Chemistry 3.1-3.6

The boiling points of the elements helium, neon, argon, krypton, and xenon increase in that order. Which of the following statements accounts for this increase? .A The London (dispersion) forces increase B The hydrogen bonding increases. C The dipole-dipole forces increase. D The chemical reactivity increases. E The number of nearest neighbors increases.

A The London (dispersion) forces increase

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 graph above shows the speed distribution of molecules in a sample of a gas at a certain temperature. Which of the following graphs shows the speed distribution of the same molecules at a lower temperature (as a dashed curve) ?

D

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

In which of the following liquids do the intermolecular forces include dipole-dipole forces? A F2(l) B CH4(l) C CF4(l) D CH2F2(l)

D CH2F2(l)

On the basis of strength of intermolecular forces, which of the following elements would be expected to have the highest melting point? A Br2 B Cl2 C F2 D Kr E N2

D Kr

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

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 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(1.85)(0.0821)(308)3.00 atm B (1.85)(35.0)(0.0821)(3.00) atm(1.85)(35.0)(0.0821)(3.00) atm C 3.00(1.85)(0.0821)(308) atm3.00(1.85)(0.0821)(308) atm D (1.85)(8.314)(308)3.00 atm(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(1.85)(0.0821)(308)3.00 atm

The following questions refer to the below. The table below contains information about samples of four different gases at 273 K. The samples are in four identical rigid containers numbered 1 through 4. 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

The London (dispersion) forces are weakest for which of the following gases under the same conditions of temperature and pressure? A H2 B O2 C Xe D F2 E N2

A H2

The experimental apparatus represented above is used to demonstrate the rates at which gases diffuse. When the cotton balls are placed in the ends of a tube at the same time, the gases diffuse from each end and meet somewhere in between, where they react to form a white solid. Which of the following combinations will produce a solid closest to the center of the tube? A HCl and CH3NH2 B HCl and NH3 C HBr and CH3NH2 D HBr and NH3

A HCl and CH3NH2

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.

A sample of a hard, solid binary compound at room temperature did not conduct electricity as a pure solid but became highly conductive when dissolved in water. Which of the following types of interactions is most likely found between the particles in the substance? A Ionic bonds B Metallic bonds C Covalent bonds D Hydrogen bonds

A Ionic bonds

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 NH3NH3 molecules are polar while CH4CH4 molecules are not, and the greater attractions between NH3NH3 molecules cause the molecules to collide with the walls of the container with less force. B NH3NH3 molecules have a greater molar mass than CH4CH4 molecules, so the NH3NH3 molecules collide with the walls of the container with more force. C CH4CH4 molecules have more hydrogen atoms than NH3NH3 molecules, so CH4CH4 molecules have more hydrogen bonding and greater intermolecular forces. D CH4CH4 molecules are larger than NH3NH3 molecules, so the actual CH4CH4 molecules take up a significant portion of the volume of the gas.

A NH3NH3 molecules are polar while CH4CH4 molecules are not, and the greater attractions between NH3NH3 molecules cause the molecules to collide with the walls of the container with less force.

Based on the data in the tables above, which of the following statements provides the best prediction for the boiling point of NaCl ? A NaCl will have a lower boiling point than NaF because the coulombic attractions are weaker in NaCl than in NaF . B NaCl will have a boiling point between that of NaF and MgO because the covalent character of the bonds in NaCl is intermediate between that of MgO and NaF. C NaCl will have a higher boiling point than MgO because the ions are spaced farther apart in NaCl . D NaCl will have a higher boiling point than MgO because the energy required to transfer electrons from the anion to the cation is larger in NaCl than in MgO .

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

Equal numbers of moles of He(g), Ar(g), and Ne(g) are placed in a glass vessel at room temperature. If the vessel has a pinhole-sized leak, which of the following will be true regarding the relative values of the partial pressures of the gases remaining in the vessel after some of the gas mixture has effused? A PHe < PNe < PAr B PHe < PAr < PNe C PNe < PAr < PHe D PAr < PHe < PNe E PHe = PAr = PNe

A PHe < PNe < PAr

Which of the following gases deviates most from ideal behavior? A SO2 B Ne C CH4 D N2 E H2

A SO2

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

At 298 K and 1 atm, bromine is a liquid with a high vapor pressure, whereas chlorine is a gas. This provides evidence that, under these conditions, the A forces among Br2 molecules are greater than those among Cl2 molecules B forces among Br2 molecules are weaker than the Br—Br bond C forces among Cl2 molecules are stronger than the Cl—Cl bond D Br—Br bond is stronger than the Cl—Cl bond E Br—Br bond is weaker than the Cl—Cl bond

A forces among Br2 molecules are greater than those among Cl2 molecules

When the actual gas volume is greater than the volume predicted by the ideal gas law, the explanation lies in the fact that the ideal gas law does NOT include a factor for molecular. A volume B mass C velocity D attractions E shape

A volume

Based on the data in the table above, which of the following correctly predicts the relative strength of the attraction of Zn2+, Ca2+, and Ba2+ ions to water molecules in a solution, from strongest to weakest, and provides the correct reason? A.) Zn2+ > Ca2+ > Ba2+ because the smaller ions have a stronger coulombic attraction to water B.) Zn2+ > Ca2+ > Ba2+ because the smaller ions are more electronegative C.) Ba2+ > Ca2+ > Zn2+ because the larger ions are more polarizable D.) Ba2+ > Ca2+ > Zn2+ because the larger ions are less electronegative

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

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

The structure of one form of boron nitride is represented above. This form of boron nitride is one of the hardest substances known. Which of the following best helps explain why boron nitride is so hard? A Boron ions and nitrogen ions are held together by ionic bonds. B Boron nitride is a network solid of atoms connected by covalent bonds with fixed bond angles. C Boron nitride is an alloy, and alloys are typically harder than the elements used to make them. D Boron nitride is a polymer made of long chains of boron atoms and nitrogen atoms held together by dispersion forces.

B Boron nitride is a network solid of atoms connected by covalent bonds with fixed bond angles.

The table above shows the structural formulas and molar masses for three different compounds. Which of the following is a list of the compounds in order of increasing boiling points? A Butane < 1-propanol < acetone B Butane < acetone < 1-propanol C 1-propanol < acetone < butane D Acetone = butane < 1-propanol

B Butane < acetone < 1-propanol

The molecular formula and molar mass of two straight-chain hydrocarbons are listed in the table above. Based on the information in the table, which compound has the higher boiling point, and why is that compound's boiling point higher? A C4H10 ,because it has more hydrogen atoms, resulting in more hydrogen bonding B C4H10 , because it has more electrons, resulting in greater polarizability and stronger dispersion forces C C2H6 , because its molecules are smaller and they can get closer to one another, resulting in stronger dispersion forces D C2H6 , because its molecules are more polar, resulting in stronger dipole-dipole attractions

B C4H10 , because it has more electrons, resulting in greater polarizability and stronger dispersion forces

Based on the information in the table above, which liquid, CS2(l) or CCl4(l), has the higher equilibrium vapor pressure at 25°C, and why? A CS2(l), because it has stronger London dispersion forces B CS2(l), because it has weaker London dispersion forces C CCl4(l), because it has stronger London dispersion forces D CCl4(l), because it has weaker London dispersion forces

B CS2(l), because it has weaker London dispersion forces

The ionic compounds NaCl and MgS are represented by the diagrams above. Which statement correctly identifies diagram 1 and identifies the compound with the lower melting point, explaining why? A Diagram 1 represents NaClNaCl; it has a lower melting point than MgSMgS has because the coulombic attractions between the singly charged Na+Na+ ions and the Cl−Cl− ions in NaClNaCl are stronger than those between the ions in MgSMgS. B Diagram 1 represents NaClNaCl; it has a lower melting point than MgSMgS because the coulombic attractions between its singly charged Na+Na+ ions and the Cl−Cl− ions are weaker than those between the ions in MgSMgS. C Diagram 1 represents MgSMgS; it has a lower melting point than NaClNaCl because the coulombic attractions between its doubly charged Mg2+Mg2+ ions and the S2−S2− ions are stronger than those between the ions in NaClNaCl. D Diagram 1 represents MgSMgS; it has a lower melting point than NaClNaCl because the coulombic attractions between the doubly charged Mg2+Mg2+ ions and the S2−S2− ions are weaker than those between the ions in NaClNaCl.

B Diagram 1 represents NaClNaCl; it has a lower melting point than MgSMgS because the coulombic attractions between its singly charged Na+Na+ ions and the Cl−Cl− ions are weaker than those between the ions in MgSMgS.

Based on Coulomb's Law and the information in the table above, which of the following cations is most likely to have the weakest interaction with an adjacent water molecule in an aqueous solution? A Li+ B Na+ C Ca2+ D In3+

B Na+

Which of the following could be the identity of a white crystalline solid that exhibits the following properties? It melts at 320°C. It does not conduct electricity as a solid. It conducts electricity in an aqueous solution. A C6H12O6(s) B NaOH(s) C SiO2(s) D Cu(s)

B NaOH(s)

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 XeXe atom travels before colliding with another XeXe atom is greater. B The gas in sample 2 would deviate more from ideal behavior because the XeXe 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 XeXe 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 XeXe atoms are closer together, leading to an increase in intermolecular attractions.

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

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

Questions 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

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

Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits the statement. A choice may be used once, more than once, or not at all. The following questions refer to the 1 L flasks shown below. In which flask do the molecules have the greatest average speed? A.) A B.) B C.) C D.) D E.) E

B.) B

Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits the statement. A choice may be used once, more than once, or not at all. The following questions refer to the 1 L flasks shown below. Which flask contains the smallest number of moles of gas? A.) A B.) B C.) C D.) D E.) E

B.) B

Under which of the following conditions of temperature and pressure would 1.0 mol of the real gas CO2(g) behave most like an ideal gas?

C

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

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 0.010atm0.010atm, because there is 0.010mol0.010mol of H2H2 in the sample. B About 0.050atm0.050atm, because there is 0.050mol0.050mol of gases at 0°C0°C and 1.0atm1.0atm. C About 0.20atm0.20atm, because H2H2 comprises 20%20% of the total number of moles of gas. D About 0.40atm0.40atm, because the mole ratio of H2:O2:N2H2:O2:N2 is 0.4:0.6:10.4:0.6:1.

C About 0.20atm0.20atm, because H2H2 comprises 20%20% of the total number of moles of gas.

If the pressure of each gas is increased at constant temperature until condensation occurs, which gas will condense at the lowest pressure? A Methane B Ethane C Butane D All the gases will condense at the same pressure.

C Butane

Based on the data in the table above, which of the following liquid substances has the weakest intermolecular forces? A C6H6(l) B C2H5OH(l) C CH3OH(l) D C2H6O2(l)

C CH3OH(l)

A 2 L container will hold about 4 g of which of the following gases at 0°C and 1 atm? A SO2 B N2 C CO2 D C4H8 E NH3

C CO2

Which of the following is the strongest type of interaction that occurs between the atoms within the circled areas of the two molecules represented above? A Polar covalent bond B Nonpolar covalent bond C Hydrogen bond D London dispersion forces

C Hydrogen bond

The diagram above shows molecules of Br2 and I2 drawn to the same scale. Which of the following is the best explanation for the difference in the boiling points of liquid Br2 and I2, which are 59oC and 184oC, respectively? A Solid iodine is a network covalent solid, whereas solid bromine is a molecular solid. B The covalent bonds in I2 molecules are weaker than those in Br2 molecules. C I2 molecules have electron clouds that are more polarizable than those of Br2 molecules, thus London dispersion forces are stronger in liquid I2. D Bromine has a greater electronegativity than iodine, thus there are stronger dipole-dipole forces in liquid bromine than in liquid iodine.

C I2 molecules have electron clouds that are more polarizable than those of Br2 molecules, thus London dispersion forces are stronger in liquid I2.

A 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

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.

At room temperature I2(s) is a molecular solid. Which of the following provides a characteristic of I2(s) with a correct explanation? A It has a high melting point because it has weak intermolecular forces. B It is hard because it forms a threedimensional covalent network. C It is not a good conductor of electricity because its valence electrons are localized in bonding and nonbonding pairs. D It is very soluble in water because its molecules are polar.

C It is not a good conductor of electricity because its valence electrons are localized in bonding and nonbonding pairs.

Which statement best helps to explain the observation that NH3(l) boils at −28°C, whereas PH3(l) boils at −126°C? A The dispersion forces in NH3NH3 are weaker than the dispersion forces in PH3PH3. B The dispersion forces in NH3NH3 are stronger than the dipole-dipole forces in PH3PH3. C NH3NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3PH3. D NH3NH3 has hydrogen bonding that is weaker than the dipole-dipole forces in PH3PH3.

C NH3NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3PH3.

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.

Nonane and 2,3,4-trifluoropentane have almost identical molar masses, but nonane has a significantly higher boiling point. Which of the following statements best helps explain this observation? A The C-F is easier to break than the C-H bond. B The C-F is more polar than the C-H bond. C The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane. D The carbon chains are farther apart in a sample of nonane than they are in 2,3,4-trifluoropentane.

C The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane.

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? 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 of the two gases. 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.

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.

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

The best explanation for the fact that diamond is extremely hard is that diamond crystals A are made up of atoms that are intrinsically hard because of their electronic structures B consist of positive and negative ions that are strongly attracted to each other C are giant molecules in which each atom forms strong covalent bonds with all of its neighboring atoms D are formed under extreme conditions of temperature and pressure E contain orbitals or bands of delocalized electrons that belong not to single atoms but to each crystal as a whole

C are giant molecules in which each atom forms strong covalent bonds with all of its neighboring atoms

Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits the statement. A choice may be used once, more than once, or not at all. 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

Nonane and 2,3,4-trifluoropentane have almost identical molar masses, but nonane has a significantly higher boiling point. Which of the following statements best helps explain this observation? A.) The C-F bond is easier to break than the C-H bond. B.) The C-F bond is more polar than the C-H bond. C.) The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane. D.) The carbon chains are farther apart in a sample of nonane than they are in 2,3,4- trifluoropentane.

C.) The carbon chains are longer in nonane than they are in 2,3,4-trifluoropentane.

Thymine and adenine form a base pair in the DNA molecule. These two bases can form a connection between two strands of DNA via two hydrogen bonds. Which of the following diagrams shows the correct representation of the hydrogen bonding (denoted by dashed lines) between thymine and adenine base pairs? (In each diagram, thymine is shown at the left and adenine is shown at the right. The bases are attached to the backbone portion of the DNA strands.)

D

Given that the density of Hg(l) at 0°C is about 14 g mL-1, which of the following is closest to the volume of one mole of Hg(l) at this temperature? A 0.070 mL B 0.14 mL C 1.4 mL D 14 mL E 28 mL

D 14 mL

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 0.75atm0.75atm, because increasing the partial pressure of ArAr decreases the partial pressure of N2N2. B 1.13atm1.13atm, because 33%33% of the moles of gas are N2N2. C 1.50atm1.50atm, because the number of moles of N2N2 did not change. D 2.25atm2.25atm, because doubling the number of moles of ArAr doubles its partial pressure.

D 2.25atm2.25atm, because doubling the number of moles of ArAr doubles its partial pressure.

In which of the following processes are covalent bonds broken? A I2(s) → I2(g) B CO2(s) → CO2(g) C NaCl(s) → NaCl(l) D C(diamond) → C(g) E Fe(s) → Fe(l)

D C(diamond) → C(g)

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 F2F2 is soluble in water, whereas HFHF is insoluble in water. B The F2F2 molecule has a greater mass than the HFHF molecule has. C Liquid F2F2 has weak dispersion force attractions between its molecules, whereas liquid HFHF has strong ionic interactions between H+H+ and F−F− ions. D Liquid F2F2 has weak dispersion force attractions between its molecules, whereas liquid HFHF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.

D Liquid F2F2 has weak dispersion force attractions between its molecules, whereas liquid HFHF has both weak dispersion force attractions and hydrogen bonding interactions between its 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.

At constant temperature, the behavior of a sample of a real gas more closely approximates that of an ideal gas as its volume is increased because the A collisions with the walls of the container become less frequent B average molecular speed decreases C molecules have expanded D average distance between molecules becomes greater E average molecular kinetic energy decreases

D average distance between molecules becomes greater

In the diagram above, which of the labeled arrows identifies hydrogen bonding in water? A.) A B.) B C.) C D.) D

D.) D

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.

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 lists the substances F2, HCl, and HF in order of increasing boiling point? A HF < HCl < F2 B HF < F2 < HCl C HCl < F2 < HF D HCl < HF < F2 E F2 < HCl < HF

E F2 < HCl < HF

The liquefied hydrogen halides have the normal boiling points given above. The relatively high boiling point of HF can be correctly explained by which of the following? A HF gas is more ideal. B HF is the strongest acid. C HF molecules have a smaller dipole moment. D HF is much less soluble in water. E HF molecules tend to form hydrogen bonds.

E HF molecules tend to form hydrogen bonds.

In solid methane, the forces between neighboring CH4 molecules are best characterized as A ionic bonds B covalent bonds C hydrogen bonds D ion-dipole forces E London (dispersion) forces

E London (dispersion) forces

A certain crystalline substance that has a low melting point does not conduct electricity in solution or when melted. This substance is likely to be A a covalent network solid B a metallic solid C a polymer D an ionic solid E a molecular solid

E a molecular solid

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