AP Chemistry S1 Final

Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains exactly two unpaired electrons (A) S (B) Ca (C) Ga (D) Sb (E) Br

(A) S

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 B (1.85)(35.0)/(0.0821)(3.00) atm C 3.00/(1.85)(0.0821)(308) atm D (1.85)(8.314)(308)/3.00 atm E 3.00(1.85)/(0.0821)(35.0) atm

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

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

A 0

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 B 2[−802+799+2(464)−2(414)]kJ/mol C 1/2[−802−2(360)+4(464)+4(414)]kJ/mol D 2[−802−(360)+2(464)+4(414)]kJ/mol

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

A student mixes 50mL of 1.0M HCl and 50mL of 1.0M NaOH in a coffee-cup calorimeter and observes the change in temperature until the mixture reaches thermal equilibrium. The initial and final temperatures (°C) of the mixture are shown in the diagram above of the laboratory setup. Based on the results, what is the change in temperature reported with the correct number of significant figures? A 5.5°C B 5.50°C C 5.500°C D 6°C

A 5.5°C

On the basis of the data provided above, the gas in container 3 could be A CH4 B O2 C Ar D CO2

A CH4

Based on the Brønsted-Lowry theory of acids and bases, which of the following species can act as both a conjugate acid and a conjugate base? A HS− B CH3COO− C H3O+ D Nh4+

A HS−

A 0.5 mol sample of He(g) and a 0.5 mol sample of Ne(g) are placed separately in two 10.0 L rigid containers at 25°C. Each container has a pinhole opening. Which of the gases, He(g) or Ne(g), will escape faster through the pinhole and why? A He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms. B Ne(g) will escape faster because its initial pressure in the container is higher. C Ne(g) will escape faster because the Ne(g) atoms have a higher average kinetic energy than the He(g) atoms. D Both gases will escape at the same rate because the atoms of both gases have the same average kinetic energy.

A He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms.

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. B Because of variable bonding between its carbon atoms, C6H6 is a good conductor of electricity. C The bonds between carbon atoms in C6H6 are unstable, and the compound decomposes quickly. D The C6H6 molecule contains three single bonds between carbon atoms and three double bonds between carbon atoms.

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

Which of the following statements about the reaction represented above is correct? A It is an oxidation-reduction reaction, and Mg is oxidized. B It is an oxidation-reduction reaction, and electrons are transferred from SiCl4 to Mg C It is an oxidation-reduction reaction, and the oxidation number of Cl changes from +4 to +2. D It is not an oxidation-reduction reaction because none of the oxidation numbers change.

A It is an oxidation-reduction reaction, and Mg is oxidized.

Which of the following best helps explain why the pressure of a sample of CH4(g) (molar mass 16g/mol) is closer to the pressure predicted by the ideal gas law than a sample of NH3(g) (molar mass 17g/mol) ? A NH3 molecules are polar while CH4 molecules are not, and the greater attractions between NH3 molecules cause the molecules to collide with the walls of the container with less force. B NH3 molecules have a greater molar mass than CH4 molecules, so the NH3 molecules collide with the walls of the container with more force. C CH4 molecules have more hydrogen atoms than NH3 molecules, so CH4 molecules have more hydrogen bonding and greater intermolecular forces. D CH4 molecules are larger than NH3 molecules, so the actual CH4 molecules take up a significant portion of the volume of the gas.

A NH3 molecules are polar while CH4 molecules are not, and the greater attractions between NH3 molecules cause the molecules to collide with the walls of the container with less force.

Which of the following statements, if true, would support the claim that the NO3− ion, represented above, has three resonance structures? A The NO3− ion is not a polar species. B The oxygen-to-nitrogen-to-oxygen bond angles are 90°. C One of the bonds in NO3− is longer than the other two. D One of the bonds in NO3− is shorter than the other two.

A The NO3− ion is not a polar species.

A student has samples of two pure compounds, XClO3 and ZClO3, which contain unknown alkali metals X and Z. The student measures the mass of each sample and then strongly heats the samples to drive off all the oxygen, leaving solid residues of XCl and ZCl. The student measures the mass of the solid residue from each sample. Which of the following questions can be answered from the results of the experiment? A Which has the greater molar mass, X or Z? B Which has the higher boiling point, X or Z? C Which has the higher melting point, XCl or ZCl? D Which has the greater density, XCl or ZCl?

A Which has the greater molar mass, X or Z?

In the reaction between C5H5N(aq) and HCl(aq) represented above, C5H5N acts as A a Brønsted-Lowry base B a Brønsted-Lowry acid C the conjugate base of HCl D the conjugate acid of

A a Brønsted-Lowry base

At standard temperature and pressure, a 0.50 mol sample of H2 gas and a separate 1.0 mol sample of O2 gas have the same A average molecular kinetic energy B average molecular speed C volume D effusion rate E density

A average molecular kinetic energy

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.) A ns2 B ns2np1 C ns2np2 D ns2np3

A ns2

At 27°C, five identical rigid 2.0 L vessels are filled with N2(g) and sealed. Four of the five vessels also contain a 0.050 mol sample of NaHCO3(s), NaBr(s), Cu(s), or I2(s), as shown in the diagram above. The volume taken up by the solids is negligible, and the initial pressure of N2(g) in each vessel is 720 mm Hg. All four vessels are heated to 127°C and allowed to reach a constant pressure. 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 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)

A solution is prepared by adding 16 g of CH3OH (molar mass 32 g) to 90.0 g of H2O (molar mass 18 g). The mole fraction of CH3OH in this solution is closest to which of the following? A) 0.1 B) 0.2 C) 0.3 D) 0.4 E) 0.6

A) 0.1

How many carbon atoms are contained in 2.8 g of C2H4 ? A) 1.2 x 10^23 B) 3.0 x 10^23 C) 6.0 x 10^23 D) 1.2 x 10^24 E) 6.0 x 10^24

A) 1.2 x 10^23

How many protons, neutrons, and electrons are in an 56/26 Fe atom? A) 26 protons, 30 neutrons, 26 electrons B) 26 protons, 56 neutrons, 26 electrons C) 30 protons, 26 neutrons, 30 electrons D) 56 protons, 26 neutrons, 26 electrons E) 56 protons, 82 neutrons, 56 electrons

A) 26 protons, 30 neutrons, 26 electrons

Which of the following lists Mg, P, and Cl in order of increasing atomic radius? A) Cl < P < Mg B) Cl < Mg < P C) Mg < P < Cl D) Mg < Cl < P E) P < Cl < Mg

A) Cl < P < Mg

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? A) Na B) H+ C) K+ D) Cl−

A) Na

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 placed with those of a different element? A) P atoms introduce additional mobile negative charges B) P atoms introduce additional mobile positive charges C) Ge atoms have more electrons than Si atoms have D) Ge atoms are much smaller than Si atoms

A) P atoms introduce additional mobile negative charges

CaCO3 decomposes according to the balanced equation CaCO3(s)→CaO(s)+CO2(s). Based on the standard enthalpies of formation provided in the table above, what is the approximate enthalpy change of the reaction? A −180kJ B +180kJ C −1460kJ D +1460kJ

B +180kJ

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 absorbed by the water reported with the appropriate number of significant figures? A 1600J B 1640J C 1642J D 1700J

B 1640J

The complete photoelectron spectrum of an element is given above. Which of the following electron configurations is consistent with the spectrum? A 1s2 2s2 2p1 B 1s2 2s2 2p6 3s2 3p3 C 1s2 2s2 2p6 3s2 3p6 D 1s2 2s2 2p6 3s2 3p6 4s2 3d5

B 1s2 2s2 2p6 3s2 3p3

When 6.0 L of He(g) and 10. L of N2(g), both at 0oC and 1.0 atm, are pumped into an evacuated 4.0 L rigid container, the final pressure in the container at 0oC is A 2.0 atm B 4.0 atm C 6.4 atm D 8.8 atm E 16 atm

B 4.0 atm

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? A 3.0 atm B 4.5 atm C 9.0 atm D 18 atm

B 4.5 atm

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

B 5.0g/56g/mol

2CO(g)+C(g)→C3O2(g)ΔH°=127.3kJ/molrxn The equation shown above represents an endothermic reaction between CO(g) and C(g). What is the amount of heat absorbed when 1.00mol of CO(g) reacts with an excess of C(g) ? A 31.8kJ B 63.7kJ C 127.3kJ D 254.6kJ

B 63.7kJ

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 90amu B 91⁢⁢amu C 93amu D 94 amu

B 91⁢⁢amu

C6H5COOH(aq)+NaOH(aq)→C6H5COONa(aq)+H2O(l) Which of the following identifies a conjugate acid-base pair in the reaction represented above? A Acid C6H5COOH Conjugate base OH− B Acid C6H5COOH Conjugate base C6H5COO− C Acid OH− Conjugate base H2O D Acid OH− Conjugate base C6H5COO−

B Acid C6H5COOH Conjugate base C6H5COO−

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 undergoes the transition shown in the diagram above to the right? A Approximately 13kJ of heat are absorbed as a result of the increase in potential energy between the Na atoms. B Approximately 49kJ of heat are absorbed to overcome the attractive forces acting between Na atoms. C Approximately 98kJ of heat are released as a result of the decrease in the kinetic energy of the Na atoms. D Approximately 120kJ of heat are released to decrease the potential energy between Na atoms.

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

Which flask contains the smallest number of moles of gas? A A B B C C D D E E

B B

A student carefully drops a 9.0g solid Zn pellet initially at 50.0°C into an insulated cup containing 30.0g of water at 27.8°C. The student predicts that the temperature of the water will increase after the pellet is added. Which of the following statements is the best justification for the student's prediction? A The metallic bonds between Zn atoms will break when the Zn is exposed to the water molecules, B Collisions between the water molecules and the surface of the Zn pellet will result in the transfer of energy, increasing the average kinetic energy of the water molecules. C The strength of the hydrogen bonds between the water molecules will increase when the Zn pellet is added, decreasing the average kinetic energy of the water molecules. D Collisions between Zn atoms in the solid will increase in frequency when the Zn is exposed to the water molecules, resulting in the transfer of energy to the surroundin

B Collisions between the water molecules and the surface of the Zn pellet will result in the transfer of energy, increasing the average kinetic energy of the water molecules.

5Fe2+(aq)+MnO4−(aq)+8H+(aq)→5Fe3+(aq)+Mn2+(aq)+4H2O(l) Which of the following represents the oxidation half-reaction based on the balanced ionic equation shown above? A Fe2+(aq)+e-−→Fe3+(aq) B Fe2+(aq)→Fe3+(aq)+e− C MnO4−(aq)→Mn2+(aq)+5e− D MnO4-(aq)+5e-→Mn2+(aq)

B Fe2+(aq)→Fe3+(aq)+e−

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

B Gd

CO(g) + 2 H2(g) ⇄ CH3OH(g) ΔH < 0 The synthesis of CH3OH(g) from CO(g) and H2(g) is represented by the equation above. The value of Kc for the reaction at 483 K is 14.5. A mixture of CO(g) and H2(g) is pumped into a previously evacuated 2.0 L reaction vessel. The total pressure of the reaction system is 1.2 atm at equilibrium. What will be the total equilibrium pressure of the system if the volume of the reaction vessel is reduced to 1.0 L at constant temperature? A Less than 1.2 atm B Greater than 1.2 atm but less than 2.4 atm C 2.4 atm D Greater than 2.4 atm

B Greater than 1.2 atm but less than 2.4 atm

Which of the following elements has the mass spectrum represented above? A Nb B Mo C U D

B Mo

The elements C and Se have the same electronegativity value, 2.55. Which of the following claims about the compound that forms from C and Se is most likely to be true? A The carbon-to-selenium bond is unstable. B The carbon-to-selenium bond is nonpolar covalent. C The compound has the empirical formula CSe. D A molecule of the compound will have a partial negative charge on the carbon atom.

B The carbon-to-selenium bond 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

When a sample of oxygen gas in a closed container of constant volume is heated until its absolute temperature is doubled, which of the following is also doubled? A The density of the gas B The pressure of the gas C The average velocity of the gas molecules D The number of molecules per cm3 E The potential energy of the molecules

B The pressure of the gas

The reaction between NO(g) and O2(g) to produce NO2(g) in a rigid reaction vessel is represented in the diagram above. The pressure inside the container is recorded using a pressure gauge. Which of the following statements correctly predicts the change in pressure as the reaction goes to completion at constant temperature, and provides the correct explanation? A The pressure will increase because the product molecules have a greater mass than either of the reactant molecules. B The pressure will decrease because there are fewer molecules of product than of reactants. C The pressure will decrease because the product molecules have a lower average speed than the reactant molecules. D The pressure will not change because the total mass of the product molecules is the same as the total mass of the reactant molecules.

B The pressure will decrease because there are fewer molecules of product than of reactants.

Of the following, the best explanation for the fact that most gases are easily compressed is that the molecules in a gas A are in constant motion B are relatively far apart C have relatively small masses D have a real, nonzero volume E move slower as temperature decreases

B are relatively far apart

Refer to three gases in identical rigid containers under the conditions given in the table below. The density of the gas, in g/L, is A greatest in container A B greatest in container B C greatest in container C D the same in all three containers

B greatest in container B

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? A ΔH∘ for N2(l) B ΔH∘ for N2O5(g) C ΔH∘ for H2O(g) D ΔH∘ for H2(l)

B ΔH∘ 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? A −247kJ/molrxn B −185kJ/molrxn C +185kJ/molrxn D +247kJ/molrxn

B −185kJ/molrxn

Based on the information above, what is ΔH° for the reaction SO2(g)+12O2(g)→SO3(g) ? A −591.3kJ/molrxn B −99.1kJ/molrxn C +99.1kJ/molrxn D +591.3kJ/molrxn

B −99.1kJ/molrxn

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)

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

B)

Of the following electron configurations of neutral atoms, which represents an atom in an excited state? A) 1s2 2s2 2p5 B) 1s2 2s2 2p5 3s2 C) 1s2 2s2 2p6 3s1 D) 1s2 2s2 2p6 3s2 3p2 E) 1s2 2s2 2p6 3s2 3p5

B) 1s2 2s2 2p5 3s2

The complete photoelectron spectrum of an element is given above. Which of the following electron configurations is consistent with the spectrum? A) 1s2 2s2 2p1 B) 1s2 2s2 2p6 3s2 3p3 C) 1s2 2s2 2p6 3s2 3p6 D) 1s2 2s2 2p6 3s2 3p6 4s2 3d5

B) 1s2 2s2 2p6 3s2 3p3

Based on periodic trends and the data in the table above, which of the following are the most probable values of the atomic radium and the first ionization energy for potassium repsectively? A) 242 pm, 633 kj/mol B) 242 pm, 419 kj/mol C) 120 pm, 633 kj/mol D) 120 pm, 419 kj/mol

B) 242 pm, 419 kj/mol

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

B) 55 Protons, 79 neutrons, 55 electrons

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? A) B, because it has five core electrons B) B, because it has three valence electrons C) N, because it has five valence electrons D) N, because it has three electrons in the p sublevel

B) B, because it has three valence electrons

In which of the following compounds is the mass ratio of chromium to oxygen closest to 1.6 to 1.0? A) CrO3 B) CrO2 C) CrO D) Cr2O E) Cr2O3

B) CrO2

Which of the following best helps with the fact that F- ion is smaller than the O2- ion? A) F- has a larger nuclear mass than O2- has B) F- has a larger nuclear charge than O2- has C) F- has more electrons than O2- has D) F- is more electronegative than O2- is E) F- is more polarizable than O2- is

B) F- has a larger nuclear charge than O2- has

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? A) Al with 13 neutrons B) Mg with 14 neutrons C) Fe with 26 neutrons D) Ti with 26 neutrons

B) Mg with 14 neutrons

Which of the following elements has the mass spectrum represented above? A) Nb B) Mo C) U D) Cf

B) Mo

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? A) Na has a greater density at standard conditions than Ne B) Na has a lower first ionization energy than Ne C) Na has a higher melting point than Ne D) Na has a higher neutron-to-proton ratio than Ne E) Na has fewer naturally occuring isotopes than Ne

B) Na has a lower first ionization energy than Ne

Forms monatomic ions with 2- charge in solutions A) F B) S C) Mg D) Ar E) Mn

B) S

After completing an experiment to determine gravimetrically the percentage of water in a hydrate, a student reported a value of 38 percent. The correct value for the percentage of water in the hydrate is 51 percent. Which of the following is the most likely explanation for this difference? A)Strong initial heating caused some of the hydrate sample to spatter out of the crucible. B)The dehydrated sample absorbed moisture after heating. C)The amount of the hydrate sample used was too small. D)The crucible was not heated to constant mass before use. E)Excess heating caused the dehydrated sample to decompose.

B) The dehydrated sample absorbed moisture after heating.

A student is given two 10g samples, each a mixture of only NaCl(s) and KCl(s) but in different proportions. Which of the following pieces of information could be used to determine which mixture has the higher proportion of KCl(s) ? A) The volume of each mixture B) The mass of Cl in each mixture C) The number of isotopes of Na and K D) The reaction of each mixture with water

B) The mass of Cl in each mixture

A student is given two 10g samples, each a mixture of only NaCl(s) and KCl(s) but in different proportions. Which of the following pieces of information could be used to determine which mixture has the higher proportion of KCl(s) ? A. The volume of each mixture B. The mass of Cl in each mixture C. The number of isotopes of Na and K D. The reaction of each mixture with water

B. The mass of Cl in each mixture

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 186.0amu C 186.3amu D 186.9 amu

C 186.3amu

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? A 0.5 mole of H2S B 1 mole of H2S C 2 moles of H2S D 4 moles of

C 2 moles of H2S

Reaction 1: 2O3(g)→3O2(g) Reaction 2:? Overall reaction: 2O3(g)+2NO(g)→2NO2(g)+2O2(g) The enthalpy of the overall reaction represented above can be determined by adding the enthalpies of reactions 1 and 2. Which of the following could be reaction 2 ? A NO(g)+O(g)→NO2(g) B (NO)2(g)→2NO(g) C 2NO(g)+O2(g)→2NO2(g) D 2NO(2g)+O3(g)→N2O5(g)+O2(g)

C 2NO(g)+O2(g)→2NO2(g)

A 2 L sample of N2(g) and a 1 L sample of Ar(g), each originally at 1 atm and 0°C, are combined in a 1 L tank. If the temperature is held constant, what is the total pressure of the gases in the tank? A 1 atm B 2 atm C 3 atm D 4 atm E 5 atm

C 3 atm

2O3(g)→3O2(g) ΔHrxn∘=−300kJ/molrxn 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? A 0kJ/mol B 150kJ/mol C 300kJ/mol D 500kJ/mol

C 300kJ/mol

Na2S2O3(aq)+4NaOCl(aq)+2NaOH(aq)→2Na2SO4(aq)+4NaCl(aq)+H2O(l) The enthalpy change for the reaction represented by the chemical equation shown above is ΔH°=−1236kJ/molrxn. When 2.00mol of NaOCl(aq) reacts completely with an excess of Na2S2O3(aq) and of NaOH(aq), which of the following enthalpy changes occurs? A 618kJ of heat is absorbed. B 2470kJ of heat is absorbed. C 618kJ of heat is released. D 2470kJ of heat is released.

C 618kJ of heat is released.

A gas mixture at 0°C and 1.0atm contains 0.010mol of H2, 0.015mol of O2, and 0.025mol of N2. Assuming ideal behavior, what is the partial pressure of hydrogen gas (H2) in the mixture? A About 0.010atm, because there is 0.010mol of H2 in the sample. B About 0.050atm, because there is 0.050mol of gases at 0°C and 1.0atm. C About 0.20atm, because H2 comprises 20% of the total number of moles of gas. D About 0.40atm, because the mole ratio of H2:O2:N2 is 0.4:0.6:1.

C About 0.20atm, because H2 comprises 20% of the total number of moles of gas.

A gas mixture at 0°C and 1.0atm contains 0.010mol of H2, 0.015mol of O2, and 0.025mol of N2. Assuming ideal behavior, what is the partial pressure of hydrogen gas (H2) in the mixture? A About 0.010atm, because there is 0.010mol of H2 in the sample. B About 0.050atm, because there is 0.050mol of gases at 0°C and 1.0atm. C About 0.20atm, because H2 comprises 20% of the total number of moles of gas. D About 0.40atm, because the mole ratio of H2:O2:N2 is 0.4:0.6:1.

C About 0.20atm, because H2 comprises 20% of the total number of moles of gas.

The following questions refer to the 1 L flasks shown below. Which flask contains the sample with the greatest density? A A B B C C D D E E

C C

C2H6(g)+7/2O2(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) ? A C(diamond)→C(graphite) ΔH°=−2kJ B C2H4(g)+H2(g)→C2H6(g) ΔH°=−134kJ C H2(g)+12O2(g)→H2O(l)⁢ ΔH°=−286kJ D H2O(l)→H2O(g) ΔH°=+41kJ

C H2(g)+12O2(g)→H2O(l)⁢ ΔH°=−286kJ

sample of an ideal gas is cooled from 50.0oC to 25.0oC in a sealed container of constant volume. Which of the following values for the gas will decrease? I. The average molecular mass of the gas II. The average distance between the molecules III. The average speed of the molecules A I only B II only C III only D I and III E II and III

C III only

Two pure elements react to form a compound. One element is an alkali metal, X, and the other element is a halogen, Z. Which of the following is the most valid scientific claim that can be made about the compound? A It has the formula XZ2. B It does not dissolve in water. C It contains ionic bonds. D It contains covalent bonds.

C It contains ionic bonds.

Equal masses of three different ideal gases, X, Y, and Z, are mixed in a sealed rigid container. If the temperature of the system remains constant, which of the following statements about the partial pressure of gas X is correct? A It is equal to ⅓ the total pressure B It depends on the intermolecular forces of attraction between molecules of X, Y, and Z. C It depends on the relative molecular masses of X, Y, and Z. D It depends on the average distance traveled between molecular collisions. E It can be calculated with knowledge only of the volume of the container.

C It depends on the relative molecular masses of X, Y, and Z.

Which of the following correctly indicates whether the solid represented by the particulate model shown above conducts electricity and explains why or why not? A It conducts electricity because it is made of positive and negative ions. B It conducts electricity because it is made of particles of different sizes. C It does not conduct electricity because its ions cannot move freely within the solid. D It does not conduct electricity because there are small spaces between the particles.

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

HCl(aq)+NH3(aq)→NH4+(aq)+Cl−(aq) The chemical reaction between HCl(aq) and NH3(aq) is represented above. A student combines equimolar amounts of HCl(aq) and NH3(aq), both solutions initially at 24°C, in a coffee-cup calorimeter. The student observes that the mixture reaches a temperature of 28°C. Based on the experimental results, which of the following can be concluded about the reaction? A It is an endothermic process, because energy is released by the reaction and is gained by the reaction mixture. B It is an endothermic process, because energy is absorbed by the reaction and is lost from the reaction mixture. C It is an exothermic process, because energy is released by the reaction and is gained by the reaction mixture. D It is an exothermic process, because energy is absorbed by the reaction and is lost from the reaction mixture.

C It is an exothermic process, because energy is released by the reaction and is gained by the reaction mixture.

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? A Mass of the sample, volume of the sample B Mass of the sample, density of the sample C Molar mass of the compound, mass of the sample D Molar mass of the compound, density of the sample

C Molar mass of the compound, mass of the sample

Based on these models, compares the energy changes associated with each of the phase changes? A The amount of energy absorbed by one mole of water molecules as they escape the liquid is greater than the amount of energy released by one mole of water molecules as they come together to form a liquid. B The amount of energy absorbed by one mole of water molecules as they escape the liquid is less than the amount of energy released by one mole of water molecules as they come together to form a liquid. 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. D The amount of energy absorbed by one mole of water molecules escaping the liquid can be either greater than or less than the amount of energy released by one mole of water molecules as they come together to form a liquid.

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.

Element: N P As Sb Bi Atomic Radius 65 100 115 145 160 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.

A rigid metal tank contains oxygen gas. Which of the following applies to the gas in the tank when additional oxygen is added at constant temperature? A The volume of the gas increases. B The pressure of the gas decreases. C The average speed of the gas molecules remains the same. D The total number of gas molecules remains the same. E The average distance between the gas molecules increases.

C The average speed of the gas molecules remains the same.

A student combines a solution of NaCl(aq) with a solution of AgNO3(aq), and a precipitate forms. Which of the following is evidence that ionic bonds formed during the precipitation? A The resulting solution is colorless. B The resulting solution conducts electricity. C The precipitate has a high melting point. D The temperature of the solution did not change significantly during the precipitation.

C The precipitate has a high melting point.

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? A The random motion of the particles within the liquids B The relative speeds of the vapor particles in each flask C The strength of the intermolecular forces between the particles in the liquids D The structural formula of the molecules of the liquid and vapor in each flask

C The strength of the intermolecular forces between the particles in the liquids

Metal: Be Mg Ca Sr Ba Ra Formula of Metal Chloride: BeCl2 MgCl2 CaCl2 SrCl2 BaCl2 RaCl2 All the chlorides of the alkaline earth metals have similar empirical formulas, as shown in the table above. Which of the following best helps to explain this observation? A Cl2(g) reacts with metal atoms to form strong, covalent double bonds. B Cl has a much greater electronegativity than any of the alkaline earth metals. C The two valence electrons of alkaline earth metal atoms are relatively easy to remove. D The radii of atoms of alkaline earth metals increase moving down the group from Be to Ra.

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

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.

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 A unequally shared and form nondirectional bonds B unequally shared and form highly directional bonds C equally shared and form nondirectional bonds D equally shared and form highly directional bonds

C equally shared and form nondirectional bonds

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 (ΔHrxn°) ? A ΔHrxn°=(−75kJ/mol)−[(−390kJ/mol)+2(−240kJ/mol)] B ΔHrxn°=(−75kJ/mol)−[(−390kJ/mol)+(−240kJ/mol)] C ΔHrxn°=[(−390kJ/mol)+2(−240kJ/mol)]−(−75kJ/mol) D ΔHrxn°=[(−390kJ/mol)+(−240kJ/mol)]−(−75kJ/mol)

C ΔHrxn°=[(−390kJ/mol)+2(−240kJ/mol)]−(−75kJ/mol)

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? A −5.500°C B −5.50°C C −5.5°C D -6°C

C −5.5°C

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

C)

Which of the following is the ground-state electron configuration of the F− ion? A) 1s2 2s2 2p4 B) 1s2 2s2 2p5 C) 1s2 2s2 2p6 D) 1s2 2s2 2p6 3s2 3p6

C) 1s2 2s2 2p6

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 A) Na B) Mg C) Al D) Si E) P

C) Al

The atom that contains only one electron in the highest occupied energy sublevel A) S B) Ca C) Ga D) Sb E) Br

C) Ga

When hafnium metal is heated in an atmosphere of chlorine gas, the product of the reaction is found to contain 62.2 percent Hf by mass and 37.4 percent Cl by mass. What is the empirical formula for this compound? A) HfCl B) HfCl2 C) HfCl3 D) HfCl4 E) Hf2Cl3

C) HfCl3

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? A) A neutral atom of the element contains exactly two electrons B) The element does not react with other elements to form compounds C) In its compounds, the element tends to form ions with a charge of +1 D) In its compounds, the element tends to form ions with a charge of +3

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

A compound contains 1.10mol of K, 0.55mol of Te, & 1.65mol of O. What is the simplest formula of this compound A) KTeO B) KTe2O C) K2TeO3 D) K2TeO6 E) K4TeO6

C) K2TeO3

A compound contains 30% sulfur and 70% fluorine by mass. The empirical formula of the compound is A) SF B) SF2 C) SF4 D) SF6 E) S2F

C) SF4

Diagram 1 above shows equimolar samples of two gases inside a container fitted with a removable barrier placed so that each gas occupies the same volume. The barrier is carefully removed as the temperature is held constant. Diagram 2 above shows the gases soon after the barrier is removed. Which statement describes the changes to the initial pressure of each gas and the final partial pressure of each gas in the mixture and also indicates the final total pressure?

C) The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is half the sum of the initial pressures of the two gases.

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? 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

Which of the following best helps explain why the electronegativity of Cl is less than that of F? A) The mass of the Cl atom is greater than the mass of the F atom B) The Cl nucleus contains more protons than the F nucleus contains C) When Cl and F form bonds with other atoms, the Cl bonding electrons are more shielded from the positive Cl nucleus than the F bonding electrons are shielded from the positive F nucleus. D) Because Cl is larger than F, the repulsions among electrons in the valence shell of Cl are less than the repulsions among electrons in the valence shell of F

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

For element X represented above, which of the following is most likely explanation for the large difference between the second and third ionization energies? A) the effective nuclear charge decreases with successive ionizations B) the shielding of outer electrons increases with successive ionizaitons C) the electron removed during the third ionization is, on average, much closer to the nucleus that the first two electrons removed were D) the ionic radius increases with successive ionization

C) the electron removed during the third ionization is, on average, much closer to the nucleus that the first two electrons removed were

Which of the following best represents the ground-state electron configuration for an atom of selenium? A. 1s² 2s² 2p⁶ 3s²3 p³ B. 1s² 2s² 2p⁶ 3s² 3p⁴ C. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴ D. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵

C. 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴

Which of the following numerical expressions gives the number of particles in 2.0g of Ne? A. 6.0x10²³ particles/mol/ 2.0g B. 6.0x10²³ particles/mol/ 20.18 g/mol C. 2.0g/ 20.18 g/mol x (6.0x10²³ particles/mol) D. 20.18 g/mol/ 2.0g x (6.0x10²³ particles/mol)

C. 2.0g/ 20.18 g/mol x (6.0x10²³ particles/mol)

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? A. Mass of the sample, volume of the sample B. Mass of the sample, density of the sample C. Molar mass of the compound, mass of the sample D. Molar mass of the compound, density of the sample

C. Molar mass of the compound, mass of the sample

For an experiment, a 20.0 g piece of Al was placed inside an insulated cup filled with 40.0 g of H2O. The data are given in the table above. Assuming no heat is absorbed by the container or the surroundings, which of the following equations provides the correct mathematical relationship for the transfer of heat q between Al and H2O? A −qAl=10×qH2O B −qAl=5×qH2O C −qAl=2×qH2O D -qAl=qH2O

D -qAl=qH2O

2Al(s)+Fe2O3(s)→2Fe(s)+Al2O3(s)ΔH°=−850kJ/molrxn The chemical equation shown above represents the thermite reaction. What is the approximate amount of heat released when 108g of Al(s) reacts with excess Fe2O3(s) ? A 210kJ B 430kJ C 850kJ D 1700kJ

D 1700kJ

A sealed vessel contains 0.200 mol of oxygen gas, 0.100 mol of nitrogen gas, and 0.200 mol of argon gas. The total pressure of the gas mixture is 5.00 atm. The partial pressure of the argon is A 0.200 atm B 0.500 atm C 1.00 atm D 2.00 atm E 5.00 atm

D 2.00 atm

RbCl has a high boiling point. Which of the following compounds is also likely to have a high boiling point, and why? A NO, because its elements are in the same period of the periodic table. B ClF, because its elements are in the same group of the periodic table. C Cl2O, because its elements have similar electronegativities and it is a covalent compound. D CsCl, because its elements have very different electronegativities and it is an ionic compound.

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

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? A It does not show how hydrogen bonds are constantly forming, breaking, and reforming, which results in a net force of attraction between the molecules. B It does not show how the interactions between ions and the induced molecular dipoles result in a net force of attraction between the molecules. C It does not show how the interacting permanent dipoles of the molecules result in a net force of attraction between the molecules. 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.

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 electron cloud of HF is smaller than that of F2 , however, HF has a much higher boiling point than F2 has. Which of the following explains how the dispersion-force model of intermolecular attraction does not account for the unusually high boiling point of HF? A F2 is soluble in water, whereas HF is insoluble in water. B The F2 molecule has a greater mass than the HF molecule has. C Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HF has strong ionic interactions between H+ and F− ions. D Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.

D Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.

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 phase changes involves the transfer of heat from the surroundings to the system? A CH4(g)→CH4(l), because CH4 molecules in the gas phase must absorb energy in order to move closer together, thereby increasing the intermolecular attractions in the solid state. B CO2(g)→CO2(l), because CO2 molecules in the gas phase must absorb energy in order to move closer together, thereby increasing the intermolecular attractions in the liquid state. C H2O(l)→H2O(s), because H2O molecules in the liquid phase must absorb energy in order to create a crystalline structure with strong intermolecular attractions in the solid state. D NH3(l)→NH3(g), because NH3 molecules in the liquid phase must absorb energy in order to overcome their intermolecular attractions and become free gas molecules.

D NH3(l)→NH3(g), because NH3 molecules in the liquid phase must absorb energy in order to overcome their intermolecular attractions and become free gas molecules.

A 1L sample of helium gas at 25°C and 1atm is combined with a 1L sample of neon gas at 25°C and 1atm. The temperature is kept constant. Which of the following statements about combining the gases is correct? A The average speed of the helium atoms increases when the gases are combined. B The average speed of the neon atoms increases when the gases are combined. C The average kinetic energy of the helium atoms increases when the gases are combined. D The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.

D The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.

Which of the following scientific claims about the bond in the molecular compound HF is most likely to be true? A There is a partial negative charge on the H atom. B Electrons are shared equally between the H and F atoms. C The bond is extremely weak. D The bond is highly polar.

D The bond is highly polar.

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 ? A The solubility of MgF2 is less than that of NaF. B The electronegativity of Mg is greater than that of Na. C The mass of the Mg cation is greater than that of the Na cation. D The charge of the Mg cation is larger than that of the Na cation.

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

Diagram 1 above shows equimolar samples of two gases inside a container fitted with a removable barrier. Diagram 2 above shows the gases soon after the barrier is removed. Which statement describes the changes to the initial and the final partial pressure of each gas A The partial pressure of each gas in the mixture is double its initial pressure; the final total pressure is half the sum of the initial pressures B The partial pressure of each gas in the mixture is double its initial pressure; the final total pressure is twice the sum of the initial pressures of the two gases. C The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is half the sum of the initial pressures of the two gases. D The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is the same as the sum of the initial pressures of the two gases.

D The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is the same as the sum of the initial pressures of the two gases.

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? A All the atoms in molecule 1 lie in one plane. B All the molecules have the same empirical formula. C The C-C-C bond angle in molecule 2 is close to 180°. D The strongest carbon-to-carbon bond occurs in molecule 3.

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

The average kinetic energy of the gas molecules is A greatest in container A B greatest in container B C greatest in container C D the same in all three containers

D the same in all three containers

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

D)

What number of moles of O2 is needed to produce 14.2 grams of P4O10 from P? (Molecular weight P4O10 = 284) A) 0.0500 mole B) 0.0625 mole C) 0.125 mole D) 0.250 mole E) 0.500 mole

D) 0.250 mole

Which of the following represents a pair of isotopes? Atomic Number / Mass Number A) 6/14 and 7/14 B) 6/7 and 14/14 C) 6/14 and 14/28 D) 7/13 and 7/14 E) 8/10 and 16/20

D) 7/13 and 7/14

A sample of CaCO3 (molar mass 100. g) was reported as being 30. percent Ca. Assuming no calcium was present in any impurities, the percent of CaCO3 in the sample is A) 30% B) 40% C) 70% D) 75% E) 100%

D) 75%

Which of the following correctly identitifis 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

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? A) Nitrogen atoms have a half-filled p subshell. B) There are more electron-electron repulsions in oxygen atoms than in nitrogen atoms. C) Electrons in the p subshell of oxygen atoms provide more shielding than electrons in the p subshell of nitrogen atoms. D) Nitrogen atoms have a smaller nuclear charge than oxygen atoms.

D) Nitrogen atoms have a smaller nuclear charge than oxygen atoms.

Which of the following best helps to explain why the electron affinity of Br has a greater magnitude than that of I? A) Br has a lower electronegativity than I does B) Br has a lower ionization energy than I does C) An added electron would go into a new shell in Br but not in I D) There is a greater attraction between an added electron and the nucleus in Br than in I.

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

RbCl has a high boiling point. Which of the following compounds is also likely to have a high boiling point, and why? A). NO, because its elements are in the same period of the periodic table. B). ClF , because its elements are in the same group of the periodic table. C). Cl2O , because its elements have similar electronegativities and it is a covalent compound. D). CsCl , because its elements have very different electronegativities and it is an ionic compound.

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

A student has a 1 g sample of each of the following compounds: NaCl, KBr, and KCl. Which of the following lists the samples in order of increasing number of moles in the sample? A. NaCl < KCl < KBr B. NaCl < KBr < KCl C. KCl < NaCl < KBr D. KBr < KCl < NaCl

D. KBr < KCl < NaCl

A flask contains 0.25 mole of SO2(g), 0.50 mole of CH4(g), and 0.50 mole of O2(g). The total pressure of the gases in the flask is 800 mm Hg. What is the partial pressure of the SO2(g) in the flask? A 800 mm Hg B 600 mm Hg C 250 mm Hg D 200 mm Hg E 160 mm Hg

E 160 mm Hg

A sample of an unknown gas from a cylinder is collected over water in the apparatus shown above. After all the gas sample has been collected, the water levels inside and outside the gas collection tube are made the same. Measurements that must be made to calculate the molar mass of the gas include all of the following EXCEPT A atmospheric pressure B temperature of the water C volume of gas in the gas-collection tube D initial and final mass of the gas cylinder E mass of the water in the apparatus

E mass of the water in the apparatus

Which of the following is the electron configuration of an excited atom that is likely to emit a quantum of energy? A) 1s2 2s2 2p6 3s2 3p1 B) 1s2 2s2 2p6 3s2 3p5 C) 1s2 2s2 2p6 3s2 D) 1s2 2s2 2p6 3s1 E) 1s2 2s2 2p6 3s1 3p1

E) 1s2 2s2 2p6 3s1 3p1

Equal masses of He and Ne are placed in a sealed container. What is the partial pressure of He if the total pressure in the container is 6 atm? A) 1 atm B) 2 atm C) 3 atm D) 4 atm E) 5 atm

E) 5 atm

Which of the following properties generally decreases across the periodic table from sodium to chlorine? A) First ionization energy B) Atomic Mass C) Electronegativity D) Maximum value of oxidation number E) Atomic radius

E) Atomic radius

Which of the following ions has the same number of electrons as Br- A) Ca2+ B) K+ C) Sr2+ D) I- E) Cl-

E) Cl-

1s2 2s22p63s23p3 Atoms of an element, X, have the electronic configuration shown above. The compound most likely formed with magnesium, Mg, is A) MgX B) Mg2X C) MgX2 D) MgX3 E) Mg3X2

E) Mg3X2

The elements in which of the following have most nearly the same atomic radius A.) Be, B, C, N B.) Ne, At, Kr, Xe C.) Mg, Ca, Sr, Ba D.) C, P, Se, I E.) Cr, Mn Fe, Co

E.) Cr, Mn Fe, Co

Two different ionic compounds each contain only copper and chlorine. Both compounds are powders, one white and one brown. An elemental analysis is performed on each powder. Which of the following questions about the compounds is most likely to be answered by the results of the analysis? a) What is the density of each pure compound? b) What is the formula unit of each compound c) What is the chemical reactivity of each compound d) Which of the two compounds is more soluble to water

b) What is the formula unit of each compound

A student combines a solution of NaCl(aq) with a solution of AgNO3(aq), and a precipitate forms. Which of the following is the balanced net ionic equation for forming the precipitate? A Ag+(aq)+Cl−(aq)→AgCl(s) B Na+(aq)+NO3−(aq)→NaNO3(s) C NaCl(aq)+AgNO3(aq)→NaNO3(s)+AgCl(aq) D NaCl(aq)+AgNO3(aq)→NaNO3(s)+AgCl(s)

A Ag+(aq)+Cl−(aq)→AgCl(s)

A student combined two colorless aqueous solutions. One of the solutions contained Na2CO3 as the solute, and the other contained HCl. The chemical reaction that took place is represented by the equation above. What experimental result would be evidence that a chemical reaction took place when the solutions were combined? A Bubbles formed when the two solutions were combined. B The total volume of the mixture is close to the sum of the initial volumes. C The resulting solution is colorless. D The resulting solution conducts electricity.

A Bubbles formed when the two solutions were combined.

Zn(s)+CuSO4(aq)→Cu(s)+ZnSO4(aq) When a zinc plate is placed in an aqueous solution of copper sulfate, elemental copper forms, as represented by the equation above. Which of the following represents the reduction half-reaction of the reaction? A Cu2+(aq)+2e−→Cu(s) B Cu(s)→Cu2+(aq)+2e− C Zn(s)+2e−→Zn2−(aq) D Zn(s)→Zn22+(aq)+2e-

A Cu2+(aq)+2e−→Cu(s)

A student carried out a titration using HC2H3O2(aq) and NaOH(aq). The net ionic equation for the neutralization reaction that occurs during the titration is represented above. The NaOH(aq) was added from a buret to the HC2H3O2(aq) in a flask. The equivalence point was reached when a total of 20.0mL of NaOH(aq) had been added to the flask. How does the amount of HC2H3O2(aq) in the flask after the addition of 5.0mL of NaOH(aq) compare to the amount of HC2H3O2(aq) in the flask after the addition of 1.0mL of NaOH(aq), and what is the reason for this result? A It is less because more HC2H3O2(aq) reacted with the base. B It is the same because the equivalence point has not been reached. C It is the same because all of the coefficients in the neutralization equation are 1. D It is greater because HC2H3O2(aq) is a proton donor.

A It is less because more HC2H3O2(aq) reacted with the base

A student adds 50.0g of liquid water at 25.0°C to an insulated container fitted with a temperature probe. The student then adds 10.0g of ice at 0.0°C, closes the container, and measures the temperature at different intervals. Which of the following best explains why the student's prediction is correct? A The H2O molecules initially in the ice and the molecules initially in the liquid will have the same average kinetic energy. B The transfer of energy between the H2O molecules in the ice and liquid water stops once all the molecules are in the liquid phase. C Once all of the H2O molecules are in the liquid phase, the individual molecular speeds either increase or decrease until all the particles have the same speed. D Once all of the H2O molecules are in the liquid phase, collisions between them virtually stop as they reach an equilibrium distance from their neighboring molecules.

A The H2O molecules initially in the ice and the molecules initially in the liquid will have the same average kinetic energy.

An advertisement for a commercial hand warmer claims that the hand warmer works because a chemical reaction in the hand warmer draws out the body's own natural heat, causing a warming effect. A The advertisement's claim is inaccurate because heat flowing from the hands to the warmer would only happen if the chemical reaction was endothermic, which would cause the hands to feel colder. B The advertisement's claim is inaccurate because heat flowing from the hands to the warmer would only happen if the chemical reaction was exothermic, which would cause the hands to feel colder. C The advertisement's claim is accurate because heat flowing from the hands to the warmer would only happen if the chemical reaction was endothermic, which would cause the hands to feel warmer. D The advertisement's claim is accurate because heat flowing from the hands to the warmer would only happen if the chemical reaction was exothe

A The advertisement's claim is inaccurate because heat flowing from the hands to the warmer would only happen if the chemical reaction was endothermic, which would cause the hands to feel colder.

In a lab, a student is given a 21g 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

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

Ar(g) deviates more from ideal behavior at extremely high pressures than Ne(g) does. Which of the following is one reason for this difference? A The particle volume of Ar is greater than that of Ne. B Ar atoms have more valence electrons than Ne atoms have, so Ar atoms have greater interparticle forces. C The intermolecular forces between Ne atoms are greater than those between Ar atoms. D Ar atoms are more attracted to the walls of the container than Ne atoms are.

A The particle volume of Ar is greater than that of Ne.

A student was given two clear liquids; a colorless liquid and a dark-blue liquid. The student was asked to combine the liquids in a beaker and record observations. Which of the following results, if true, would provide the best evidence that a chemical change took place when the liquids were combined? A The resulting mixture was cloudy. B The total volume of the mixture was equal to the sum of the initial volumes. C The resulting liquid was light blue. D The liquids formed two separate layers in the beaker.

A The resulting mixture was cloudy.

A student has two samples of NaCl, each one from a different source. Assume that the only potential contaminant in each sample is KCl. The student runs an experiment to determine the percent by mass of chlorine in each sample. From the results of this experiment alone, which of the following questions is most likely to be answered? A Which sample has the higher purity? B Which sample has the higher density? C What is the source of the contaminants present in each of the samples? D Which sample came from a salt mine, and which sample came from the ocean?

A Which sample has the higher purity?

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)

The graph above shows the changes in temperature recorded for the 2.00 L of H2O surrounding a constant-volume container in which a 1.00 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 H2O is 1.00g/mL, and that the specific heat capacity of H2O is about 4.2J/g⋅°C. Based on this information, estimate how much heat was released from the combustion of the benzoic acid sample. A 0.013kJ B 25kJ C 180kJ D 210kJ

B 25kJ

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.

Which of the following best describes the process represented above that takes place when NH3 is added to water? A It is a single replacement reaction in which an electron pair on N is replaced with an H atom. B It is an acid-base reaction in which a proton is exchanged from H2O to NH3. C It is a precipitation reaction in which NH4OH, an insoluble solid, is produced. D It is an oxidation-reduction reaction in which the oxidation number of N changes from −3 to −4.

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

Mass 27.3g Mass Percent of Na 35.2% Density 2.05g cm−3 Color White 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 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? A Al with 13 neutrons B Mg with 14 neutrons C Fe with 26 neutrons D Ti with 26 neutrons

B Mg with 14 neutrons

Which of the following is the correct net ionic equation of the reaction that occurs when aqueous solutions of ammonia and hydrochloric acid are combined? A NH3(aq)+HCl(aq)→NH4Cl(aq) B NH3(aq)+H+(aq)→NH4+(aq) C NH3(aq)+HCl(aq)→NH4+(aq)+Cl−(aq) D NH3(aq)+H+(aq)+Cl-(aq)→NH4+(aq)+Cl−(aq)

B NH3(aq)+H+(aq)→NH4+(aq)

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 s sublevel than in a p sublevel.

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

Two aqueous NaCl solutions of equal volume and concentration were kept in flasks and held at different temperatures. Based on this information, which of the following predictions is correct? A The average kinetic energy of the particles in the cooler solution will decrease as they collide with the particles from the warmer solution. B The average kinetic energy of the particles in the cooler solution will increase as they collide with the particles from the warmer solution. C The particles from the cooler solution and the particles from the warmer solution will reach thermal equilibrium through collisions, at which time the average kinetic energy of the particles in the mixture will be lower D The particles from the cooler solution and the particles from the warmer solution will reach thermal equilibrium through collisions, at which time the average kinetic energy of the particles in the mixture will be higher

B The average kinetic energy of the particles in the cooler solution will increase as they collide with the particles from the warmer solution.

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? A The gas in sample 1 would deviate more from ideal behavior because the average distance an Xe atom travels before colliding with another Xe atom is greater. 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. C The gas in sample 2 would deviate more from ideal behavior because the average speed of the Xe atoms is less, leading to an increase in intermolecular attractions. D The gases in both sample 1 and sample 2 would show the same deviation from ideal behavior.

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.

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 2s 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 2s subshell.

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.

Two different ionic compounds each contain only copper and chlorine. Both compounds are powders, one white and one brown. An elemental analysis is performed on each powder. Which of the following questions about the compounds is most likely to be answered by the results of the analysis? A What is the density of each pure compound? B What is the formula unit of each compound? C What is the chemical reactivity of each compound? D Which of the two compounds is more soluble in water?

B What is the formula unit of each compound?

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?

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)

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

B)

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

B)

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.

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

Which of the following numerical expressions gives the number of particles in 2.0g of Ne? A 6.0×1023particles/mol2.0g B 6.0×1023particles/mol20.18g/mol C 2.0g/20.18g/mol(6.0×1023particles/mol) D 20.18g/mol/(2.0g)(6.01023 particles/mol)

C 2.0g20.18g/mol(6.0×1023particles/mol)

Al(s)→Al3+(aq)+3e− Sn2+(sq)+2e−→Sn(s) Based on the half-reactions represented above, which of the following is the balanced ionic equation for the oxidation-reduction reaction between Al(s) and Sn2+(aq) ? A Al(s)+Sn2+(aq)→Al3+(aq)+Sn(s)+e− B 3Al(s)+2Sn2+(aq)→3Al3+(aq)+2Sn(s) C 2Al(s)+3Sn2+(aq)→2Al3+(aq)+3Sn(s) D Al(s)+Sn2+(aq)+2e−→Al3+(aq)+Sn(s)+3e−

C 2Al(s)+3Sn2+(aq)→2Al3+(aq)+3Sn(s)

1234567Total mass of sample (g)Mass of C in sample (g)Mass of Mg in sample (g)Mass of Ca in sample (g)Molar mass of C (g/mol)Molar mass of Mg (g/mol)Molar mass of Ca (g/mol)98.512.02.436.112.024.340.1 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? A 1, 2, 5 B 2, 5, 6 C 3, 4, 6, 7 D 2, 3, 4, 5

C 3, 4, 6, 7

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 A physical change occurred when a new yellow compound was formed. B A physical change occurred when the color of the NaI solid added changed to yellow when mixed with water. C A chemical change occurred when a yellow, insoluble compound with a larger mass than the original NaI formed. D A chemical change occurred when covalent bonds between the yellow solid and water were broken during drying.

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

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? A A neutral atom of the element contains exactly two electrons. B The element does not react with other elements to form compounds. C In its compounds, the element tends to form ions with a charge of +1. D In its compounds, the element tends to form ions with a charge of +3.

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

A chemistry teacher carried out several demonstrations, and students recorded their observations. For one of the demonstrations, a student concluded that a physical change took place, but not a chemical change. Which of the following observations could the student have made of the results of the demonstration? A Two colorless solutions were combined, and the resulting solution was pink. B When a solid was added to a liquid, sparks were produced. C One piece of solid substance was changed into small pieces. D When two solutions were combined, a precipitate formed.

C One piece of solid substance was changed into small pieces.

According to the balanced chemical equation above, when 100.0mL of 0.100M K2SO3(aq) is mixed with 100.0mL of 0.200M HNO3(aq) at 30°C and 1 atm, the volume of SO2 gas produced is 0.24 L. If it is assumed that the reaction goes to completion, which of the following changes would double the volume of SO2 produced at the same temperature and pressure, and why? (For each change, assume that the other solutions and volumes remain the same.) A Using 200.0mL of the 0.100M K2SO3(aq), because it then becomes the reactant in excess B Using 200.0mL of the 0.200M HNO3(aq), because the volume of SO2 produced is inversely proportional C Using 200.0mL of 0.100M K2SO3(aq) and 200.0mL of 0.200M HNO3(aq), because this provides double the number of moles with the correct stoichiometric ratio D Using 400.0mL of 0.100M K2SO3(aq) and 200.0mL of 0.200M HNO3(aq), because this provides the same number of moles of each reactant

C Using 200.0mL of 0.100M K2SO3(aq) and 200.0mL of 0.200M HNO3(aq), because this provides double the number of moles with the correct stoichiometric ratio

Which of the following best helps explain why the electronegativity of Cl is less than that of F? A The mass of the Cl atom is greater than the mass of the F atom. B The Cl nucleus contains more protons than the F nucleus contains. C When Cl and F form bonds with other atoms, the Cl bonding electrons are more shielded from the positive Cl nucleus than the F bonding electrons are shielded from the positive F nucleus. D Because Cl is larger than F, the repulsions among electrons in the valence shell of Cl are less than the repulsions among electrons in the valence shell of F.

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

Which of the following best represents the ground-state electron configuration for an atom of selenium? A) 1s2 2s2 2p6 3s2 3p6 B) 1s2 2s2 2p6 3s2 3p4 C) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4 D) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

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

An equimolar mixture of N2(g) and Ar(g) is kept inside a rigid container at a constant temperature of 300 K. The initial partial pressure of Ar in the mixture is 0.75atm. An additional amount of Ar was added to the container, enough to double the number of moles of Ar gas in the mixture. Assuming ideal behavior, what is the final pressure of the gas mixture after the addition of the Ar gas? A 0.75atm, because increasing the partial pressure of Ar decreases the partial pressure of N2. B 1.13atm, because 33% of the moles of gas are N2. C 1.50atm, because the number of moles of N2 did not change. D 2.25atm, because doubling the number of moles of Ar doubles its partial pressure.

D 2.25atm, because doubling the number of moles of Ar doubles its partial pressure.

For a classroom demonstration, a chemistry teacher puts samples of two different pure solid powders in a beaker. The teacher places the beaker on a small wooden board with a wet surface, then stirs the contents of the beaker. The teacher asks the students to make a claim about the observation and to justify their claims. Which of the following is the best claim and justification based on the students' observation? A An exothermic chemical change occurred because heat flowed from the contents of the beaker to the room. B An exothermic physical change occurred because heat flowed from the contents of the beaker and the water on the board to the room. C An endothermic physical change occurred because the freezing of water is an endothermic process. D An endothermic chemical change occurred because the temperature of the beaker and the water on the board decreased as heat was absorbed by the reaction.

D An endothermic chemical change occurred because the temperature of the beaker and the water on the board decreased as heat was absorbed by the reaction.

A piece of Fe(s) at 25°C is placed into H2O(l) at 75°C in an insulated container. A student predicts that when thermal equilibrium is reached, the Fe atoms, being more massive than the H2O molecules, will have a higher average kinetic energy than the H2O molecules. Incorrect? A At thermal equilibrium, the less massive H2O molecules would have a higher average kinetic energy than the Fe atoms because they are more free to move than are the Fe atoms. B At thermal equilibrium, the collisions between the Fe atoms and the H2O molecules would cease C At thermal equilibrium, the movement of both the Fe atoms and the H2O molecules would cease D At thermal equilibrium, the average kinetic energy of the Fe atoms cannot be greater than that of the H2O molecules; the average kinetic energies must be the same according to the definition of thermal equilibrium.

D At thermal equilibrium, the average kinetic energy of the Fe atoms cannot be greater than that of the H2O molecules; the average kinetic energies must be the same according to the definition of thermal equilibrium.

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? A K, because it is in the same group as Na. B Mg, because its mass is similar to that of Na. C Ar, because its mass is similar to that of Cl. D Br, because it has the same number of valence electrons as Cl.

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

A beaker was half filled with freshly distilled H2O and placed on a hot plate. As the temperature of the water reached 100°C, vigorous bubbling was observed in the beaker. The gaseous contents of the bubbles were analyzed. The presence of which of the following substances would support the claim that the observed phenomenon was a physical change? A H2(g) B O2(g) C CO2(g) D H2O(g)

D H2O(g)

Which of the following is the correct net ionic equation of the neutralization reaction between hydrofluoric acid and sodium hydroxide in aqueous solution? A HF(aq)+NaOH(aq)→H2O(l)+NaF(aq) B HF(aq)+NaOH(aq)→NaH(aq)+FOH(aq) C H+(aq)+OH−(aq)→H2O(l) D HF(aq)++OH−(aq)→H2O(l)+F-(aq)

D HF(aq)++OH−(aq)→H2O(l)+F-(aq)

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.

When the reaction represented above proceeds, heat is produced. Which of the following best describes the reaction? A It is a combustion reaction because heat is produced by the reaction. B It is a double replacement reaction because 2Cl atoms are added to Zn. C It is an acid-base reaction because HCl is an acid that is capable of exchanging H+. D It is an oxidation-reduction reaction because zinc is oxidized and hydrogen is reduced.

D It is an oxidation-reduction reaction because zinc is oxidized and hydrogen is reduced.

A student has a 1g sample of each of the following compounds: NaCl, KBr, and KCl. Which of the following lists the samples in order of increasing number of moles in the sample? A NaCl<⁢KCl⁢<KBr B NaCl<KBr⁢<KCl C KCl<NaCl⁢<KBr D KBr<KCl<NaCl

D KBr<KCl<NaCl

Sample 1 and 2 Initial Volume (mL) 125.0 36.0 Initial Temperature (C∘) 250.0 18.0 The table provides data for two CH3OH(l) samples. Describes what happens when these samples are initially mixed, and why? A Thermal energy is transferred between the CH3OH molecules in sample 1 and the CH3OH molecules in sample 2 because both samples contain the same substance. B The CH3OH molecules from sample 2 transfer thermal energy to the CH3OH molecules from sample 1 through collisions because there are more moles of molecules in sample 2. C The CH3OH molecules from sample 1 transfer thermal energy to the CH3OH molecules from sample 2 through collisions because sample 1 has a higher density. 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.

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.

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.

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? A The leftmost peak represents the valence electrons. B The two peaks at the right represent a total of three electrons. C The electrons in the 1s sublevel have the smallest binding energy. D The electrons in the 2p sublevel have the smallest binding energy.

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

In the spring, blossoms on cherry trees can be damaged when temperatures fall below −2°C. When the forecast calls for air temperatures to be below −5°C for a few hours one night, a farmer sprays his blossoming cherry trees with water, claiming that the blossoms will be protected by the water as it freezes. Which of the following is a correct scientific justification? A Water on the blossoms will not freeze unless the air temperature falls significantly below −5°C. B Water is a good thermal conductor that transfers heat from the cold air to the blossoms, keeping the blossoms from going below −2°C. C The freezing of water is an endothermic process; thus, water that freezes on the blossoms absorbs heat from the atmosphere, which in turn keeps the blossoms above 0°C. D The freezing of water is an exothermic process; thus, water that freezes on the blossoms releases heat to keep the blossoms at or above −2

D The freezing of water is an exothermic process; thus, water that freezes on the blossoms releases heat to keep the blossoms at or above −2°C.

5.0g sample of MgCl2 may contain measurable amounts of other compounds as impurities. Which of the following quantities is (are) needed to determine that the sample is pure MgCl2 ? A The color and density of the sample B The mass of Mg in the sample only C The number of moles of Cl in the sample only D The mass of Mg and the mass of Cl in the sample

D The mass of Mg and the mass of Cl in the sample

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? A The densities of the gases, because as the density of a gas increases, the average speed of its molecules decreases. B The pressures of the gases, because the pressure exerted by a gas depends on the average speed with which its molecules are moving. C The volumes of the gases, because at a fixed temperature the volume of a gas can be calculated using the equation PV = nRT. 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=1/2mv2

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=1/2mv2.

Which of the following best helps to explain why the electron affinity of Br has a greater magnitude than that of I? A Br has a lower electronegativity than I does. B Br has a lower ionization energy than I does. C An added electron would go into a new shell in Br but not in I. D There is a greater attraction between an added electron and the nucleus in Br than in I.

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

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?

A student combines a solution of NaCl(aq) with a solution of AgNO3(aq), and a precipitate forms. Assume that 50.0mL of 1.0M NaCl(aq) and 50.0mL of 1.0M AgNO3(aq) were combined. According to the balanced equation, if 50.0mL of 2.0M NaCl(aq) and 50.0mL of 1.0M AgNO3(aq) were combined, the amount of precipitate formed would A double, because all of the coefficients are 1 B double, because the amount of one of the reactants was doubled C not change, because all of the coefficients are 1 D not change, because the amount of AgNO3(aq) did not change

D not change, because the amount of AgNO3(aq) did not change

For an experiment, 50.0g of H2O was added to a coffee-cup calorimeter, as shown in the diagram above. The initial temperature of the H2O was 22.0°C, and it absorbed 300.J of heat from an object that was carefully placed inside the calorimeter. Assuming no heat is transferred to the surroundings, which of the following was the approximate temperature of the H2O after thermal equilibrium was reached? Assume that the specific heat capacity of H2O is 4.2J/(g⋅K). A 21.3°C B 22.0°C C 22.7°C D 23.4 °C

D 23.4 °C

Which of the following ground-state electron configurations represents the atom that has the lowest first-ionization energy? A) 1s2 2s1 B) 1s2 2s2 2sp2 C) 1s2 2s2 2p6 D) 1s2 2s2 2p6 3s1

D) 1s2 2s2 2p6 3s1

The graphs above show Maxwell-Boltzmann distributions for one-mole samples of Ar(g). Graph 1 shows the distribution of particle energies at 300⁢K and graph 2 shows the distribution of particle energies at 600K. A student predicts that if the samples are combined in an insulated container and thermal equilibrium is attained, then the most probable particle energy will be between the most probable energy shown in graph 1 and the most probable energy shown in graph 2. Which of the following is the best justification for the student's claim?

D) When the samples are combined, the gas particles will collide with one another, with the net effect being that energy will be transferred from the more energetic particles to the less energetic particles until a new distribution of energies is achieved at a temperature between 300K and 600K.