AP Chemistry Exam Review

1s2 2s2 2p6 3s2 3p6 How many unpaired electrons are in the atom represented by the electron configuration above? A. 0 B. 1 C. 2 D. 3

A. 0

The photoelectron spectrum for the element boron is represented above. Which of the following best explains how the spectrum is consistent with the electron shell model of the atom? A. The spectrum shows an odd number electrons. B. The spectrum shows a single electron in the 2p subshell. C. The spectrum shows equal numbers of electrons in the first and second electron shells. D. The spectrum shows three electrons with the same binding energy in the second electron shell.

B. The spectrum shows a single electron in the 2p subshell.

A 1.0 mol sample of which of the following compounds has the greatest mass? A.NO B. NO2 C. N2O D. N2O5

D. N2O5

Which of the following correctly compares the strength of the two carbon-to-carbon bonds in the molecule represented in the Lewis diagram shown above? A. The carbon-to-carbon bond on the left is stronger because it is a double bond. B. The carbon-to-carbon bonds are the same strength because the C-C-CC-C-C bond angle is 180°180°. C. The carbon-to-carbon bonds are the same strength because they are both bonds between carbon atoms. D. 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.

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

In a lab a student is given a 21 g sample of pure Cu metal. Which of the following pieces of information is most useful for determining the number of Cu atoms in the sample? Assume that the pressure and temperature in the lab are 1.0 atm and 25°C. A. The molar mass of Cu. B. The density of Cu at 25°C. C. The volume of the Cu sample D. The ratio of the two main isotopes found in pure Cu

A. The molar mass of Cu.

A vessel contains a mixture of gases. The mass of each gas used to make the mixture is known. Which of the following information is needed to determine the mole fraction of each gas in the mixture? A. The molar mass of each gas B. The density of the gases in the vessel C. The total pressure of the gases in the vessel D. The number of atoms per molecule for each gas

A. The molar mass of each gas

Which of the Lewis diagrams shown above is the more likely structure of CO2, and why? A.Diagram 1, because all the atoms have a formal charge of 0. B. Diagram 1, because double bonds are stronger than triple bonds. C. Diagram 2, because all the atoms have a formal charge of 0. D. Diagram 2, because triple bonds are stronger than double bonds

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

Which of the following numerical expressions gives the number of moles in 5.0g of CaO? A.5.0g × 56 g/mol B. 5.0g /56 g/mol C.56g/mol /5.0g D. 1/5.0g × 1/56 g/mol

B. 5.0g /56 g/mol

The mass spectrum for an unknown element is shown above. According to the information in the spectrum, the atomic mass of the unknown element is closest to A. 90 amu B. 91 amu C. 93 amu D. 94 amu

B. 91 amu

The particulate-level diagram shown above best helps to explain which of the following properties of ionic solids? A. Density B. Brittleness C. Malleability D. Conductivity

B. Brittleness

Rb reacts with O in a mole ratio of 2 to 1, forming the ionic compound Rb2O. Which of the following elements will react with O in a mole ratio of 2 to 1, forming an ionic compound, and why? A. S, because it is in the same group as O. B. Cs, because it is in the same group as Rb. C. Sr, because it is in the same period as Rb. D. Br because the atomic mass of Br is similar to that of Rb.

B. Cs, because it is in the same group as Rb.

The mass spectrum represented above is most consistent with which of the following elements? A. Eu B. Gd C. Tb D. Dy

B. Gd

Which of the following 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 the positive particles are not free to move through the substance.

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

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 conducts electricity because ions are free to move. C. It does not conduct electricity because Cl is a nonmetal. D. It does not conduct electricity because there are no free electrons.

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

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. Malleability, because it shows how adjacent layers of positive ions can move relative to one another while remaining in full contact with the electron sea. C. 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. D. The ability to form substitutional alloys, because it shows how atoms of two different metals can combine in a one-to-one ratio.

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

A jar labeled NaCl contains a powder. The table above contains information determined by analyzing a sample of the powder in the laboratory. What information in the table is the most helpful in determining whether the powder is pure NaCl? A. Mass B. Mass percent of Na C. Density D. Color

B. Mass percent of Na

The complete photoelectron spectrum of an element is given above. Which labeled peak corresponds to the 1s electrons and why? A. Peak X, because 1s electrons are the easiest to remove from the atom. B. Peak X, because 1s electrons have the strongest attractions to the nucleus. C. Peak Y, because electrons in the 1s sublevel are the farthest from the nucleus. D. Peak Y, because there are fewer electrons in an ss sublevel than in a p sublevel.

B. Peak X, because 1s electrons have the strongest attractions to the nucleus.

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 bonding in the compound is nonpolar covalent. C. The boiling point of the compound is above 1000°C. D. The compound contains strong ionic bonds.

B. The bonding in the compound is nonpolar covalent.

A student obtains a mixture of the chlorides of two unknown metals, X and Z. The percent by mass of X and the percent by mass of Z in the mixture is known. Which of the following additional information is most helpful in calculating the mole percent of XCl(s) and of ZCl(s) in the mixture? A. The number of isotopes of Cl B. The molar masses of X and Z C. The density of either XCl(s) or ZCl(s). D. The percent by mass of Cl in the mixture

B. The molar masses of X and Z

The complete photoelectron spectrum of the element carbon is represented above. Which of the following best explains how the spectrum is consistent with the electron shell model of the atom? A. The spectrum shows four electrons in the inner electron shell. B. The spectrum shows equal numbers of electrons in the three occupied electron subshells. C. The spectrum shows that all the electrons in the valence shell have the same binding energy. D. The spectrum shows more electrons in the inner electron shell than in the outer electron shell.

B. The spectrum shows equal numbers of electrons in the three occupied electron subshells.

A student measures the mass of a sample of a metallic element, M. Then the student heats the sample in air, where it completely reacts to form the compound MO. The student measures the mass of the compound that was formed. Which of the following questions can be answered from the results of the experiment? A. What is the density of M? B. What is the molar mass of M? C. What is the melting point of M? D. What is the melting point of MO?

B. What is the molar mass of M?

What charge does Al typically have in ionic compounds, and why? A. +1, because in the ground state it has one unpaired electron. B. +2, because it has two electrons in the 2s subshell. C. +3, because it has three valence electrons. D. +4, because it is in the fourth row of the periodic table.

C. +3, because it has three valence electrons.

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

C. 109.5°

Based on the mass spectrum of a pure element represented above, the average atomic mass of the element is closest to which of the following? A. 185.7amu B.186.0 amu C. 186.3 amu D.186.9 amu

C. 186.3 amu

Which of the following is the correct electron configuration for a ground-state atom of magnesium (atomic number 12) ? A. 1s2 2s2 2p8 B. 1s2 2s2 3s2 3p6 C. 1s2 2s2 2p6 3s2 D. 1s2 2s2 3s4 3p4

C. 1s2 2s2 2p6 3s2

The atomic radii of the elements in the nitrogen group in the periodic table are given in the table above. Which of the following best helps explain the trend of increasing atomic radius from N to Bi? A. The number of particles in the nucleus of the atom increases. B. The number of electrons in the outermost shell of the atom increases. C. The attractive force between the valence electrons and the nuclei of the atoms decreases. D. The repulsive force between the valence electrons and the electrons in the inner shells decreases.

C. The attractive force between the valence electrons and the nuclei of the atoms decreases.

Which of the following best helps explain why the first ionization energy of K is less than that of Ca? A. The electronegativity of K is greater than that of Ca. B. The atomic radius of the K atom is less than that of the Ca atom. C. The valence electron of K experiences a lower effective nuclear charge than the valence electrons of Ca. D. The nucleus of the K atom has fewer neutrons, on average, than the nucleus of the Ca atom has.

C. The valence electron of K experiences a lower effective nuclear charge than the valence electrons of Ca.

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

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

Which of the following best helps explain why an atom of Rb gas more easily loses an electron in a chemical reaction than an atom of Li gas? A. Rb has a higher electronegativity than Li has. B. The Rb atom has a greater number of valence electrons than the Li atom has. C. The nucleus of the Rb atom has a greater number of protons and neutrons than the nucleus of the Li atom has. D. In the Rb atom the valence electron is farther from its nucleus than the valence electron of Li is from its nucleus.

D. In the Rb atom the valence electron is farther from its nucleus than the valence electron of Li is from its nucleus.

Which of the following best helps to explain why the atomic radius of K is greater than that of Br? A. The first ionization energy of K is higher than that of Br. B. The valence electrons in K are in a higher principal energy level than those of Br. C. In the ground state, an atom of K has fewer unpaired electrons than an atom of Br has. D. The effective nuclear charge experienced by valence electrons is smaller for K than for Br.

D. The effective nuclear charge experienced by valence electrons is smaller for K than for Br.

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

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

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(s) ? A. There is polar covalent bonding between Mg atoms and N atoms. B. There is polar covalent bonding between Mg atoms and O atoms. C. There is ionic bonding between N5+ ions and O2− ions. D. There is ionic bonding between Mg2+ ions and NO3− ions.

D. There is ionic bonding between Mg2+ ions and NO3− ions.

A 42.0g sample of compound containing only C and H was analyzed. The results showed that the sample contained 36.0g of C and 6.0g of H. Which of the following questions about the compound can be answered using the results of the analysis? A. What was the volume of the sample? B. What is the molar mass of the compound? C. What is the chemical stability of the compound? D. What is the empirical formula of the compound?

D. What is the empirical formula of the compound?