ap chem final tables/diagrams

The survival of aquatic organisms depends on the small amount of O2 that dissolves in H2O. The diagrams above represent possible models to explain this phenomenon. Which diagram provides the better particle representation for the solubility of O2 in H2O and why?

C. Diagram 2, because the polar H2O molecules can induce temporary dipoles on the electron clouds of O2 molecules.

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

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

When students added 2.0g of NaI crystals to 100.mL of Pb(NO3)2(aq), a yellow precipitate formed. After the solution was filtered, the yellow solid was dried and weighed. Data from the experiment are shown in the table above. Which of the following claims is best supported by the observations?

A chemical change occurred when a yellow, insoluble compound with a larger mass than the original NaI formed.

The diagrams above represent two allotropes of solid phosphorus. Which of the following correctly identifies the allotrope with the higher melting point and explains why?

B) Allotrope II, because it has covalent bonds between the phosphorous atoms that are stronger than the dispersion forces between the P4 molecules in allotrope I.

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

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?

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?

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.

(Li+, Mg2+, Na+, and Ca2+ cations shown above) The diagram above represents four cations, all shown to the same scale. Which cation would be predicted by Coulomb's law to have the strongest ion-dipole attraction to water, and why?

B) Mg2+, because it has the largest charge-to-size ratio.

The table above provides the values for some physical properties of H2S and H2O. Approximately, how many moles of H2S must be condensed to release as much heat as would be released when 1 mole of H2O is condensed?

c. 2 moles of H2S

The conversion of ozone to diatomic oxygen is represented by the equation above. Based on the data in the table above, what is the approximate average bond enthalpy for the oxygen-to-oxygen bonds in ozone?

c. 300kj/mol

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

A) [The diagram shows small atoms placed in the spaces between larger atoms]

(graph with mass distributions ranging from 154 to 160, highest distribution being at 158) The mass spectrum represented above is most consistent with which of the following elements?

B Gd The average atomic mass of Gd is close to 157amu. The relative abundance and masses of the isotopes shown in the mass spectrum predict an average atomic mass close to 157amu.

The two gas samples represented in the graph above are at the same temperature. Which of the following statements about the gases is correct?

C) Gas Z has a smaller molar mass than gas X.

All the chlorides of the alkaline earth metals have similar empirical formulas, as shown in the table above. Which of the following best helps explain this observation?

C. The two valence electrons of alkaline earth metal atoms are relatively easy to remove.

Which of the diagrams above best represents the CH2O molecule, and why?

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

approx temp of H2O after thermal equilibrium? (weird cup diagram)

D. 23.4 degrees C

In the reaction between C5H5N(aq) and HCl(aq) represented above, C5H5N acts as

a Brønsted-Lowry base

CaCO3 decomposes according to the balanced equation CaCO3(s)→CaO(s)+CO2(g). Based on the standard enthalpies of formation provided in the table above, what is the approximate enthalpy change of the reaction?

b. +180kj

The diagrams above represent solutes present in two different dilute aqueous solutions before they were mixed. Water molecules are not shown. When the solutions were combined, a precipitation reaction took place. Which of the diagrams below is the best particle representation of the mixture after the precipitation reaction occurred?

precipitate in the bottom, no3 and na floating

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

the one where there's a tall line at 121 and a shorter one at 123

Two sealed, rigid 5.0L containers each contain a gas at the same temperature but at a different pressure, as shown above. Also shown are the results of transferring the entire contents of container 1 to container 2. No gases escape during the transfer. Assuming ideal behavior, which statement is correct regarding the total pressure of the gases after they are combined?

A) The total pressure of the gases in the mixture is the sum of the initial pressures of oxygen gas and nitrogen gas because pressure only depends on the total amount of gas when volume and temperature are held constant.

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

A) [The diagram shows a nitrogen atom bonded to two Hydrogen atoms and an oxygen atom; the Oxygen atom is bonded to a third Hydrogen atom]

The particles in solid KI, 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?

A) [The diagram shows alternating positive and negative ions]

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?

A.

Which of the following combinations represents the individual reactions and the quantities needed to determine ΔH° for the overall reaction represented by the chemical equation above?

A.

Based on the results, what is the change in temperature reported with the correct number of significant figures?

A. 5.5 degrees C

The diagram above shows the distribution of speeds for a sample of N2(g) at 25°C. Which of the following graphs shows the distribution of speeds for a sample of O2(g) at 25°C (dashed line) ?

A. higher and longer (first diagram)

The diagram above shows two resonance structures for a molecule of C6H6. The phenomenon shown in the diagram best supports which of the following claims about the bonding in C6H6?

A. in the C6H6 molecule, all the bonds between the carbon atoms have the same length

C6H5COOH(aq)+NaOH(aq)→C6H5COONa(aq)+H2O(l) Which of the following identifies a conjugate acid-base pair in the reaction represented above?

Acid C6H5COOHC6 Conjugate base H5COO−

(graph with mass distribution highest at 90, equal at 92 and 94) 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

B 91 amu The relative abundances of the isotopes with atomic masses 90 and 92 have a weighted average that would be less than 91. That result with the influence of the mass and abundance of the isotope with atomic mass 94 would result in a weighted average closer to 91 than to 93.

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?

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

Based on the chemical equations and their associated enthalpy changes shown above, which of the following identifies the quantities needed to calculate ΔH°f the standard enthalpy of formation of H2O(l) in kJ/mol?

B.

Steel is an alloy containing Fe atoms and C atoms. Which of the following diagrams best represents the particle-level structure of steel?

B.

The table above provides the average bond enthalpies for different bond types. Based on the information in the table, which of the following mathematical expressions is correct for the estimated enthalpy change for the reaction?

B.

Which of the following Lewis diagrams best represents the bonding in the N2O molecule, considering formal charges?

B.

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

B. 1s2 2s2 2p6 3s2 3p3

Which of the following represents the electron configuration of an oxygen atom in the ground state?

C (2 arrows in 1s, 2 arrows in 2s, 2 arrows in first 2p, 1 in second and third) This configuration contains eight electrons. According to Hund's rule, each orbital in the last subshell to have electrons placed in it (in this case the 2p subshell) has one electron placed in it before pairing of electrons in orbitals occurs.

(graph with mass distribution higher at 187 and lower at 185) 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?

C 186.3amu Based on the mass spectrum, the 185amu isotope has a relative abundance close to 40% and the 187amu isotope has a relative abundance close to 60%. This predicts an average atomic mass slightly higher than 186amu.

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?

C The attractive force between the valence electrons and the nuclei of the atoms decreases. Going down the group, the net attraction of the valence electrons for the nucleus decreases; thus the valence electrons maintain a greater average distance from the nucleus.

The frequency and energy ranges of photons in some parts of the electromagnetic spectrum are given in the table above. Which of the following could be the energy of a photon in the visible range?

C) 4×10−19 J

The structures of two allotropes of carbon are represented above. Which of the following statements best helps explain why diamond is much harder than graphite?

C) Carbon atoms in diamond have four covalent bonds, whereas graphite is made of layers that are held together by relatively weak dispersion forces.

Methanol, CH3OH, dissolves completely in water to form a solution that does not conduct electricity. Which of the following diagrams best shows the major type of attractive force that exists between the particles in the solution?

C) [the diagram shows Methanol attracted to a water atom with a dashed line; the Oxygen atom from Methanol is attracted to a Hydrogen atom from water]

Based on the information for two different reactions given above, which of the following gives the quantities needed to calculate the enthalpy change for the reaction represented by the overall equation below? NO and O

C. (-delta H) + delta H

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?

C. 3,4,6,7

An equation representing the dissociation of O2(g) and a table of bond enthalpies are shown above. Based on the information, which of the following is the enthalpy of dissociation for O2(g)?

C. 495kJ/mol

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?

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

A particle-level diagram of a metallic element is shown above. Typically, metals are both malleable and ductile. The best explanation for these properties is that the electrons involved in bonding among metal atoms are

C. equally shared and form nondirectional bonds

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?

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

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

C2H5OH and H20 (both polar)

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?

C: the two main absorption bands are associated with transmission 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

The crystal structure of NaBr is represented in the diagram above. Which statement correctly compares crystalline NaBr(s) to molten NaBr(l) in terms of electrical conductivity?

D) Crystalline NaBr contains no freely moving electrons to conduct electricity, but molten NaBr is composed of freely moving Na+ and Br− ions, which allows it to be a good conductor of electricity.

The diagrams above use arrows to represent the speed of a gas particle. Which of the diagrams best represents the speed of the particles of a gas at a fixed temperature, and why?

D) Diagram 2, because the particles have a variety of different speeds.

The graph above shows how a particular real gas deviates from ideal behavior at very high pressures. Based on this information, which of the following is most likely the gas and gives the reason based on kinetic molecular theory?

D) SO2, because it has the largest molecular volume.

Which of the following complete Lewis diagrams represents a molecule containing a bond angle that is closest to 120° 120°?

D.

Based on standard enthalpies of formation, what is the approximate enthalpy for Fe2O3?

D. -820kJ/mol

The diagram above is a molecular model of a gaseous diatomic element that is just above its boiling point. Intermolecular forces between the gas molecules will cause them to condense into the liquid phase if the temperature is lowered. Which of the following best describes how the model is limited in its depiction of the phenomenon?

D. It does not show how the temporary fluctuating dipoles of the molecular electron clouds result in a net force of attraction between the molecules.

The table above summarizes data given to a student to evaluate the type of change that took place when substance X was mixed with water. The student claimed that the data did not provide enough evidence to determine whether a chemical or physical change took place and that additional tests were needed. Which of the following identifies the best way to gather evidence to support the type of change that occurred when water and X were mixed?

D. Measuring the electrical conductivities of X and the mixture of water and X

Which of the following best describes the process represented above that takes place when NH3 is added to water?

It is an acid-base reaction in which a proton is exchanged from H2O to NH3.

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?

Mg with 14 neutrons

The combustion of methane proceeds according to the chemical equation CH4+2 O2→CO2+2 H2O. The table above provides the average bond enthalpy for selected bonds. The calculated enthalpy change for the reaction, ΔHrxn, is −802 kJ/mol. Which of the following provides the mathematical procedure to estimate the bond enthalpy per mole of O2?

a. 1/2[−802 +2(799)+4(464)−4(414)]kJ/mol 2

Based on the information above, what is ΔH° for the reaction SO2(g)+12O2(g)→SO3(g)?

b. -99.1kj

The particulate-level diagram shown above best helps to explain which of the following properties of ionic solids?

B) Brittleness

Copper atoms and zinc atoms have the same atomic radius, 135 picometers. Based on this information, which of the following diagrams best represents an alloy containing only copper and zinc atoms?

B.

In an experiment to determine the specific heat of a metal, a student transferred a sample of the metal that was heated in boiling water into room-temperature water in an insulated cup. The student recorded the temperature of the water after thermal equilibrium was reached. The data are shown in the table above. Based on the data, what is the calculated heat q absorbed by the water reported with the appropriate number of significant figures?

B. 1640 J

Using a spectrophotometer, a student measures the absorbance of four solutions of CuSO4 at a given wavelength. The collected data is given in the table above. Which of the following is the most likely explanation for the discrepant data in trial 4 ?

D. The concentration of the solution was actually lower than 0.150M .

The infrared spectrum above represents the absorption of certain wavelengths of radiation by molecules of CO2. Which of the following best explains what occurs at the molecular level as the CO2 molecules absorb photons of the infrared radiation?

A) The atoms in the CO2 molecules increase their vibration as the bonds between the atoms bend and stretch.

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)?

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

When methanol and water are mixed together, they form a homogeneous mixture. Based on the information in the table above, which of the following would be the best procedure for separating a mixture of methanol and water?

B) Distillation

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

C) [The diagram shows a carbon atoms bonded to two Hydrogen atoms and two Chlorine atoms]

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?

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

Lewis diagrams of molecules of three different hydrocarbons are shown above. Which of the following claims about the molecules is best supported by the diagrams?

D. The strongest carbon-to-carbon bond occurs in molecule 3.

The graph above shows the changes in temperature recorded for the 2.00 L2.00 L of H2OH2O surrounding a constant-volume container in which a 1.00 g1.00 g sample of benzoic acid was combusted. Assume that heat was not absorbed by the container or lost to the surroundings, that the density of H2OH2O is 1.00g/mL1.00g/mL, and that the specific heat capacity of H2OH2O is about 4.2J/g⋅°C4.2J/g⋅°C. Based on this information, estimate how much heat was released from the combustion of the benzoic acid sample.

b. 25kj

C2H6(g)+7/2 O2(g)→2CO2(g)+3H2O(l) ΔH°=−1560kJ C(graphite)+O2(g)→CO2(g) ΔH°=−394kJ Given the equations and the values of ΔH° for the combustion of C2H6(g) and the combustion of C(graphite) represented above, which of the following additional information is needed to determine the values of ΔH° for the overall reaction 2C(graphite)+3H2(g)→C2H6(g) ?

c. H2(g)+1/2 O2(g)→H2O(l) ΔH°=−286kJ

particulate models of the evaporation of liquid water and the condensation of water vapor are shown above. Based on these models, which of the following accurately compares the energy changes associated with each of the phase changes?

c. The amount of energy absorbed by one mole of water molecules as they escape the liquid is equal to the amount of energy released by one mole of water molecules as they come together to form a liquid.

Natural gas consists primarily of CH4, which is combusted according to the following chemical equation. CH4(g)+2O2(g)→CO2(g)+2H2O(g) Based on the standard enthalpies of formation in the table above, which of the following expressions give the approximate enthalpy change for the reaction (ΔH°rxn

c. ΔH°rxn=[(−390kJ/mol)+2(−240kJ/mol)]−(−75kJ/mol)

Natural gas consists primarily of CH4, which is combusted according to the following chemical equation. CH4(g)+2O2(g)→CO2(g)+2H2O(g) Based on the standard enthalpies of formation in the table above, which of the following expressions give the approximate enthalpy change for the reaction (ΔH°rxn) ?

c.ΔH°rxn=[(−390kJ/mol)+2(−240kJ/mol)]−(−75kJ/mol)

The table provides data for two CH3OH samples. Based on this information, which of the following statements describes what happens when these samples are initially mixed, and why?

d. The CH3OH molecules from sample 1 transfer thermal energy to the CH3OH molecules from sample 2 through collisions because the average kinetic energy of the molecules in sample 1 is greater.

2Mg(s)+SiCl4(l)→2MgCl2(s)+Si(s) Which of the following statements about the reaction represented above is correct?

it is an oxidation-reduction reaction, and Mg is oxidized.

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.

Which of the diagrams above best represents the interactions that are responsible for the relatively large solubility of KCl crystals in water, and why?

A) Diagram 1, because strong ion-dipole interactions between KCl and water help to dissociate the solute.

(with table of properties above) 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?

B Mass percent of Na Percent by mass is an intensive property that is determined by the composition of a substance and therefore is helpful for determining the purity of the powder.

(PES graph shown above) The complete photoelectron spectrum of an element is given above. Which labeled peak corresponds to the 1s electrons and why?

B Peak X, because 1s electrons have the strongest attractions to the nucleus. Greater binding energies correlate to stronger attractions to the nucleus.

(PES graph shown above) 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?

B The spectrum shows a single electron in the 2p subshell. The spectrum is consistent with the electron configuration for boron: 1s22s22p1. The leftmost peak represents the two electrons in the filled 1s subshell. The two peaks on the right represent the two electrons in the filled 2s subshell and the single electron in the 2p subshell.

Based on the information in the table above, which of the following expressions gives the approximate ΔH for the reaction represented by the following balanced chemical equation?

B.

Shown above are the equation representing the decomposition of H2O2(l) and a table of bond enthalpies. On the basis of the information, which of the following is the enthalpy of decomposition of 2 mol of H2O2(l)?

B. -203kJ

The diagram above shows a thin-layer chromatogram of a mixture of products from a chemical reaction. The separation was performed using 50% ethyl acetate in hexane as the solvent (mobile phase) and silica gel as the polar stationary phase. On the basis of the chromatogram and the information about solvents in the table above, which of the following would be the best way to decrease the distance that the products travel up the plate?

B. Decrease the percentage of ethyl acetate in the solvent.

A student places a piece of I2(s) in 50.0 mL of H2O(l), another piece of I2(s) of the same mass in 50.0 mL of C6H14(l), and shakes the mixtures. The results are shown above. What do the results indicate about the intermolecular interactions of the substances?

B. I2 and C6H14 have similar intermolecular interactions, and I2 and H2O do not

A solid compound of a group 1 (alkali) metal and a group 17 (halogen) element dissolves in water. The diagram above represents one type of solute particle present in the solution. Which of the following identifies the solute particle and best helps explain how the solute particle interacts with water molecules?

C) The particle is a positive ion, and the interactions are ion-dipole attractions.

The diagrams above represent two samples of Xe gas in containers of equal volume at 280K. Which of the following correctly compares the two samples in terms of their deviation from ideal gas behavior and explains why?

B. The gas in sample 2 would deviate more from ideal behavior because the Xe atoms are closer together, leading to an increase in intermolecular attractions.

A student places a sample of a pure metal in a crucible and heats it strongly in air. Data from the experiment are given in the table above. The final mass was determined after the sample was cooled to room temperature. Which of the following statements related to the experiment is correct?

B. The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance.

The diagram above shows the distribution of speeds for a sample of O2(g). Which of the following graphs shows the distribution of speeds for the same sample at a higher temperature (dashed line) ?

C) [graph with dashed line's peak at center and below original line]

In the following diagrams, elements are represented by X and Z which form molecular compounds with one another. Which diagram represents a molecule that has a bent molecular geometry?

B. Z:X:Z w/ 2 lone pairs on X

(two diagrams shown above) Which particle diagram shown above best represents the strongest intermolecular force between two ethanol, C2H6O, molecules?

C) Diagram 2, because it shows the formation of a hydrogen bond between an H atom bonded to an O atom with an O atom from another molecule.

The diagram above shows thin-layer chromatograms of the same mixture of two compounds. Based on the chromatograms, which solvent would be most effective at separating the two compounds if the same stationary phase is used for column chromatography?

C) Solvent C

Four different liquid compounds in flasks at 20°C are represented above. The table below identifies the compounds. Flask C shows the most particles in the vapor phase. Which of the following is not shown in the model but best helps to explain why flask C must contain pentane?

C. The strength of the intermolecular forces btwn the particles in the liquid

The graph above shows the distribution of molecular speeds for four different gases at the same temperature. What property of the different gases can be correctly ranked using information from the graph, and why?

D. The molecular masses of the gases, because the gas molecules have the same average kinetic energy and mass can be calculated using the equation KEavg=12mv2 .

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?

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

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?

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

The heating curve for 1.0 mole of Na, initially at 25.0°C, is shown above at the left. Which of the following best explains the change in heat when 0.50 mole of Na Na undergoes the transition shown in the diagram above to the right?

b. Approximately 49kJ of heat are absorbed to overcome the attractive forces acting between Na atoms.

The table above provides the values for the standard enthalpy change for two chemical reactions. A student needs to calculate the enthalpy change for the reaction 2HNO3(l)→N2O5(g)+H2O(l) under standard conditions using Hess's law. In addition to the values given in the table, what other information will the student need to perform the calculation?

b. ΔHof for N2O5(g)

The formation of hydrogen chloride gas is represented by the chemical equation H2(g)+Cl2(g)→2HCl(g). Based on the bond enthalpy data in the table above, what is the approximate enthalpy change for the reaction?

b. −185kJ/molrxn

A student dissolves 8.00 g of NH4NO3(s) in 100. g of H2O(l) in a coffee-cup calorimeter. Based on the initial and final temperatures of the mixture in degrees Celsius shown in the diagram above the laboratory setup, what is the calculated ΔT of the water reported to the appropriate number of significant figures

c. -5.5 C