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chemistry a molecular approach

Questions and Answers of Chemistry A Molecular Approach

Describe the difference between vitreous silica and soda-lime glass. What are some advantages and disadvantages of each of these types of glass?
In band theory of bonding for solids, what is a band? What is the difference between the valence band and the conduction band?
In band theory of bonding for solids, what is a band gap? How does the band gap differ in metals, semiconductors, and insulators?
Explain how doping can increase the conductivity of a semiconductor.What is the difference between an n-type semiconductor and a p-type semiconductor?
What is the trend in the size of the band gap as you move down the column of the group 4A elements?
What is a polymer? What is the difference between a polymer and a copolymer?
How do an addition polymer and a condensation polymer differ from each other?
An X-ray beam with λ = 154 pm incident on the surface of a crystal produced a maximum reflection at an angle of θ = 28.3°.Assuming n = 1, calculate the separation between layers of atoms in the
Determine the number of atoms per unit cell for each metal. (a) Polonium (c) Nickel (b) Tungsten
An X-ray beam of unknown wavelength is diffracted from a NaCl surface. If the interplanar distance in the crystal is 286 pm, and the angle of maximum reflection is found to be 7.23°, what is the
Determine the coordination number for each structure. (a) Gold (b) Ruthenium
Calculate the packing efficiency of the body-centered cubic unit cell. Show your work.
Calculate the packing efficiency of the face-centered cubic unit cell. Show your work.
Platinum crystallizes with the face-centered cubic unit cell. The radius of a platinum atom is 139 pm. Calculate the edge length of the unit cell and the density of platinum in g/cm3.
Molybdenum crystallizes with the body-centered unit cell. The radius of a molybdenum atom is 136 pm. Calculate the edge length of the unit cell and the density of molybdenum.
Rhodium has a density of 12.41 g/cm3 and crystallizes with the face-centered cubic unit cell. Calculate the radius of a rhodium atom.
Barium has a density of 3.59 g/cm3 and crystallizes with the body-centered cubic unit cell. Calculate the radius of a barium atom.
Polonium crystallizes with a simple cubic structure. It has a density of 9.3 g/cm3, a radius of 167 pm, and a molar mass of 209 g/mol. Use these data to calculate Avogadro’s number (the number of
Palladium crystallizes with a face-centered cubic structure. It has a density of 12.0 g/cm3, a radius of 138 pm, and a molar mass of 106.42 g/mol. Use these data to calculate Avogadro’s number.
Identify each solid as molecular, ionic, or atomic. a. Ar(s) C. K₂O(s) b. H₂O (s) d. Fe(s)
Identify each solid as molecular, ionic, or atomic. a. CaCl₂(s) C. Ni(s) b. CO₂ (s) d. 1₂(s)
Which solid has the highest melting point? Why?Ar(s), CCl4(s), LiCl(s), CH3OH(s)
Which solid has the highest melting point? Why?C(s, diamond), Kr(s), NaCl(s), H2O(s)
Which solid in each pair has the higher melting point and why? a. C. TiO₂ (s) or HOOH(s) Kr(s) or Xe(s) b. CCl4(s) or SiCl4(s) d. NaCl(s) or CaO(s)
Which solid in each pair has the higher melting point and why? a. Fe(s) or CCl4(s) C. Ti(s) or Ne(s) b. KCI(s) or HCl(s) d. H₂O(s) or H₂S(s)
An oxide of titanium crystallizes with the unit cell shown here (titanium = gray; oxygen = red). What is the formula of the oxide?
An oxide of rhenium crystallizes with the unit cell shown here (rhenium = gray; oxygen = red). What is the formula of the oxide?
The unit cells for cesium chloride and barium chloride are shown here. Show that the ratio of cations to anions in each unit cell corresponds to the ratio of cations to anions in the formula of each
The unit cells for lithium oxide and silver iodide are shown here. Show that the ratio of cations to anions in each unit cell corresponds to the ratio of cations to anions in the formula of each
Identify the structure of each of the two unit cells shown in Problem 47 as the rock salt structure, zinc blende structure, fluorite structure, antifluorite structure, or none of these.Problem 47The
Identify the structure of each of the two unit cells shown in Problem 48 as the rock salt structure, zinc blende structure, fluorite structure, antifluorite structure, or none of these.Problem 48The
Consider the rock salt structure in Figure 13.15. What type of structure would result if all the anions were somehow removed, leaving only cations? Sodium chloride (NaCl) CI™ Na+ A FIGURE 13.15
Consider the zinc blende structure in Figure 13.16. What type of structure would result if the remaining tetrahedral sites in the unit cell were also filled with cations? Zinc blende
Classify each of the following as a component of a silicate ceramic, an oxide ceramic, or a nonoxide ceramic.a. B4Cb. Mg2SiO4c. MoSi2
Classify each of the following as a component of a silicate ceramic, an oxide ceramic, or a nonoxide ceramic.a. TiB2 b. ZrO2 c. NaAlSi3O8
What are the name and formula of the compound commonly used in the manufacture of glass to reduce its tendency to crack or shatter under thermal shock?
What are the name and formula of the compound commonly used in the manufacture of glass to increase the index of refraction?
One of the key components in the manufacture of Portland cement is Ca3SiO5, a compound that is obtained by firing the reactants in a kiln at 1400–1500 °C. Assign an oxidation state to each element
Replacement of aluminum ions in kaolinite with magnesium ions yields a compound with the formula Mg3Si2O5(OH)4.Assign an oxidation state to each element in this compound.
Which solid would you expect to have little or no band gap?a. Zn(s)b. Si(s)c. As(s)
Which solid would you expect to have the largest band gap?a. As(s)b. Sb(s)c. Bi(s)
How many molecular orbitals are present in the conduction band of a lithium crystal with a mass of 11.2 g?
How many molecular orbitals are present in the valence band of a sodium crystal with a mass of 5.45 g?
A substance has a band gap of 6.9 eV at 273 K. Is this substance best classified as an insulator, a semiconductor, or a metal?
A substance has a band gap of 0.85 eV at 273 K. Is this substance best classified as an insulator, a semiconductor, or a metal?
Indicate if each solid forms an n-type or a p-type semiconductor.a. Germanium doped with galliumb. Silicon doped with arsenic
Indicate if each solid forms an n-type or a p-type semiconductor.a. Silicon doped with galliumb. Germanium doped with antimony
Does a photon of red light with a frequency of 4.29 * 1014 Hz have sufficient energy to promote an electron from the valence band to the conduction band in a sample of silicon (the band gap in
Teflon is an addition polymer formed from the monomer shown here. Draw the structure of the polymer. F F C= FC F
Which wavelength of light (in nm) is emitted if an electron moves from the conduction band to the valence band in a sample of diamond (diamond has a band gap of 5.5 eV)?
Saran, the polymer used to make Saran Wrap, is an addition polymer formed from two monomers—vinylidene chloride and vinyl chloride. Draw the structure of the polymer. H C=C Cl H Cl Vinylidene
One kind of polyester is a condensation copolymer formed from terephthalic acid and ethylene glycol. Draw the structure of the dimer. HO Terephthalic acid OH HD-CH₂-CH₂-OH Ethylene glycol
Nomex, a condensation copolymer used by firefighters because of its flame-resistant properties, forms from isophthalic acid and m-aminoaniline. Draw the structure of the dimer. HO Isophthalic
Polyacetylene is an addition polymer with the structure shown here. Draw the structure of the monomer. H [₁] C. C H
Polyacrylonitrile (PAN) is an addition polymer with the structure shown here. Draw the structure of the monomer. Η \/ H Η Η Η C -UEZ C N In
The polycarbonate Lexan is a condensation polymer and has the structure shown here:Assuming this polymer was formed from the monomer shown here plus another monomer, provide a possible structure for
Consider the condensation polymer with the structure shown here:Assuming this polymer was formed from the monomer shown here plus another monomer, provide the structure of the other monomer that
Copper iodide crystallizes in the zinc blende structure. The separation between nearest-neighbor cations and anions is approximately 311 pm, and the melting point is 606 °C. Potassium chloride, by
Consider the face-centered cubic structure shown here:a. What is the length of the line (labeled c) that runs diagonally across one of the faces of the cube in terms of r (the atomic radius)?b. Use
Consider the body-centered cubic structure shown here:a. What is the length of the line (labeled c) that runs from one corner of the cube diagonally through the center of the cube to the other corner
The volume of a unit cell of diamond is 0.0454 nm3, and the density of diamond is 3.52 g/cm3. Find the number of carbon atoms in a unit cell of diamond.
An unknown metal is found to have a density of 7.8748 g/cm3 and to crystallize in a body-centered cubic lattice. The edge of the unit cell is 0.28664 nm. Calculate the atomic mass of the metal.
The density of an unknown metal is 12.3 g/cm3, and its atomic radius is 0.134 nm. It has a face-centered cubic lattice. Find the atomic mass of this metal.
When spheres of radius r are packed in a body-centered cubic arrangement, they occupy 68.0% of the available volume. Use the fraction of occupied volume to calculate the value of a, the length of the
Potassium chloride crystallizes in the rock salt structure. Estimate the density of potassium chloride using the ionic radii provided in Chapter 9.
Calculate the fraction of empty space in cubic closest packing to five significant figures.
A tetrahedral site in a closest-packed lattice is formed by four spheres at the corners of a regular tetrahedron. This is equivalent to placing the spheres at alternate corners of a cube. In such a
X-ray diffractometers often use metals that have had their core electrons excited as a source of X-rays. Consider the 2p → 1s transition for copper, which is called the Ka transition. Calculate the
Why is it necessary to use the Ka transition (2p → 1s) in copper (see Problem 88) to generate X-rays? Why not use, for example, the 4s → 3p transition?Problem 88X-ray diffractometers often use
In certain cases where X-ray diffraction is unsuitable for determining the structure of a crystal, neutron diffraction can be used.Instead of X-rays, a beam of neutrons is used to analyze the
How much heat (in kJ) is evolved in converting 1.00 mol of steam at 145 °C to ice at -50 °C? The heat capacity of steam is 2.01 J/g · °C, and that of ice is 2.09 J/g · °C.
Consider the phase diagram shown here. Identify the states present at points a through g. Pressure (not to scale) Pc- a. e 0Q g b G 14 •Pl I Ic Temperature (not to scale)
Consider the phase diagram for iodine shown here.a. What is the normal boiling point for iodine?b. What is the melting point for iodine at 1 atm?c. What state is present at room temperature and
Argon has a normal boiling point of 87.2 K and a melting point (at 1 atm) of 84.1 K. Its critical temperature is 150.8 K, and its critical pressure is 48.3 atm. It has a triple point at 83.7 K and
Convert between energy units.a. 231 cal to kJb. 132 * 104 kJ to kcalc. 4.99 * 103 kJ to kWhd. 2.88 * 104 J to Cal
Suppose that a person eats 2387 Calories per day. Convert this amount of energy into each unit.a. Jb. kJc. kWh
A particular frost-free refrigerator uses about 745 kWh of electrical energy per year. Express this amount of energy in each unit.a. Jb. kJc. Cal
Which statement is true of the internal energy of a system and its surroundings during an energy exchange with a negative ΔEsys?a. The internal energy of the system increases and the internal energy
During an energy exchange, a chemical system absorbs energy from its surroundings. What is the sign of ΔEsys for this process? Explain.
Identify each energy exchange as primarily heat or work and determine whether the sign of ΔE is positive or negative for the system.a. Sweat evaporates from skin, cooling the skin. (The evaporating
Identify each energy exchange as primarily heat or work and determine whether the sign of ΔE is positive or negative for the system.a. A rolling billiard ball collides with another billiard ball.
A system releases 622 kJ of heat and does 105 kJ of work on the surroundings.What is the change in internal energy of the system?
A system absorbs 196 kJ of heat, and the surroundings do 117 kJ of work on the system. What is the change in internal energy of the system?
The gas in a piston (defined as the system) warms and absorbs 655 J of heat. The expansion performs 344 J of work on the surroundings. What is the change in internal energy for the system?
The air in an inflated balloon (defined as the system) warms over a toaster and absorbs 115 J of heat. As it expands, it does 77 kJ of work. What is the change in internal energy for the system?
We pack two identical coolers for a picnic, placing 24 12-ounce soft drinks and five pounds of ice in each. However, the drinks that we put into cooler A were refrigerated for several hours before
A kilogram of aluminum metal and a kilogram of water are each warmed to 75 °C and placed in two identical insulated containers.One hour later, the two containers are opened, and the temperature of
How much heat is required to warm 1.50 L of water from 25.0 °C to 100.0 °C?
How much heat is required to warm 1.50 kg of sand from 25.0 °C to 100.0 °C?
The average human lung expands by about 0.50 L during each breath. If this expansion occurs against an external pressure of 1.0 atm, how much work (in J) is done during the expansion?
The air within a piston equipped with a cylinder absorbs 565 J of heat and expands from an initial volume of 0.10 L to a final volume of 0.85 L against an external pressure of 1.0 atm. What is the
A gas is compressed from an initial volume of 5.55 L to a final volume of 1.22 L by an external pressure of 1.00 atm. During the compression the gas releases 124 J of heat. What is the change in
When 1 mol of a fuel burns at constant pressure, it produces 3452 kJ of heat and does 11 kJ of work. What are ΔE and ΔH for the combustion of the fuel?
The change in internal energy for the combustion of 1.0 mol of octane at a pressure of 1.0 atm is 5084.3 kJ. If the change in enthalpy is 5074.1 kJ, how much work is done during the combustion?
Determine whether each process is exothermic or endothermic and indicate the sign of ΔH.a. Natural gas burning on a stoveb. Isopropyl alcohol evaporating from skinc. Water condensing from steam
Consider the thermochemical equation for the combustion of acetone (C3H6O), the main ingredient in nail polish remover:If a bottle of nail polish remover contains 177 mL of acetone, how much heat is
Determine whether each process is exothermic or endothermic and indicate the sign of ΔH.a. Dry ice evaporatingb. A sparkler burningc. The reaction that occurs in a chemical cold pack used to ice
What mass of natural gas (CH4) must burn to emit 267 kJ of heat? CH4(g) + 2 Oz(g) — COz(g) + 2H,O(g) AH = -802.3 kJ xxn
Nitromethane (CH3NO2) burns in air to produce significant amounts of heat.How much heat is produced by the complete reaction of 5.56 kg of nitromethane? 2 CH3NO2(I) + 3/2O2(g) 2 CO2(g) + 3 H2O(1) +
Titanium reacts with iodine to form titanium(III) iodide, emitting heat.Determine the masses of titanium and iodine that react if 1.55 * 103 kJ of heat is emitted by the reaction. 2 Ti(s) + 3

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