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- 1. Multiple Choice
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 covalent network solid
a metallic solid
a polymer
an ionic solid
a molecular solid
- 2. Multiple Choice
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?
Ionic bonds
Metallic bonds
Covalent bonds
Hydrogen bonds
- 3. Multiple Choice
A student is given a sample of a pure, white crystalline substance. Which of the following would be most useful in providing data to determine if the substance is an ionic compound?
Examining the crystals of the substance under a microscope
Determining the density of the substance
Testing the electrical conductivity of the crystals
Testing the electrical conductivity of an aqueous solution of the substance
- 4. Multiple Choice
At 298 K and 1 atm, Br2 is a liquid with a high vapor pressure, and Cl2 is a gas. Those observations provide evidence that under the given conditions, the
forces among Br2 molecules are stronger than those among Cl2 molecules
forces among Cl2 molecules are stronger than the Cl−Cl bond
Br−Br bond is stronger than the Cl−Cl bond
Cl−Cl bond is stronger than the Br−Br bond
- 5. Multiple Choice
At room temperature I2(s) is a molecular solid. Which of the following provides a characteristic of I2(s) with a correct explanation?
It has a high melting point because it has weak intermolecular forces.
It is hard because it forms a threedimensional covalent network.
It is not a good conductor of electricity because its valence electrons are localized in bonding and nonbonding pairs.
It is very soluble in water because its molecules are polar.
- 6. Multiple Choice
Based on the data in the table above, which of the following liquid substances has the weakest intermolecular forces?
C6H6(l)
C2H5OH(l)
CH3OH(l)
C2H6O2(l)
- 7. Multiple Choice
Which statement best helps to explain the observation that NH3(l) boils at -28oC, whereas PH3(l) boils at -126oC?
The dispersion forces in NH3 are weaker than the dispersion forces in PH3.
The dispersion forces in NH3 are stronger than the dipole-dipole forces in PH3.
NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3.
NH3 has hydrogen bonding that is weaker than the dipole-dipole forces in PH3.
- 8. Multiple Choice
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?
F2 is soluble in water, whereas HF is insoluble in water.
The F2 molecule has a greater mass than the HF molecule has.
Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HF has strong ionic interactions between H+ and F- ions.
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.
- 9. Multiple Choice
In solid methane, the forces between neighboring CH4 molecules are best characterized as
ionic bonds
covalent bonds
hydrogen bonds
ion-dipole forces
London (dispersion) forces
- 10. Multiple Choice
In the diagram above, which of the labeled arrows identifies hydrogen bonding in water?
A
B
C
D
- 11. Multiple Choice
In which of the following liquids do the intermolecular forces include dipole-dipole forces?
F2(l)
CH4(l)
CF4(l)
CH2F2(l)
- 12. Multiple Choice
In which of the following processes are covalent bonds broken?
I2(s) → I2(g)
CO2(s) → CO2(g)
NaCl(s) → NaCl(l)
C(diamond) → C(g)
Fe(s) → Fe(l)
- 13. Multiple Choice
Ne, HF, C2H6, CH4
Which of the substances listed above has the highest boiling point, and why?
Ne, because its atoms have the largest radius
HF, because its molecules form hydrogen bonds
C2H6 , because each molecule can form multiple hydrogen bonds
CH4 , because its molecules have the greatest London dispersion forces
- 14. Multiple Choice
On the basis of strength of intermolecular forces, which of the following elements would be expected to have the highest melting point?
Br2
Cl2
F2
Kr
N2
- 15. Multiple Choice
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?
Boron ions and nitrogen ions are held together by ionic bonds.
Boron nitride is a network solid of atoms connected by covalent bonds with fixed bond angles.
Boron nitride is an alloy, and alloys are typically harder than the elements used to make them.
Boron nitride is a polymer made of long chains of boron atoms and nitrogen atoms held together by dispersion forces.
- 16. Multiple Choice
The best explanation for the fact that diamond is extremely hard is that diamond crystals
are made up of atoms that are intrinsically hard because of their electronic structures
consist of positive and negative ions that are strongly attracted to each other
are giant molecules in which each atom forms strong covalent bonds with all of its neighboring atoms
are formed under extreme conditions of temperature and pressure
contain orbitals or bands of delocalized electrons that belong not to single atoms but to each crystal as a whole
- 17. Multiple Choice
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?
The London (dispersion) forces increase.
The hydrogen bonding increases.
The dipole-dipole forces increase.
The chemical reactivity increases.
The number of nearest neighbors increases.
- 18. Multiple Choice
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?
Solid iodine is a network covalent solid, whereas solid bromine is a molecular solid.
The covalent bonds in I2 molecules are weaker than those in Br2 molecules.
I2 molecules have electron clouds that are more polarizable than those of Br2 molecules, thus London dispersion forces are stronger in liquid I2.
Bromine has a greater electronegativity than iodine, thus there are stronger dipole-dipole
forces in liquid bromine than in liquid iodine.
- 19. Multiple Choice
The figure above shows that in solid hydrogen fluoride there are two different distances between H atoms and F atoms. Which of the following best accounts for the two different distances?
Accommodation of the necessary bond angles in the formation of the solid
Difference in strength between covalent bonds and intermolecular attractions
Different isotopes of fluorine present in the samples
Uneven repulsions among nonbonding electron pairs
- 20. Multiple Choice
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?
Butane < 1-propanol < acetone
Butane < acetone < 1-propanol
1-propanol < acetone < butane
Acetone = butane < 1-propanol
- 21. Multiple Choice
Based on the information in the table above, which of the compounds has the highest boiling point, and why?
Butanal, because it can form intermolecular hydrogen bonds
Pentane, because it has the longest carbon chain
Pentane, because it has the most C−H bonds
Propanoic acid, because it can form intermolecular hydrogen bonds
- 22. Multiple Choice
Based on the diagram above, which of the following best helps to explain why MgO(s) is not able to conduct electricity, but MgO(l) is a good conductor of electricity?
MgO(s) does not contain free electrons, but MgO(l) contains free electrons that can flow.
MgO(s) contains no water, but MgO(l) contains water that can conduct electricity.
MgO(s) consists of separate Mg2+ ions and O2− ions, but MgO(l) contains MgO molecules that can conduct electricity.
MgO(s) consists of separate Mg2+ ions and O2− ions held in a fixed lattice, but in MgO(l) the ions are free to move and conduct electricity.
- 23. Multiple Choice
Based on the structures shown above, which of the following statements identifies the compound with the higher boiling point and provides the best explanation for the higher boiling point?
Compound 1, because it has stronger dipole-dipole forces than compound 2
Compound 1, because it forms hydrogen bonds, whereas compound 2 does not
Compound 2, because it is less polarizable and has weaker London dispersion forces than compound 1
Compound 2, because it forms hydrogen bonds, whereas compound 1 does not
- 24. Multiple Choice
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?
CS2(l), because it has stronger London dispersion forces
CS2(l), because it has weaker London dispersion forces
CCl4(l), because it has stronger London dispersion forces
CCl4(l), because it has weaker London dispersion forces
- 25. Multiple Choice
The London (dispersion) forces are weakest for which of the following gases under the same conditions of temperature and pressure?
H2
O2
Xe
F2
N2
- 26. Multiple Choice
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.)
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