AP Chemistry Unit 2 Exam

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

(B) Na+

Which of the substances listed above has the highest boiling point, and why? (A) Ne, because its atoms have the largest radius (B) C2H6, because each molecule can form multiple hydrogen bonds (C) HF, because its molecules form hydrogen bonds (D) CH4, because its molecules have the greatest London dispersion forces

(C) HF, because its molecules form hydrogen bonds

The photoelectron spectra of the 1s electrons of two isoelectronic species, Ca2+ and Ar, are shown below . Which of the following correctly identifies the species associated with peak X and provides a valid justification? (2016) (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) Ca2+, because its nucleus has two more protons than the nucleus of Ar has

A student is given a sample of a pure, white crystalline substance. Which of the following would be most useful in providing data to determine if the substance is an ionic compound? (A) Examining the crystals of the substance under microscope (B) Determining the density of the substance (C) Testing the electrical conductivity of the crystals (D) Testing the electrical conductivity of an aqueous solution of the substance

(D) Testing the electrical conductivity of an aqueous solution of the substance

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

A.

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

A.

Based on the data in the tables below, which of the following statements provides the best prediction for the boiling point of NaCl? NaF MgO Boiling point (degrees C) 1695 3600 Na+ Mg2+ F- Cl- O2- Ionic radius (pm) 76 72 133 181 140 A. NaCl will have a lower boiling point than NaF because the coulombic attractions are weaker in NaCl than in NaF. B. NaCl will have a boiling point between that of NaF and MgO because the covalent character of the bonds in NaCl is intermediate between that of MgO and NaF. C. NaCl will have a higher boiling point than MgO because the ions are spaced farther apart in NaCl. D. NaCl will have a higher boiling point than MgO because the energy required to transfer electrons from the anion to the cation is larger in NaCl than in MgO.

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

Which of the following Lewis electron-dot diagrams represents the molecule that contains the smallest bond angle?

B

Steel is an alloy consisting of Fe with a small amount of C. Elemental Cr can be added to steel to make the steel less likely to rust; Cr atoms react with oxygen in the air to form a nonreactive layer of chromium oxide on the surface of the steel, preventing the oxidation of underlying Fe atoms. A sample of steel-chromium alloy contains 15% Cr by mass. Which of the following diagrams best shows a particle-level view of a surface section and an interior section of the alloy represented below at left? (The atomic radii of the atoms involved are given in the table below at right.)

B.

Which of the following Lewis diagrams represents a molecule that is polar?

B.

Based on the Lewis electron-dot diagram for NH3 shown above, the H-N-H bond angle is closest to which of the following? A. 120 degrees B. 109.5 degrees C. 90 degrees D. 60 degrees

B. 109.5 degrees

The figure above shows that in solid hydrogen fluoride there are two different distances between H atoms and F atoms. Which of the following best accounts for the two different distances? A. Accommodation of the necessary bond angles in the formation of the solid. B. Difference in strength between covalent bonds and intermolecular forces. C. Different isotopes of fluorine present in the samples. D. Uneven repulstions among nonbonding electron pairs.

B. Difference in strength between covalent bonds and intermolecular forces.

Compound Molar Mass (grams/mol) Na2O 62.0 MgO 40.3 K2O 94.2 CaO 56.1 According to the information in the table above, a 1.00 g sample of which of the following contains the greatest mass of oxygen? (2014) A. Na2O B. MgO C. K2O D. CaO

B. MgO

Which of the following claims about a binary compound in which the bonding is ionic is most likely to be scientifically correct? A. Both elements in the compound are metals. B. The electronegativity difference between the elements in the compound is relatively large. C. The atomic masses of the elements in the compound are relatively small. D. There is an equal sharing of electrons between the atoms of the elements in the compound.

B. The electronegativity difference between the elements in the compound is relatively large.

The particles in solid KI(s), a stable ionic compound, are arranged to maximize coulombic attractions while minimizing coulombic repulsions among the particles. Which of the following diagrams best represents the structure of solid KI?

C.

Which of the following particulate-level diagrams best represents an interstitial alloy?

C.

Which of the diagrams above best represents the CH2O molecule, and why? A. Diagram 1, because all bond angles are 180o. B. Diagram 1, because all atoms have a formal charge of 0. C. Diagram 2, because all atoms have a formal charge of 0. D. Diagram 2, because the molecule has a trigonal pyramidal shape.

C. Diagram 2, because all atoms have a formal charge of 0.

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 ?(2014) X2, Y2 Z2 A. H2 O2 N2 B. N2 O2 H2 C. H2 N2 O2 D. O2 H2 N2

C. H2 N2 O2

Molten (liquid) NaCl is represented by the particulate diagram shown above. Which of the following indicates whether NaCl (l) conducts electricity and best explains why or why not? A. It conducts electricity because Na is a metal. B. It does not conduct electricity because Cl is a nonmetal. C. It conducts electricity because ions are free to move. D. It does not conduct because there are no free electrons.

C. It conducts electricity because ions are free to move.

Based on formal charges, which of the following is the best Lewis electron-dot diagram for H3NO ?

D.

Which of the following correctly identifies which has the higher first ionization energy, Cl or Ar, and supplies the best justification? A. Cl, because of its higher electronegativity. B. Cl, because of its higher electron affinity. C. Ar, because of its completely filled valence shell. D. Ar, because of its higher effective nuclear charge.

D. Ar, because of its higher effective nuclear charge.

Which of the following correctly compares the strength of the two carbon-to-carbon bonds in the molecule represented in the Lewis electron-dot diagram above? A. The carbon-to-carbon bonds are the same strength because the C-C-C bond angles is 180o. B. The carbon-to-carbon bonds are the same strength because they are both bonds between carbon atoms. C. The carbon-to-carbon bond on the right is stronger because there are more hydrogen atoms attached to the rightmost carbon atom than to the leftmost carbon atom. D. The carbon-to-carbon bond on the left is stronger because it is a double bond.

D. The carbon-to-carbon bond on the left is stronger because it is a double bond.

The BF3 molecule is non polar, whereas the NF3 molecule is polar. Which of the following statements correctly accounts for the difference in polarity of the two molecules?(2014) A. In NF3, each F is joined to N with multiple bonds, whereas in BF3, each F is joined to B with single bonds. B. N-F bonds are polar, whereas B-F bonds are nonpolar. C. NF3 is an ionic compound, whereas BF3 is a molecular compound. D. Unlike BF3, NF3 has a nonplanar geometry due to an unshared pair of electrons on the N atom.

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

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. F2 < O2 < N2

Ba2+(aq) + SO42- → BaSO4(s) A student obtains a 5.0g sample of white powder labeled as BaCl2. After completely dissolving the powder in 25.0 mL of distilled water, the student adds excess Na2SO4(s) which causes a precipitate of BaSO4(s) to form, as represented by the equation above.The student filters the BaSO4(s), rinses it, and dries it until its mass is constant. Which of the following scientific questions could best be answered based on the results of the experiment? a. Is the BaCl2 (s) used in the experiment pure? b. What is the molar solubility of BaCl2 in water? c. What is the molar solubility of BaSO4 in water? d. Is the Na2SO4(s) used in the experiment pure?

a. Is the BaCl2 (s) used in the experiment pure?

The potential energy of a system of two atoms as a function of their intermolecular distance is shown in the diagram above. Which of the following is true regarding forces between the atoms when their intermolecular distance is x? a. The attractive and repulsive forces are balanced, so the atoms will remain an average internuclear distance x. b. There is a net repulsive force pushing the atoms apart, so the atoms will move further apart. c. There is a net attractive force pulling the atoms together, so the atoms will move closer together.. d. It cannot be determined whether the forces between the atoms are balanced, attractive, or repulsive, because the diagram shows only the potential energy.

a. The attractive and repulsive forces are balanced, so the atoms will remain an average internuclear distance x.

On the basis of electronegativity differences between atoms, which of the following scientific claims is the most accurate regarding the bonding in Mg(NO3)2? a. The is ionic bonding between Mg2+ and NO3- ions. b. There is polar covalent bonding between Mg and N atoms. c. There is polar covalent bonding between Mg and O atoms. d. There is ionic bonding between N5+ ions and O2- ions.

a. The is ionic bonding between Mg2+ and NO3- ions.

Which of the Lewis electron-dot diagrams for CO2 shown above is the more likely structure of CO2, and why? a. Diagram 1, because the double bonds are stronger than triple bonds. b. Diagram 1, because all the atoms have formal charge of 0. c. Diagram 2, because all the atoms have formal charge of 0. d. Diagram 2, because triple bonds are stonger than double bonds.

b. Diagram 1, because all the atoms have formal charge of 0.

Which of the following best indicates whether the solid substance represented by the particulate diagram shown above conducts electricity and explains why or why not? a. It conducts electricity because it is made of positive and negative particles. b. It conducts electricity because electrons are free to move through the substance. c. It does not conduct electricity because electrons are strongly attracted to specific positive particles. d. It does not conduct electricity because positive particles are not free to move through the substance.

b. It conducts electricity because electrons are free to move through the substance.

M+ is an unknown metal cation with a +1 charge. A student dissolves the chloride of the unknown metal, MCl, in enough water to make 100.0mL of solution. The student then mixes the solution with excess AgNO3 solution, causing AgCl to precipitate. The student collects the precipitate by filtration, dries it, and records the data shown below. (The Molar Mass of AgCl is 143 g/mol.) Mass of Unknown chloride, MCl 0.74g Mass of filter paper 0.80g Mass of filter paper plus AgCl precipitate 2.23g What is the identity of the metal chloride? a. NaCl b. KCl c. CuCl d. LiCl

b. KCl

Complete combustion of a sample of a hydrocarbon in excess oxygen produces equimolar quantities of carbon dioxide and water. Which of the following could be the molecular formula of the compound? a. C2H2 b. C2H6 c. C4H8 d. C6H6

c. C4H8

The mass spectrum represented above is most consistent with which of the following elements? a. Dy b. Eu c. Gd d. Tb

c. Gd

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? a. Polar covalent bond b. Nonpolar covalent bond c. Hydrogen bond d. London dispersion forces

c. Hydrogen bond

At room temperature I2(s) is a molecular solid. Which of the following provides a characteristic of I2(s) 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. It is not a good conductor of electricity because its valence electrons are localized in bonding and nonbonding pairs.

Which of the following claims about a binary compound composed of elements with the same electronegativity is most likely to be true? a. The compound has properties similar to those of both elements. b. The boiling point of the compound is above 1000oC. c. The bonding in the compound is nonpolar covalent. d. The compound contains ionic bonds.

c. The bonding in the compound is nonpolar covalent.

The table below shows the first ionization energy and atomic radius of several elements. Element First Ionization energy (kJ/mol) Atomic Radius (pm) B 801 85 C 1086 77 N 1400 75 O 1314 73 F 1680 72 Ne 2080 70 Which of the following best helps to explain the deviation of the first ionization energy of oxygen from the overall trend? a. The atomic radius of oxygen is greater than the atomic radius of fluorine. b. The atomic radius of oxygen is less than the atomic radius of nitrogen. c. There is repulsion between paired electrons in oxygen's 2p orbitals. d. There is attraction between paired electrons in oxygen's 2p orbitals.

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

Based on the ionization energies of element X given in the table below, which of the following is most likely the empirical formula of an oxide of element X? Ionization Energy (kJ/mol) First 577 Second 1,816 Third 2,745 Fourth 11,577 Fifth 14,482 a. XO2 b. X2O c. X2O3 d. X2O5

c. X2O3

The diagram above best illustrates which of the following phenomena associated with solids that have metallic bonding? a. Electrical conductivity, because it shows a lattice of positive ions immersed in a sea of electrons. b. Heat conductivity, because it shows how layers of atoms can slide past one another, creating friction between layers and causing the temperature of the solid to increase. c. The ability to form substitutional alloys, because it shows how atoms of two different metals can combine in a one-to-one ratio. d. Malleability, because it shows how adjacent layers of positive ions move relative to one another while remaining in full contact with the electron sea.

d. Malleability, because it shows how adjacent layers of positive ions move relative to one another while remaining in full contact with the electron sea.

Based on the diagrams above, which of the following best helps to explain why MgO(s) is not able to conduct electricity, but MgO(l) is a good conductor of electricity? a. MgO(s) does not contain free electrons, but MgO(l) contains free electrons that can flow. b. MgO(s) contains no water, but MgO(l) contains water that can conduct electricity. c. MgO(s) consists of separate Mg2+ ions and O2− ions, but MgO(l) contains MgO molecules that can conduct electricity. d. MgO(s) consists of separate Mg2+ ions and O2− ions held in a fixed lattice, but in MgO(l) the ions are free to move and conduct electricity.

d. MgO(s) consists of separate Mg2+ ions and O2− ions held in a fixed lattice, but in MgO(l) the ions are free to move and conduct electricity.

in the reaction represented above, what is the hybridization of the C atoms before and after the reaction occurs? Before After a. sp sp2 b. sp sp3 c. sp2 sp d. sp2 sp3

d. sp2 sp3