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All Textbook Solutions for Chemistry for Engineering Students

• list the number of orbitals of each type (1s, 3p, etc) in an atom.• sketch the shapes of s and p orbitals and recognize orbitals by their shapes.• rank various orbitals in terms of size and energy.17CO 18CO 19CO 20CO 6.1PAE 6.2 Unlike XRF, AAS cannot be used for nondestructive testing. Explain why not.6.3PAE 6.4PAE 6.5PAE 6.6PAE 6.7 Arrange the following regions of the electromagnetic spectrum in order of increasing frequency: IR, UV, radio wave, visible.6.8 Calculate the wavelength in meters, of radiation of the following frequencies. (a) 5.001015s1 (b) 2.111014s1 (c) 5.441012s1 6.9 If a string of decorative lights includes bulbs with wave-lengths of 480, 580, and 700 mm, what are the frequencies of the lights? Use Figure 6.6 to determine which colors are in the set.6.10 Define the term refraction.6.11 Define the term photon.6.12 Find the energy of a photon with each of the following frequencies (see Table 1.2 if needed). (a) 15.3 THz, (b) 1.7 EHz, (c) 6.221010 Hz 6.13 Place these types of radiation in order of increasing energy per photon. (a) green light from a mercury lamp, (b) X-rays from a dental X-ray, (c) microwave oven, (d) an FM music station broadcasting at 89.1 MHz 6.14 For photon with the following energies, calculate the wavelength and identify the region of the spectrum they are from. (a) 3.51020 J, (b) 8.71026 J, (c) 7.11017 J, (d) 5.51027 J 6.15PAE 6.16 Various optical disk drives rely on laser operating at different wavelengths, with shorter wavelengths allowing a higher density of data storage. For each of the following drive types, find the energy of a single photon at the specified wavelength. (a) CD, =780nm , (b) DVD, =650nm , (c) Blu-ray disc, =405nm 6.17 The laser in most supermarket barcode scanners operates at a wavelength of 632.8 nm. What is the energy of a single photon emitted by such a laser? What is the energy of one mole of these photons?6.18 Assume that a microwave oven operates at a frequency of 1.001011s1 . (a) What is the wavelength of this radiation in meters? (b) What is the energy in joules per photon? (c) What is the energy per mole of photons?6.19 Fill in the blanks below to complete a description of the photoelectric effect experiment. (You should be able to do this with just one or two words in each blank.) A beam of_________ strikes __________ causing to be emitted.6.20 When light with a wavelength of 58.5 nm strikes the surface of tin metal, electrons are ejected with a maximum kinetic energy of 2.691018 J. What is the binding energy of these electrons to the metal?6.21 The electron binding energy fur copper metal is 7.181019J . Find the longest wavelength of light that could eject electrons from copper in a photoelectric effect experiment.6.22PAE 6.23 Describe how the Bohr model of the atom accounts for the spectrum of the hydrogen atom.6.24 According to the Bohr model of the atom, what happens when an atom absorbs energy?6.25 Define the term ground state.6.26 The figure below depicts the first four energy levels in a hydrogen atom. The three transitions shown as arrows emit ultraviolet light and occur at wavelengths of 121.566 nm, 102.583nm.and 97.524 nm, respectively. Find the frequency of light that would be emitted in a transition from the state labeled as n = 4 to the state labeled as n = 3.6.27 Refer w the data and energy-Ievel diagram shown in Problem 6.26, and find the wavelength of light that would be emitted when a hydrogen atom undergoes the transition from the state labeled as n = 4 to the state labeled as n = 2. Express your answer in nm.6.28 A neon atom cmi light at many wavelengths, two of which are at 616.4 and 638.3 nm. Both of these transitions are to the same final state. (a) What is the energy difference between the two states for each transition? (b) If a transition between the two higher energy states could be observed, what would be the frequency of the light?6.29 A mercury atom emits light at many wavelengths, two of which are at 435.8 and 546.1 nm. Both of these transitions are to the same final state. (a) What is the energy difference between the two states for each transition? (b) lf a transition between the two higher energy states could be observed, what would be the frequency of the light?6.30 How did the observation of electron diffraction affect the development of the quantum mechanical model of the atom?6.31 Why do we use a wave function to describe electrons?6.32 What are the mathematical origins of quantum numbers?6.33PAE 6.34 Which of the following represent valid sets of quantum numbers? For a set that is invalid, explain briefly why it is not correct. (a) n = 3, l = 3, ml= 0, (b) n = 2, l = 1, ml=0, (c) n = 6, l = 5, ml= —1, (d) n = 4, l = 3, ml= —4 6.35 A particular orbital has n = 4 and l = 2. What type of orbital must this be? (a) 3p, (b) 4p, (c) 5d, or (d) 4d 6.36 Why are there no 2d orbitals?6.34 What is the maximum number of electrons in an atom that can have the following quantum numbers? (a) n = 2; (b) n = 3 and l = 1; (c) n = 3, l = 1, ml= 0; (d) n = 3, l = 1, ml= —1 and ml= —1/2.6.38 How many orbitals correspond to each of the following designations? (a) 3p, (b) 4p, (c) 4px, (d) 6d, (e) 5d, (f) 5f, (g) n = 5, (h) 7s 6.39PAE 6.40 Referring to Figure 6.15, draw a 4p orbitals, showing all of its nodes.6.41 Consider a 3d orbital. (a) What are the allowed values for the n and l quantum numbers for a 3d orbital? (b) What are the allowed values for the mlquantum number for a 3d orbital? (c) What is the maximum number of 3d orbitals that could be present in any one atom? (d) What is the maximum number of electrons that could occupy a single 3d orbital?6.42PAE 6.43 Define the term spin paired.6.44 On what does the Pauli exclusion principle place a limit?6.45PAE 6.46PAE 6.47 Depict two ways to place electrons in the 2p orbitals for a nitrogen atom. Which depiction is correct according to Hund’s rule?6.48 Write the ground state electron configuration for (a) B, (b) Ba, (c) Be, (d) Bi, (e) Br.6.49 Which of these electron configurations are for atoms in the ground state? In excited states? Which are impossible? (a) 1s22s1, (b) 1s22s22p3, (c) [Ne] 3s23p34s1, (d) [Ne] 3s23p64s23d2, (e) [Ne] 3s23p64f 4, (f) 1s22s22p43s2 6.50 From the list of atoms and ions given, identify any pairs that have the same electron configurations and write that configuration: Na+, S2, Ne, Ca2+, Fe2+, Kr, I.6.51PAE 6.52PAE 6.53PAE 6.54PAE 6.55 Explain why the s block of the periodic table contains two columns, the p block contains six columns, and the d block contains ten columns.6.56PAE 6.57PAE 6.58PAE 6.59PAE 6.60 Use the electron configurations of the alkali metals and your knowledge of orbitals and quantum numbers to explain the trend in atomic size of alkali metal atoms.6.61 Using only a periodic table as a guide, arrange each of the following series of atoms in order of increasing size. (a) Na, Be, Li, (b) P, N, F, (c) I, O, Sn 6.62 Define the term ionization energy. Distinguish between the first ionization energy and the second ionization energy.6.63 At which ionization for chlorine would you expect the first large jump in ionization energy? Would this be the only large jump in energy if you continued to ionize the chlorine?6.64 Arrange the following atoms in order of increasing ionization energy: Li, K, C, and N.6.65PAE 6.66 Which element would you expect to have the largest second ionization energy, Na, C, or F? Why?6.67PAE 6.68 Indicate which species in each pair has the more favorable (more negative) electron affinity. Explain your answers. (a) Cl or S, (b) S or P, (c) Br or As 6.69 Compare the elements Na, B, Al, and C with regard to the following properties. (a) Which has the largest atomic radius? (b) Which has the most negative electron affinity? (c) Place the elements in order of increasing ionization energy.6.70 Rank the following in order of decreasing ionization energy: Cl , F, Ne+ , S, S .6.71 Several excited states of the neon atom are important in the operation of a helium-neon laser. In these excited states, one electron of the neon atom is promoted from the 2p level to a higher energy orbital. An excited neon atom with a 1s22s22p55s1 electron configuration can emit a photon with a wavelength of 3391 nm as it makes a transition to a lower energy state with a 1s22s22p54p1 electron configuration. Other transitions are also possible. If an excited neon atom with a 1s22s22p53p1 electron configuration makes a transition to a lower energy state with a 1s22s22p53p1 electron configuration, it emits a photon with a wavelength of 632.8 nm. Find the wavelength of the photon that would be emitted in a transition from the 1s22s22p54p1 electron configuration to the 1s22s22p53p1 electron configuration. (It should help if you start by drawing an energy-level diagram.)6.72 LED bulbs offer a fairly new lighting alternative, and are becoming increasingly popular in home lighting. These bulbs combine excellent energy efficiency with the “warm” light and dimming ability of incandescent lights. Although LED bulbs are expensive, manufacturers claim that subsequent savings will more than offset the initial costs. Analyze the relative cost of incandescent versus LED lighting, assuming that the information in the table below is accurate. Are industry claims of cost savings justified? LED Incandescent Initial cost $4.00 $0.75 Electricity usage 8 watts 60 watts Electricity cost $0.04/kwh $0.04/kwh Lifetime 25,000 hours 1,500 hours 6.73 How much energy could be saved each year by replacing incandescent bulbs with LED bulbs? Assume that six 60-watt lamps are lit an average of three hours a night and they are each replaced with 8-watt LED bulbs. (See Problem 6.72.)6.74PAE 6.75PAE 6.76PAE 6.77PAE 6.78PAE 6.79 How does the charge of electrons provide some rationale for Hund’s rule?6.80 Describe how valence electron configurations account for some of the similarities in chemical properties among elements in a group.6.81 Why is there no element to the immediate right of magnesium in the periodic table?6.82 A particular element has the following values for its first four ionization energies: 900, 1760, 14, 850, and 21,000 kJ/mol. Without consulting a list of ionization energy values, determine what group in the periodic table this element belongs in.6.83 The graph below shows the first three ionization energies for sodium, magnesium, and aluminum. Without consulting a list of values, determine which line in the graph corresponds to each element. Number of electrons removed 6.84 Which graph correctly depicts the first ionization energy of three elements in groups 14 (dashed line) and 17 (solid line)? Explain the reasoning you used to make your choice.6.85 The visible lines in the hydrogen atom emission spectrum arise from transitions with a final state with n = 2. In what spectral region should we expect to find transitions that have a final state of n = 1 ? Explain your reasoning using an energy level diagram similar to the one in Problem 6.26.6.86 An excited He+ ion returns to the ground state by emitting a series of three photons, with wavelengths of 26 nm, 469 nm, and 1014 nm. The process is represented in the energy level diagram below. Which arrow (A, B, or C) in the diagram represents the 1014-nm light?6.87PAE 6.88PAE 6.89PAE 6.90PAE 6.91 What is the only noble gas that does not have an ns2np6 electron configuration? How can it be a noble gas without this electron configuration?6.92 The photoelectric effect can he used to measure the value of Planck's constant. Suppose that a photoelectric effect experiment was carried out using light with v=7.501014s1 and ejected electrons were detected with a kinetic energy of 2.501011 J. The experiment was then repeated using light with v=1.001015s1 and the same metal target, and electrons were ejected with kinetic energy of 5.001011 J. Use these data to find a value for Planck’s constant. HINTS: These data are fictional and will give a result that is quite different from the real value of Planck's constant. Be sure that you do not use the real value of Planck's constant in any calculations here. It may help to start by thinking about how you would calculate the metal's binding energy if you already knew Planck's constant.6.93 A mercury atom is initially in its lowest possible (or ground state) energy level. The atom absorbs a photon with a wavelength of 185 nm and then emits a photon with a frequency of 4.9241014HZ . At the end of this series of transitions, the atom will still be in an energy level above the ground state. Draw an energy-level diagram for this process and find the energy of this resulting excited state, assuming that we assign a value of E = 0 to the ground state. (This choice of E = 0 is not the usual convention, but it will simplify the calculations you need to do here.)6.94PAE 6.95 A metallic sample is known to be barium, cesium, lithium, or silver. The electron binding energies for these metals are listed in the following table. Metal Electron Binding Energy(J) Barium 4.301019 Cesium 3.111019 Lithium 3.941019 Silver 7.591019 One way to identify the element might be through a photoelectric effect experiment. The experiment was performed three times, each time using a different laser as the light sources. The results are summarized below. (The Kinetic energy of the ejected photoelectrons was not measured.) Laser Wavelength Photoelectrons Seen? 532 nm No 488 nm Yes 308 nm Yes Based on this information, what conclusions can be drawn as to the identity of the metal?6.96 When a helium atom absorbs light at 58.44 nm, an electron is promoted from the 1s orbital to a 2p orbital. Given that the ionization energy of (ground state) helium is 2372 kJ/ mol, find the longest wavelength of light that could eject an electron from the excited state helium atom.6.97 Arrange the members of each of the following sets of cations in order of increasing ionic radii. (a) K+,Ca2+,Ga3+, (b) Ca2+,Be2+,Mg2+, (c) Al3+,Sr2+,Rb+,Na+, (d) K+,Ca2+,Rb+6.98 Arrange the following sets of anions in order of increasing ionic radii. (a) Cl,S2,P3, (b) O2,S2,Se2, (c) N3,S2,Br,P3, (d) Cl,Br,I 6.99 The photoelectric effect can he used in engineering designs for practical applications. For example, infrared goggles used in night-vision applications have materials that give an electrical signal with exposure to the relatively long wavelength IR light. If the energy needed for signal generation is 3.51020J , what is the wavelength and frequency of light that barely can be detected?6.100 Some spacecraft use ion propulsion engines. These engines create thrust by ionizing atoms and then accelerating and expelling them. According to Newton's laws, this leads to thrust in the opposite direction. Minimizing mass is always important for space applications. Discuss what periodic trends you would need to consider for choosing a material to ionize for engineering designs with this application.6.101 Laser welding is a technique in which a tightly focused laser beam is used to deposit enough energy to weld metal parts together. Because the entire process can be automated, it is commonly used in many large-scale industries, including the manufacture of automobiles. In order to achieve the desired weld quality, the steel parts being joined must absorb energy at a rate of about 104 W/mm2. (Recall that 1 W = 1 J/s.) A particular laser welding system employs a Nd:YAG laser operating at a wavelength of 1.06m ; at this wavelength steel will absorb about 80% of the incident photons. If the laser beam is focused to illuminate a circular spot with a diameter of 0.02 inch, what is the minimum power (in watts) that the laser must emit to reach the 104 W/mm2 threshold? How many photons per second does this correspond to? (For simplicity, assume that the energy from the laser does not penetrate into the metal to any significant depth.)6.102PAE 6.103 Atomic absorption spectroscopy is based on the atomic spectra of the elements being studied. It can be used to determine the impurities in a metal sample. If an element is present, light at the appropriate wavelength is absorbed. You are working with a metal stamping company and the rolled steel you use to form panels for automobile doors is failing at an alarming rate. There is some chance that the problem is unacceptably high levels of manganese in the steel. Given that the atomic spectrum of manganese has three lines near 403 nm, how could you use a spectrometer to determine the amount of manganese in the steel?6.104 The red color in fireworks is the result of having strontium-containing salts in the fireworks bomb. Similarly, the green/blue colors sometimes seen in fireworks arise from copper salts. Based on your understanding of atomic spectra and the colors in fireworks, describe which atom, copper or strontium, has more widely separated energy levels.6.105 When we say that the existence of atomic spectra tells us that atoms have specific energy levels, are we using deductive or inductive reasoning?6.106 When Bohr devised his model for the atom, was he using deductive or inductive reasoning? Explain your answer.6.107PAE List some factors influencing the biocompatibility of materials and explain how those factors are related to chemical bonding.• use electron configurations to explain why metals tend to form cations whereas nonmetals tend to form anions.• describe die energy changes in the formation of an ionic bond.• define electronegativity and state how electronegativity varies with position in the periodic table.• identify or predict polar, nonpolar, and ionic bonds by comparing electronegativities.• write Lewis electron structures for molecules or ions.• describe chemical bonding using a model based on the overlap of atomic orbitals and recognize sonic of the limitations of this simple model.• explain how hybridization reconciles observed molecular shapes with the orbital overlap model.• predict the geometry of a molecule from its, Lewis structure.• use models (real or software) to help visualize common molecular shapes.• explain the formation of multiple bonds in terms of the overlap of a combination of hybridized and unhybridized atomic orbitals.• identify sigma and pi bonds in a molecule and explain the difference between them.Define the term biocompatibility.List some properties associated with biomaterials used for joint replacements.7.3PAE 7.4PAE 7.5PAE 7.6PAE Why is the ion not found in nature?Why do nonmetals tend to form anions rather than cations?7.9PAE 7.10 Arrange the members of each of the following sets of cations in order of increasing ionic radii. (a) K+,Ca2+,Ga3+, (b) Ca2+,Be2+,Ba2+,Mg2+, (c) Al3+,Sr2+,Rb+,K+, (d) k+,Ca2+,Rb+7.11 Arrange the following sets of anions in order of increasing ionic radii. (a) Cl,P3,S2, (b) S2,O2,Se2, (c) Br,N3,S2, (d) Br,Cl,I 7.12 Which pair will form a compound with the larger lattice energy: Na and F or Mg and F? Why?7.13 Figure 7-2 depicts the interactions of an ion with its first nearest neighbors, second nearest neighbors, and third nearest neighbors in a lattice, (a) Would the interactions with the fourth nearest neighbors be attractive or repulsive? (b) Based on Coulomb's law, how would the relative sizes of the terms compare if the potential energy were expressed as V=V1st+V2nd+V3rd+V4th ?7.14 Describe the difference between a covalent bond and an ionic bond.7.15 Covalently bonded compounds tend to have much lower melting and boiling points than ionic compounds. How can the differences between ionic and covalent bonding explain this observation?7.16PAE 7.17 Coulombic forces are often used to explain ionic bonding. Are coulombic forces involved in covalent bonding as well? Explain.7.18 In terms of the strengths of the covalent bonds involved, why do combustion reactions release energy?7.19 If the formation of chemical bonds always releases energy, why don't all elements form dozens of bonds to each atom?7.20 Draw the Lewis dot symbol for each of the following atoms, (a) boron, (b) fluorine, (c) selenium, (d) indium 7.21 Theoretical models for the structure of atomic nuclei predict the existence of superheavy elements that have not yet been discovered and suggest that such elements might be fairly stable if they could be produced. So researchers are currently trying to synthesize these superheavy elements to test these theories. Element 117 has been synthesized and named Tennessine (Ts). What would the Lewis dot symbol be for this new element?7.22 Use Lewis dot symbols to explain why chlorine bonds with only one hydrogen atom.7.23 Define the term lone pair.7.24 How many electrons are shared between two atoms in (a) a single covalent bond, (b) a double covalent bond, and (c) a triple covalent bond?7.25 How does the bond energy of a double bond compare to that of two single bonds between the same elements? How does this relationship explain the types of reactions that compounds with double bonds undergo?7.26 How is electronegativity defined?7.27 Distinguish between electron affinity and electronegativity.7.28 Certain elements in the periodic table shown in Figure 7.7 had no electronegativity value defined. Based on the definition of electronegativity and the identity of these elements, hypothesize as to why they have no electronegativity value.7.29 When two atoms with different electronegativities form a covalent bond, what does the electron distribution in the bond look like?7.30 The bond in HF is said to be polar, with the hydrogen carrying a partial positive charge. For this to be true, the hydrogen atom must have less than one electron around it. Yet the Lewis dot structure of HF attributes two electrons to hydrogen. Draw a picture of the electron density distribution for HF and use it to describe how the hydrogen atom can carry a partial positive charge. How can these two models of the HF bond (the electron density and the Lewis structure) seem so different and yet describe the same thing?7.31 Why is a bond between two atoms with different electronegativities called a polar bond?7.32PAE 7.33 In each group of three bonds, which bond is likely to be the most polar? Which will be the least polar? (a) CH, OH, SH, (b) CCl, ClCl, HCl, (c) FF, OF, CF. (d) NH, NO, NCl 7.34PAE 7.35 Which one of the following contains botb ionic and covalent bonds? (a) BaCO3 , (b) MgCl2 , (c) BaO , (d) H2S , (e) So42 7.36PAE 7.37 Draw the Lewis structure for each of the following molecules. (a) CO , (b) H2S , (c) SF6 , (d) NCl3 7.38 Draw a Lewis structure for each of the following molecules or ions. (a) CS2 , (b) BF4 , (c) HNO2 , (where the bonding is in the order HONO), (d) OSCl2 (where S is the central atom)7.39PAE 7.40 Why is it impossible for hydrogen to be the central atom in the Lewis structure of a polyatomic molecule?7.41PAE 7.42 Draw resonance structure for (a) (b) and (c)7.43PAE 7.44PAE 7.45PAE 7.46 Consider the nitrogen-oxygen bond lengths in NO2+ , NO2 , and NO3 . In which ion is the bond predicted to be longest? In which is it predicted to be the shortest? Explain briefly.7.47 Which of the species listed has a Lewis structure with only one lone pair of electrons? F2 , CO32 , CH4 , PH3 7.48 Identify what is incorrect in the Lewis structures shown for BBr3 and SO2 7.49 Identify what is incorrect in the Lewis structures shown for O3 and XeF4 .7.50 Chemical species are said to be isoelectronic if they have the same Lewis structure (regardless of charge). Consider these ions and write a Lewis structure for a neutral molecule that is isoelectronic with each of them, (a) CN , (b) NH4+ . (c) CO32 7.51 Explain the concept of wave interference in your own words. Distinguish between constructive and destructive interference.7.52 How does orbital overlap explain the buildup of electron density between nuclei in a chemical bond?7.53 How do sigma and pi bonds differ? How are they similar?7.54 CO , CO2 , CH3OH , and CO32 , all contain carbon-oxygen bonds. Draw Lewis structures for these molecules and ions. Given that double bonds are stronger than single bonds and triple bonds are stronger than double bonds, rank the four species in order of increasing C—O) bond strength.7.55 Draw the Lewis dot structure of the following species and identify the number of pi bonds in each. (a) CS2 , (b) CH3Cl , (c) NO2 , (d) SO2 7.56 Draw the Lewis dot structures of the following compounds and identify the number of pi bonds in each. (a) Cl2O , (b) H2CCH2 , (c) HCCCN , (d) SiO2 7.57 What observation about molecules compels us to consider the hybridization of atomic orbitals?7.58PAE 7.59 What type of hybrid orbital is generated by combining the valence s orbital and all three valence p orbitals of an atom? How many hybrid orbitals result?7.60 What type of hybridization would be expected for the central atom X in each of the following Lewis structures?7.61 What hybrid orbitals would be expected for the central atom in each of the following molecules? (a) GeCl4 , (b) PBr3 , (c) BeF2 , (d) SO2 7.62 What type of hybridization would you expect for the carbon atom in each of the following species? (a) CO , (b) CO2 , (c) H2CO , (d) CH2F2 7.63 What physical concept forms the premise of VSEPR theory?7.64 Predict the geometry of the following species, (a) (b) (c) (d)7.65PAE 7.66PAE 7.67PAE 7.68 Give approximate values for the indicated bond angles. (a) Cl—S—Cl in SCl2, (b) N—N—O in N2O, (c) bond angles marked as 1, 2, and 3 in the following structure for vinyl alcohol:7.69 Propene has the chemical formula Describe the overall shape of the molecule by considering the geometry around each carbon atom.7.70PAE 7.71PAE 7.72 How does an MSN differ from amorphous silica so that is has improved biocompatibility?7.73PAE 7.74 In a lattice, a positive ion is often surrounded by eight negative ions. We might reason, therefore, that the lattice energy should be related to eight times the potential of interaction between these oppositely charged particles. Why is this reasoning too simpler?7.75 Use the concept of lattice energy to rationalize why sodium fluoride dissolves in water, whereas calcium fluoride does not. Extending this reasoning, would you expect magnesium fluoride to be soluble?7.76PAE 7.77PAE 7.78PAE 7.79PAE 7.80PAE 7.81PAE 7.82PAE 7.83PAE 7.84 Which of the following molecules is least likely to actually exist OF4,SF4,SeF4 , or TeF4 ? Why?7.85 Consider the molecule whose structure is shown below. (a) How many carbon atoms are sp3 hybridized? (b) What is the shape of the molecule around the carbon atom marked A? (c) What is the shape of the molecule around the carbon atom marked B?7.86 Nitrogen triiodide, NI3(s) , is unstable and will spontaneously detonate to form a bright purple cloud of nitrogen and iodine gases accompanied with a loud ‘bang,” which suggests a release of energy. Considering the bonds involved, explain why this reaction is energy.7.87 Nitrogen is capable of forming single, double, or triple bonds, and the figure that follows shows the potential energy as a function of internuclear distance for each of these types of bonds. Match the three curves in the figure (A, B, and C) to the three types of bonds. Explain your reasoning.7.88 The N5+ cation has been synthesized and studied. Consider the possible Lewis structure below. Indicate the hybridization expected for each nitrogen atom and the expected bond angles. Assuming that the structure shown above is correct, how many of the five nitrogen atoms would always lie in the same plane?7.89PAE 7.90PAE 7.91 A Lewis structure for the oxalate ion is shown below. (One or more other resonance forms are also possible.) What is the correct charge on the oxalate ion? What type of orbital hybridization is expected for each of the carbon atoms in this structure? How many sigma bonds and how many pi bonds does the structure contain?7.92PAE 7.93 An unknown metal M forms a chloride with the formula This chloride compound was examined and found to have a trigonal pyramidal shape. Draw a Lewis structure for that is consistent with this molecular geometry. Use your structure to propose an identity for the metal M and explain how you have nude your choice.7.94PAE 7.95PAE 7.96 Consider the hydrocarbons whose structures are shown below. Which of these molecules would be planar, meaning that all of the atoms must lie in the same plane? Explain your answer in terms of orbital hybridizations.7.97 Consider the structure shown below for as well as any other important resonance structures. (a) What is the expected O—N—O bond angle in this structure? (b) The molecule contains N—O bonds of two different lengths. How many sborter N—O bonds would be present?7.98PAE 7.99PAE 7.100PAE 7.101 Lead selenide nanocrystals may provide a breakthrough in the engineering of solar panels to be efficient enough to be an economical source of electricity. Selenium is generally considered a nonmetal while lead is considered a metal. Is this distinction enough to suggest that this compound should be ionic? Explain your answer.7.102PAE 7.103PAE 7.104 Hydrogen azide, HN3 , is a liquid that explodes violently when subjected to shock. In the HN3 molecule, one nitrogen—nitrogen bond length has been measured at 112 pm and the other at 124 pm. Draw a Lewis structure that accounts for these observations. Explain how your structure reflects these experimental facts.7.105PAE 7.106PAE 7.107 How do the Lewis symbols for C, Si, and Ge reflect the similarity in their electron configurations?7.108PAE 7.109PAE 1CO • describe the arrangement of atoms in the common cubic crystal lattices and calculate the packing efficiency for a lattice.• use bind theory to describe bonding in solids.4CO 5CO 6CO 7CO • explain the connection between intermolecular forces and properties such as boiling point and vapor pressure.9CO 10CO 8.1PAE Why is the C 60form of carbon called buckminsterfullerene?8.3PAE 8.4PAE What is the relationship between the structures of buckminsterfullerene and carbon nanotubes?Use the web to look up information on nanotubes. Distinguish between single-walled and double-walled nanotubes.8.7PAE 8.8PAE 8.9PAE 8.10PAE 8.11PAE 8.12PAE 8.13 What is the coordination number of atoms in the diamond structure?8.14PAE 8.15PAE 8.16 Iridium forms a face-centered cubic lattice, and an iridium atom is 271.4 pm in diameter. Calculate the density of iridium.8.17 Europium forms a body-centered cubic unit cell and has a density of 4.68g/cm3 . From this information, determine the length of the edge of the cubic cell.8.18 Manganese has a body-centered cubic unit cell and has a density of 7.88g/cm3 . From this information, determine the length of the edge of the cubic cell.8.19PAE 8.20 How many electrons per atom are delocalized in the sea of electrons model for the following metals? (a) iron, (b) vanadium, (c) silver 8.21PAE 8.22PAE 8.23PAE 8.24 What is the key difference between metallic bonding (in the sea of electrons model) and ionic bonding (as described in Chapter 7) that explains why metals conduct electricity and ionic solids do not?8.25 Draw a depiction of the band structure of a metal. Label the valence band and conduction band.8.26PAE 8.27PAE 8.28PAE 8.29PAE 8.30PAE 8.31PAE 8.32PAE 8.33PAE Suppose that a device is using a 15.0-mg sample of silicon that is doped with 1105 (by mass) phosphorus. How many phosphorus atoms are in the sample?8.35 What is an instantancous dipole?8.36 Why are dispersion forces attractive?8.37 If a molecule is not very polarizable, how will it respond to an external electric field?8.38 What is the relationship between polarizability and dispersion forces?8.39 Under what circumstances are ion-dipole forces important?8.40 Which of the following compounds would be expected to form intermolecular hydrogen bonds in the liquid state? (a) CH3OCH3(dimethyl ether), (b) CH4(c) HF, (d) CH3CO2H(accetic acid), (e) Br2(f) CH3OH(methanol)8.41 What is the specific feature of N, O, and F that causes them to play a role in hydrogen bonding?8.42PAE 8.43 Identify the kinds of intermolecular forces (London dispersion, dipoledipole, or hydrogen bonding) that are the most important in each of the following substances. (a) methane (CH4) , (b) methanol (CH4OH) , (c) chloroform (CHCl3) , (d) benzene (C6H6) , (e) ammonia (NH3) , (f) sulfur dioxide (SO2)8.44PAE 8.45 Describe how interactions between molecules affect the vapor pressure of a liquid.8.46 What makes a chemical compound volatile?8.47 Answer each of the following questions with increases, decreases, or does not change. (a) If the intermolecular forces in a liquid increase, the normal boiling point of the liquid _____. (b) If the intermolecular forces in a liquid decrease, the vapor pressure of the liquid ______. (c) lf the surface area of a liquid decreases, the vapor pressure ____. (d) If the temperature of a liquid increases, the equilibrium vapor pressure ______.8.48 Why must the vapor pressure of a substance be measured only after dynamic equilibrium is established?8.49PAE 8.50PAE 8.51 Suppose that three unknown pure substances are liquids at room temperature. You determine that the boiling point of substance A is 53°C, that of substance B is 117°C, and that of substance C is 77°C. Based on this information, rank the three substances in order of their vapor pressures at room temperature.8.52 Rank the following hydrocarbons in order of increasing vapor pressure: C2H6,C10H22,CH4,C7H16,C22H46 .8.53PAE 8.54PAE 8.55PAE

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