through the same mechanism. Which of the following chemical species is most likely to decompose O3 in the upper atmosphere through the above mechanism?

Br

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 diagram above represents the photoelectric effect for a metal. When the metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3×10^−19J. Which of the following is closest to the frequency of the light with photon energy of 3.3×10^−19J?

C 5.0×10^14s−1

The compound CCl4 is nonflammable and was once commonly used in fire extinguishers. On the basis of the periodic properties, which of the following compounds can most likely be used as a fire-resistant chemical?

CBr4

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?

Ca2+, because its nucleus has two more protons than the nucleus of Ar has

Which of the following lists Mg, P, and Cl in order of increasing atomic radius?

Cl < P < Mg

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

Cr, Mn, Fe, Co

(A) Cs(B) Ag(C) Pb(D) Br(E) Se Has the lowest first-ionization energy

Cs

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

D 1s2 2s2 2p6 3s1

A student uses visible spectrophotometry to determine the concentration of CoCl2(aq) in a sample solution. First the student prepares a set of CoCl2(aq) solutions of known concentration. Then the student uses a spectrophotometer to determine the absorbance of each of the standard solutions at a wavelength of 510nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. A wavelength of 510nm510nm corresponds to an approximate frequency of 6×10^14s−1. What is the approximate energy of one photon of this light?

D 4×10^−19J

Which of the following is the electron configuration of an excited atom that is likely to emit a quantum of energy?

E 1s2 2s2 2p6 3s1 3p1

The complete photoelectron spectra of neutral atoms of two unknown elements, X and Y, are shown above. Which of the following can be inferred from the data?

Element Y has a greater nuclear charge than element X does.

Which of the following best helps to account for the fact that the F- ion is smaller than the O2- ion?

F- has a larger nuclear charge than O2- has.

The atom that contains only one electron in the highest occupied energy sublevel

Ga

The photoelectron spectra for HH and HeHe are represented above. Which of the following statements best accounts for the fact that the peak on the HeHe spectrum is farther to the left and higher than the peak on the HH spectrum?

He has a greater nuclear charge than H and an additional electron in the same energy level.

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

The mass spectrum of a sample of a pure element is shown above. Based on the data, the peak at 26amu represents an isotope of which of the following elements? (Long 24, shorter 25 26)

Mg with 14 neutrons

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

Which statement correctly compares what occurs when molecules absorb photons in the microwave region with what occurs when molecules absorb photons in the infrared region?

Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause electrons in the molecules to increase their electronic energy states.

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.

A sample containing atoms of C and F was analyzed using x-ray photoelectron spectroscopy. The portion of the spectrum showing the 1s peaks for atoms of the two elements is shown above. Which of the following correctly identifies the 1s peak for the F atoms and provides an appropriate explanation?

Peak X, because F has a greater nuclear charge than C has.

Based on the information above and periodic trends, which of the following is the best hypothesis regarding the oxide(s) formed by Rb?

Rb will form Rb2O, Rb2O2, and RbO2.

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?

Region X: Electronic transition Region Y: Molecular vibration Region Z: Molecular rotation

Forms monatomic ions with 2- charge in solutions

S

The atom that contains exactly two unpaired electrons

S

Based on Coulomb's law and the information in the table above, which of the following anions is most likely to have the strongest interactions with nearby water molecules in an aqueous solution?

S2-

Which of the following ions has the same number of electrons as Br - ?

Sr2+

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? (High 90, lower 92 and 94)

The atomic mass of X is between 90 and 92.

Which of the following correctly compares periodic properties of two elements and provides an accurate explanation for that difference?

The atomic radius of Cl is smaller than that of S because Cl has a larger nuclear charge than S does.

The energy required to dissociate an ionic solid into gaseous ions (lattice energy) for the compounds NaF and MgF2 is shown in the table above. On the basis of Coulomb's law, which of the following best helps to explain the large difference between the lattice energies of NaF and MgF2 ?

The charge of the Mg cation is larger than that of the Na cation.

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 2p2p sublevel have the smallest binding energy.

Which of the following best helps to explain why Na(s) is more reactive with water than Mg(s) is?

The first ionization energy of Na is less than that of Mg.

Beta-carotene is an organic compound with an orange color. The diagram above shows the ultraviolet spectrum of beta-carotene. Which of the following statements is true about the absorption bands in the spectrum?

The two main absorption bands are associated with transitions in electronic energy levels. The band in the region corresponding to shorter wavelengths shows a lower absorbance than the band in the region corresponding to longer wavelengths.

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

There is a greater attraction between an added electron and the nucleus in Br than in II.

The table above shows the first ionization energy and atomic radius of several elements. Which of the following best helps to explain the deviation of the first ionization energy of oxygen from the overall trend?

There is repulsion between paired electrons in oxygen's 2p orbitals.

N2 molecules absorb ultraviolet light but not visible light. I2 molecules absorb both visible and ultraviolet light. Which of the following statements explains the observations?

Visible light does not produce transitions between electronic energy levels in the N2 molecule but does produce transitions in the I2 molecule.

Based on the ionization energies of element X given in the table above, which of the following is most likely the empirical formula of an oxide of element X?

X2O3

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: nn represents a principal quantum number equal to or greater than 2.)

ns2

The particle-level diagram above represents the structure of solid KF. Although the molar mass of KCl is greater than that of KF, the density of KCl is actually less than that of KF. Which of the following representations of the structure of KCl best helps to explain this phenomenon?

plus minus plus, minus plus minus, plus minus plus

The elements K and Cl react directly to form the compound KCl according to the equation above. Refer to the information above and the table below to answer the questions that follow. Which of the following expressions is equivalent to ΔHo for the reaction represented above?

x+2y

Of the following electron configurations of neutral atoms, which represents an atom in an excited state?

1s2 2s2 2p5 3s2

Which of the following is the ground-state electron configuration of the F−ion?

1s2 2s2 2p6

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 diagram above represents the photoelectric effect for a metal. When the metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3×10^−19J? Using the wavelength information provided above, what is the color of the light?

B Orange

Infrared spectroscopy is a useful tool for scientists who want to investigate the structure of certain molecules. Which of the following best explains what can occur as the result of a molecule absorbing a photon of infrared radiation?

B The energies of infrared photons are in the same range as the energies associated with different vibrational states of chemical bonds. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing the types and strengths of different bonds in the molecules.

Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits each statement. A choice may be used once, more than once, or not at all in each set. (A) Cs(B) Ag(C) Pb(D) Br(E) Se Has the largest atomic radius

Cs

RbCl has a high boiling point. Which of the following compounds is also likely to have a high boiling point, and why?

CsCl, because its elements have very different electronegativities and it is an ionic compound.

The elements I and Te have similar average atomic masses. A sample that was believed to be a mixture of I and Te was run through a mass spectrometer, resulting in the data above. All of the following statements are true. Which one would be the best basis for concluding that the sample was pure Te?

I consists of only one naturally occurring isotope with 74 neutrons, whereas Te has more than one isotope.

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+(g) and O2−(g)

Which of the following elements has the mass spectrum represented above? (Long 98, then 96, 92 and 95 equal, 94 97 100 equal)

Mo

Which of the following elements has the largest first ionization energy?

N

Zn(s) is used to reduce other compounds in chemical reactions. If a chemist needs a substance that is more effective in its reducing ability, which of the following species would be the best choice?

Na

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?

Na+

Based on the data in the tables above, which of the following statements provides the best prediction for the boiling point of NaCl ?

NaCl will have a lower boiling point than NaF because the coulombic attractions are weaker in NaCl than in NaF .

The photoelectron spectra above show the energy required to remove a 1s electron from a nitrogen atom and from an oxygen atom. Which of the following statements best accounts for the peak in the upper spectrum being to the right of the peak in the lower spectrum?

Nitrogen atoms have a smaller nuclear charge than oxygen atoms.

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?

The electron removed during the third ionization is, on average, much closer to the nucleus than the first two electrons removed were.

Which of the following best helps explain why the electronegativity of Cl is less than that of F?

When Cl and F form bonds with other atoms, the Cl bonding electrons are more shielded from the positive Cl nucleus than the FF bonding electrons are shielded from the positive F nucleus.

The ionization energies of an unknown element, X, are listed in the table above. Which of the following is the most likely empirical formula of a compound formed from element X and phosphorus, P ?

X3P2

The elements K and Cl react directly to form the compound KCl according to the equation above. Refer to the information above and the table below to answer the questions that follow. Which of the values of ΔH° for a process in the table is (are) less than zero (i.e., indicate(s) an exothermic process) ?

y and z only