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chemistry for engineering students
Chemistry For Engineering Students 4th Edition Lawrence S. Brown, Tom Holme - Solutions
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?
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.Figure 7.7
How is electronegativity defined?
Distinguish between electron affinity and electronegativity.
When two atoms with different electronegativities form a covalent bond, what does the electron distribution in the bond look like?
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
Why is a bond between two atoms with different electronegativities called a polar bond?
Based on the positions in the periodic table of the following pairs of elements, predict whether bonding between the two would be primarily ionic or covalent. Justify your answers.(a) Ca and Cl, (b) P and O,(c) Br and I, (d) Na and I(e) Si and Br, (f) Ba and F
In each group of three bonds, which bond is likely to be the most polar? Which will be the least polar? (a) C—H, O—H, S—H,(b) C—Cl, Cl—Cl, H—Cl, (c) F—F, O—F, C—F, (d) N—H, N—O, N—Cl
Considering the trends in electronegativity shown in Figure 7.7, explain why alloys that form between two or more transition metals are not ionic substances.Figure 7.7, 1 H 2.1 3 Li
Suppose that you wanted to make a diatomic molecule using two different halogen atoms. What combination of halogens would be the least polar? What combination would be the most polar?
Draw the Lewis structure for each of the following molecules.(a) CO,(b) H2S,(c) SF6,(d) NCl3
Write Lewis structures for these molecules. (a) Tetrafluoroethylene, C2F4, the molecule from which Teflon is made, (b) Acrylonitrile, CH2CHCN, the molecule from which Orlon® is made
Why is it impossible for hydrogen to be the central atom in the Lewis structure of a polyatomic molecule?
In the context of Lewis structures, what is resonance?
Draw resonance structures for(a) NO2 –, (b) NNO, and (c) HCO2 –.
How does the structure of a molecule that exhibits resonance justify the use of the term resonance hybrid?
Draw the Lewis structure of two resonance forms for ozone, O3. What prediction can you make about the relative lengths of the O—O bonds?
How does the existence of resonance structures for a molecule such as benzene explain its unusually unreactive chemical behavior?
Identify what is incorrect in the Lewis structures shown for BBr3 and SO2.(a) (b) : Br: : Br -B- Br:
Which of the species listed has a Lewis structure with only one lone pair of electrons? F2, CO32–, CH4, PH3.
Identify what is incorrect in the Lewis structures shown for O3 and XeF4.(a) (b) |:0—0—0:
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) C O 3 2–
Explain the concept of wave interference in your own words. Distinguish between constructive and destructive interference.
How does orbital overlap explain the buildup of electron density between nuclei in a chemical bond?
How do sigma and pi bonds differ? How are they similar?
CO, CO2, CH3OH, and CO3 2–, 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.
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
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
What observation about molecules compels us to consider the hybridization of atomic orbitals?
What type of hybridization would be expected for the central atom X in each of the following Lewis structures?(a) (b) (c) :O: :Cl—x— Cl: -X-
The number of hybrid orbitals formed must always be equal to the number of atomic orbitals combined. Suggest a reason why this must be true.
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?
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
What physical concept forms the premise of VSEPR theory?
Predict the geometry of the following species. (a) SO2, (b) BeCl2, (c) SeCl4, (d) PCl5
Predict the shape of each of the following molecules or ions. (a) PH4 +, (b) OSF4, (c) ClO2 –, (d) I3 –
Predict the shape of each of the following molecules or ions. (a) IF3, (b) ClO3 –, (c) TeF4, (d) XeO4
Which of these molecules would be linear? Which have lone pairs around the central atom? (a) XeF2, (b) CO2, (c) BeF2,(d) OF2
Propene has the chemical formula H2C═CH—CH3. Describe the overall shape of the molecule by considering the geometry around each carbon atom.
Describe why treatments like chemotherapy for cancer patient often have serious side effects. What is a strategy that could lessen such side effects?
Use the fundamental structure of mesoporous silica nanoparticles (MSN) to explain why they have such a large surface area.
How does an MSN differ from amorphous silica so that it has improved biocompatibility?
Draw a schematic picture of an MSN being used as a molecular engineering design selective drug delivery vehicle. Label all key components of the design.
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 simple?
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?
What type of bond is likely to form between one element with low ionization energy and another element with high electron affinity? Explain your answer.
Sketch a graph of the potential energy of two atoms as a function of the distance between them. On your graph, indicate how bond energy and bond distance are defined.
When a covalent bond forms, is energy absorbed or released? Explain how your answer is related to the graph you sketched in the previous problem.
Can fluorine atoms ever carry a partial positive charge in a molecule? Why or why not?
How is the concept of orbital overlap related to the wave nature of electrons?
Considering only s and p atomic orbitals, list all the possible types of hybrid orbitals that can be used in the formation of (a) Single bonds, (b) Double bonds, and (c) Triple bonds.
Describe why a central atom with four bonding pairs and one lone pair will have the lone pair in an equatorial rather than an axial location.
Describe what happens to the shape about the carbon atoms when a C═C double bond undergoes an addition reaction in which it is converted into a C—C single bond.
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? B H₂C CH3 CH C H₂ :O: H₂H₂ C H₂ CH3
Which of the following molecules is least likely to actually exist: OF4, SF4, SeF4, or TeF4? Why?
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 likely to release energy. 2
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.
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
Consider the Lewis structure below. Is this an ion? If so, what is its charge? ة==ة :O:
The following molecules have similar formulas, but each has a different shape. Draw Lewis structures for these compounds and then determine their molecular shapes.(a) SiF4, (b) KrF4, (c) SeF4
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
Methyl cyanoacrylate, C5H5NO2, is the compound commonly sold as super glue. The glue works through a polymerization reaction, in which molecules of methyl cyanoacrylate form strong chemical bonds to one another and to the surfaces being glued. This process is initiated by traces of water on the
Nearly all of the other elements form binary compounds with hydrogen. Based on the electronegativity values shown in Figure 7.7, with what category of elements will hydrogen form bonds in which the hydrogen atom carries a partial negative charge? With what category of elements will hydrogen form
A glass contains 250.0 g of warm water at 78.08C. A piece of gold at 2.308C is placed in the water. The final temperature reached by this system is 76.98C. What was the mass of gold? The specific heat of water is 4.184 J g-1 8C21 and that of gold is 0.129 J g-1 8C-1.Strategy We will need to assume
An unknown metal M forms a chloride with the formula MCl3. This chloride compound was examined and found to have a trigonal pyramidal shape. Draw a Lewis structure for MCl3 that is consistent with this molecular geometry. Use your structure to propose an identity for the metal M and explain how you
ΔHvap = 31.3 kJ/mol for acetone. If 1.40 kg of water were vaporized to steam in a boiler, how much acetone (in kg) would need to be vaporized to use the same amount of heat?
Using pentagons, draw arrangements that demonstrate low packing efficiency and higher packing efficiency.
Although we often classify bonds between a metal and a nonmetal as ionic, not all such bonds have the same degree of ionic character. Consider the series of tin(IV) halides: SnF4, SnCl4, SnBr4, and SnI4. Rank these compounds in terms of expected ionic character, from most ionic to least ionic. What
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. Cyclohexane Benzene Methylbenzene
Consider the structure shown below for N2O3 as well as any other important resonance structures.(a) What is the expected O—N—O bond angle in this structure? (b) The N2O3 molecule contains N—O bonds of two different lengths. How many shorter N—O bonds would be present? :0: Ö=N- 0=N_N=0
Electrical engineers often use lithium niobate, LiNbO3, in designs for surface acoustic wave filters in devices such as cellular phones. What type(s) of bonding would you expect to be present in this compound?
One of the “grand challenges” for engineering identified by the U.S. National Academy of Engineering is the capture of carbon dioxide produced by the burning of fossil fuels. Although carbon and oxygen have significantly different electronegativities, CO2 cannot easily be separated from air by
Another “grand challenge” for engineering is managing the nitrogen cycle. Use the nature of the chemical bond in diatomic nitrogen to explain why any management is needed for this biogeochemical cycle. With so much nitrogen available in the atmosphere, why are engineering solutions needed to
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
Both ozone, O3, and oxygen, O2, absorb UV light in the upper atmosphere. The ozone, however, absorbs slightly longer wavelengths of UV light!wavelengths that would otherwise reach the surface of the planet. (a) How can Lewis structures help explain the bonding difference between ozone and oxygen
Nitrogen is the primary component of our atmosphere. It is also used as an inert reagent to fill containers of chemicals that might react with the oxygen in air. Draw a Lewis structure of nitrogen and use this drawing to help explain why nitrogen does not react readily with other molecules.
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
If leads are attached to the opposite sides of a crystal of sodium chloride, it does not conduct electricity. Distilled water does not conduct electricity either. Yet, if the sodium chloride crystal is dissolved in distilled water, the resulting solution does conduct electricity. Use pictures at
How does electronegativity relate to the periodic trends of atomic properties? How does effective nuclear charge, the concept invoked to understand those trends, also help explain the trends in electronegativity?
How do the Lewis symbols for C, Si, and Ge reflect the similarity in their electron configurations?
Use Lewis symbols to describe how free radical polymerization occurs.
When free radical polymerization occurs, how does the hybridization change the carbon atoms involved?
Show that the packing efficiency of the face-centered cubic structure is actually 74%, as we have claimed.Strategy This is essentially a geometry problem, and it requires us to understand the location of and spacing between the atoms in the fcc lattice. To find the packing efficiency, we’ll need
How many solid forms of elemental carbon are known?
Why is the C60 form of carbon called buckminsterfullerene?
What property of diamond leads to the most engineering applications? Which types of applications would benefit from this property?
Which variables must be controlled and in what manner to produce diamonds from graphite?
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.
Use the web to look up the experimental conditions required to synthesize buckminsterfullerene in an electric arc. Would running an arc in air work?
Define packing efficiency.
Calculate the packing efficiencies for both two-dimensional arrangements shown in Figure 8.3.Figure 8.3 Large gaps with rows lined up Smaller gaps with rows offset from one another
Using circles, show that a cubic structure (squares in 2D) has a lower coordination number than a hexagonal structure.
Explain why hcp and ccp structures have the same coordination number.
What is the coordination number of atoms in the diamond structure?
Explain why graphite is described as having a layered structure.
Polonium is the only metal that forms a simple cubic crystal structure. Use the fact that the density of polonium is 9.32 g/cm3 to calculate its atomic radius.
Iridium forms a face-centered cubic lattice, and an iridium atom is 271.4 pm in diameter. Calculate the density of iridium.
Europium forms a body-centered cubic unit cell and has a density of 4.68 g/cm3. From this information, determine the length of the edge of the cubic cell.
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