Chapter 11

Give an example for each type of intermolecular force: (a) dipole-dipole interaction, (b) dipoleinduced dipole interaction, (c) ion-dipole interaction, (d) dispersion forces, (e) van der Waals forces.

Explain the term "polarizability." What kind of molecules tend to have high polarizabilities? What is the relationship between polarizability and intermolecular forces?

Explain the difference between a temporary dipole moment and the permanent dipole moment.

What physical properties should you consider in comparing the strength of intermolecular forces in solids and in liquids?

Which elements can take part in hydrogen bonding? Why is hydrogen unique in this kind of interaction?

The compounds \(\mathrm{Br}_{2}\) and ICl have the same number of electrons, yet \(\mathrm{Br}_{2}\) melts at \(-7.2^{\circ} \mathrm{C}\) and ICl melts at \(27.2^{\circ} \mathrm{C} .\) Explain.

If you lived in Alaska, which of the following natural gases would you keep in an outdoor storage tank in winter: methane \(\left(\mathrm{CH}_{4}\right),\) propane \(\left(\mathrm{C}_{3} \mathrm{H}_{8}\right),\) or butane \(\left(\mathrm{C}_{4} \mathrm{H}_{10}\right) ?\) Explain your answer.

The binary hydrogen compounds of the Group 4 A elements and their boiling points are \(\mathrm{CH}_{4},-162^{\circ} \mathrm{C} ; \mathrm{SiH}_{4},\) \(-112^{\circ} \mathrm{C} ; \mathrm{GeH}_{4},-88^{\circ} \mathrm{C} ;\) and \(\mathrm{SnH}_{4},-52^{\circ} \mathrm{C} .\) Explain the increase in boiling points from \(\mathrm{CH}_{4}\) to \(\mathrm{SnH}_{4}\).

List the types of intermolecular forces that exist between molecules (or basic units) in each of the following species: (a) benzene \(\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)\) (b) \(\mathrm{CH}_{3} \mathrm{Cl}\) (c) \(\mathrm{PF}_{3},\) (d) \(\mathrm{NaCl}\), (e) \(\mathrm{CS}_{2}\).

Which of the following species are capable of hydrogen-bonding among themselves? (a) \(\mathrm{C}_{2} \mathrm{H}_{6}\) (b) HI, (c) KF, (d) \(\mathrm{BeH}_{2}\) (e) \(\mathrm{CH}_{3} \mathrm{COOH}\)

Arrange the following in order of increasing boiling point: \(\mathrm{RbF}, \mathrm{CO}_{2}, \mathrm{CH}_{3} \mathrm{OH}, \mathrm{CH}_{3} \mathrm{Br} .\) Explain your reasoning.

Which member of each of the following pairs of substances would you expect to have a higher boiling point? (a) \(\mathrm{O}_{2}\) and \(\mathrm{Cl}_{2},\) (b) \(\mathrm{SO}_{2}\) and \(\mathrm{CO}_{2}\), (c) \(\mathrm{HF}\) and \(\mathrm{HI}\)

Which substance in each of the following pairs would you expect to have the higher boiling point? (a) Ne or \(\mathrm{Xe},\) (b) \(\mathrm{CO}_{2}\) or \(\mathrm{CS}_{2},\) (c) \(\mathrm{CH}_{4}\) or \(\mathrm{Cl}_{2},\) (d) \(\mathrm{F}_{2}\) or \(\mathrm{LiF},\) (e) \(\mathrm{NH}_{3}\) or \(\mathrm{PH}_{3}\). Explain your answer.

Explain in terms of intermolecular forces why (a) \(\mathrm{NH}_{3}\) has a higher boiling point than \(\mathrm{CH}_{4},\) and (b) \(\mathrm{KCl}\) has a higher melting point than \(\mathrm{I}_{2}\).

What kind of attractive forces must be overcome in order to (a) melt ice, (b) boil molecular bromine, (c) melt solid iodine, and (d) dissociate \(\mathrm{F}_{2}\) into F atoms?

Explain why liquids, unlike gases, are virtually incompressible.

What is surface tension? What is the relationship between intermolecular forces and surface tension? How does surface tension change with temperature?

Despite the fact that stainless steel is much denser than water, a stainless- steel razor blade can be made to float on water. Why?

Use water and mercury as examples to explain adhesion and cohesion.

A glass can be filled slightly above the rim with water. Explain why the water does not overflow.

Draw diagrams showing the capillary action of (a) water and (b) mercury in three tubes of different radii.

What is viscosity? What is the relationship between intermolecular forces and viscosity?

Why does the viscosity of a liquid decrease with increasing temperature?

Why is ice less dense than water?

Outdoor water pipes have to be drained or insulated in winter in a cold climate. Why?

Predict which of the following liquids has greater surface tension: ethanol \(\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\right)\) or dimethyl ether \(\left(\mathrm{CH}_{3} \mathrm{OCH}_{3}\right)\)

Define the following terms: crystalline solid, lattice point, unit cell, coordination number, closest packing.

Describe the geometries of the following cubic cells: simple cubic, body- centered cubic, facecentered cubic. Which of these structures would give the highest density for the same type of atoms? Which the lowest?

Classify the solid states in terms of crystal types of the elements in the third period of the periodic table. Predict the trends in their melting points and boiling points.

What is the coordination number of each sphere in (a) a simple cubic cell, (b) a body-centered cubic cell, and (c) a face- centered cubic cell? Assume the spheres are all the same.

Calculate the number of spheres that would be found within a simple cubic, a body-centered cubic, and a face-centered cubic cell. Assume that the spheres are the same.

Barium metal crystallizes in a body-centered cubic lattice (the Ba atoms are at the lattice points only). The unit cell edge length is \(502 \mathrm{pm},\) and the density of the metal is \(3.50 \mathrm{~g} / \mathrm{cm}^{3}\). Using this information, calculate Avogadro's number. [Hint: First calculate the volume (in \(\mathrm{cm}^{3}\) ) occupied by 1 mole of Ba atoms in the unit cells. Next calculate the volume (in \(\mathrm{cm}^{3}\) ) occupied by one Ba atom in the unit cell. Assume that \(68 \%\) of the unit cell is occupied by Ba atoms.

Vanadium crystallizes in a body-centered cubic lattice (the \(\mathrm{V}\) atoms occupy only the lattice points). How many \(\mathrm{V}\) atoms are present in a unit cell?

Crystalline silicon has a cubic structure. The unit cell edge length is \(543 \mathrm{pm}\). The density of the solid is \(2.33 \mathrm{~g} / \mathrm{cm}^{3}\). Calculate the number of Si atoms in one unit cell.

A face-centered cubic cell contains \(8 \mathrm{X}\) atoms at the corners of the cell and 6 Y atoms at the faces. What is the empirical formula of the solid?

Write the Bragg equation. Define every term and describe how this equation can be used to measure interatomic distances.

When X rays of wavelength \(0.090 \mathrm{nm}\) are diffracted by a metallic crystal, the angle of first-order diffraction \((n=1)\) is measured to be \(15.2^{\circ} .\) What is the distance (in pm) between the layers of atoms responsible for the diffraction?

The distance between layers in a \(\mathrm{NaCl}\) crystal is \(282 \mathrm{pm} .\) X rays are diffracted from these layers at an angle of \(23.0^{\circ} .\) Assuming that \(n=1,\) calculate the wavelength of the X rays in \(\mathrm{nm}\).

Describe and give examples of the following types of crystals: (a) ionic crystals, (b) covalent crystals, (c) molecular crystals, (d) metallic crystals.

Why are metals good conductors of heat and electricity? Why does the ability of a metal to conduct electricity decrease with increasing temperature?

A solid is hard, brittle, and electrically nonconducting. Its melt (the liquid form of the substance) and an aqueous solution containing the substance conduct electricity. Classify the solid.

A solid is soft and has a low melting point (below \(100^{\circ} \mathrm{C}\) ). The solid, its melt, and an aqueous solution containing the substance are all nonconductors of electricity. Classify the solid.

A solid is very hard and has a high melting point. Neither the solid nor its melt conducts electricity. Classify the solid.

Which of the following are molecular solids and which are covalent solids? \(\mathrm{Se}_{8}, \mathrm{HBr}, \mathrm{Si}, \mathrm{CO}_{2}, \mathrm{C}, \mathrm{P}_{4} \mathrm{O}_{6}, \mathrm{SiH}_{4}\)

Classify the solid state of the following substances as ionic crystals, covalent crystals, molecular crystals, or metallic crystals: (a) \(\mathrm{CO}_{2},\) (b) \(\mathrm{B}_{12},\) (c) \(\mathrm{S}_{8}\), (d) \(\mathrm{KBr}\) (e) \(\mathrm{Mg}\), (f) \(\mathrm{SiO}_{2},(\mathrm{~g}) \mathrm{LiCl}\) (h) Cr.

Explain why diamond is harder than graphite. Why is graphite an electrical conductor but diamond is not?

What is an amorphous solid? How does it differ from crystalline solid?

Define glass. What is the chief component of glass? Name three types of glass.

What is a phase change? Name all possible changes that can occur among the vapor, liquid, and solid phases of a substance.

What is the equilibrium vapor pressure of a liquid? How is it measured and how does it change with temperature?