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All Textbook Solutions for Chemistry for Engineering Students

1CO 2CO Draw pictures to illustrate simple chemical phenomena (like the differences among solids, liquids, and gases) on the molecular scale.Explain the difference between inductive and deductive reasoning in your own words.Use appropriate techniques to convert measurements from one unit to another.Express the results of calculations using the correct number of significant figures.What are the components involved?How do those components interact or connect to each other?What is the ultimate function of the whole system?1.1PAE In what country is most of the world’s cobalt mined? What events in that country dramatically affected the price of cobalt?In what types of technology do the elements designated as critical materials generally play important roles?Based on the information in Figure 1.1, which three elements would you argue are the most critical among the “critical materials”? Justify your answer.1.5PAE 1.6PAE When we make observations in the laboratory, which perspective of chemistry are we normally using?Which of the following items are matter and which are not? (a) a flashlight, (b) sunlight, (c) an echo, (d) air at sea level, and (e) air at the top of Mount Everest Which macroscopic characteristics differentiate solids, liquids, and gases? (List as many as possible)1.10 Do the terms element and atom mean the same thing? If not, how do they differ?1.11 Label each of the following as either a physical process or a chemical process. (a) rusting of an iron bridge, (b) melting of ice, (c) burning of a wooden stick, (d) digestion of a baked potato. (e) dissolving of sugar in water 1.12 Why do physical properties play a role in chemistry if they do not involve any chemical change?1.13 Physical properties may change because of a chemical change. For example, the color of an egg white changes from clear to white because of a chemical change when it is cooked. What is another common situation in which a chemical change also leads to a physical change?1.14 Which part of the following descriptions of a compound or element refers to its physical properties and which to its chemical properties? (a) Calcium carbonate is a white solid with a density of 2.71 g/cm. It reacts readily with an acid to produce gaseous carbon dioxide. (b) Gray powdered zinc metal reacts with purple iodine to give a white compound.1.15 We used the example of attendance at a football game to emphasize the nature of observations. Describe another example where deciding how to count subjects of interest could affect the observation.1.16 Complete the following statement: Data that have a small random error but otherwise fall in a narrow range are (a) accurate, (b) precise, or Cc) neither.1.17 Complete the following statement: Data that have a large systematic error can still he (a) accurate, (b) precise, or (c) neither.1.18 Two golfers are practicing shots around a putting green. Each golfer takes 20 shots. Golfer 1 has 7 shots within 1 meter of the hole, and the other 13 shots are scattered around the green. Golfer 2 has 17 shots that go into a small sand trap near the green and 3 just on the green near the trap. Which golfer is more precise? Which is more accurate?1.19PAE 1.20 Suppose that you are waiting at a corner for a bus. Three different routes pass this particular corner. You see buses pass by from the two routes that you are not interested in taking. When you say to yourself, “My bus must be next,” what type of reasoning (deductive or inductive) are you using? Explain your answer.1.21 When a scientist looks at an experiment and then predicts the results of other related experiments, which type of reasoning is she using? Explain your answer.1.22 What is the difference between a hypothesis and a question?1.23 Should the words theory and model be used interchangeably in the context of science? Defend your answer using information found in a web search.1.24 What is a law of nature? Are all scientific laws examples of laws of nature?1.25 Describe a miscommunication that can arise because units are not included as part of the information.1.26 What is the difference between a qualitative and a quantitative measurement?1.27 Identify which of the following units are base units in the SI system: grams, meters, joules, liters, amperes.1.28 What is a “derived” unit?1.29 Rank the following prefixes in order of increasing size of the number they represents : centi-, giga-, nano-, and kilo-.1.30 The largest computers now include disk storage space measured in petabytes. How many bytes are in a petabyte? (Recall that in computer terminology, the prefix is only “close” to the value it designates in the metric system.)1.31PAE 1.32 Use the web to determine how the Btu was initially established. For the engineering applications where this unit is still used today, why is it a sensible unit?1.33 How many micrograms are equal to one gram?1.34 Convert the value 0.120 ppb into ppm.1.35 How was the Fahrenheit temperature scale calibrated? Describe how this calibration process reflects the measurement errors that were evident when the temperature scale was devised.Superconductors are materials that have no resistance to the flow of electricity, and they hold great promise in many engineering applications. But to date, superconductivity has only been observed under cryogenic conditions. As of 2016, the highest temperature at which superconductivity has been observed is 203 K. Convert this temperature to both °C and °F.1.37 Express each of the following temperatures in Kelvins. (a) -10.°C, (b) 0.00 °C, (c) 280 °C, (d) 1.4103 °C 1.38 Express (a) 275 oC in K, (b) 25.55 K in oC, (c) -47.0 oC in oF, and (d) 100 oF in K.1.39 Express each of the following numbers in scientific notation. (a) 62.13, (b) 0.000414, (c) 0.0000051, (d) 871,000,000, (e) 9100 1.40 How many significant figures are there in each of the following? (a) 0.136 m, (b) 0.0001050 g, (c) 2.700103nm , (d) 6104L , (e) 56003 cm3 1.41 How many significant figures are present in these measured quantities? (a) 1374 kg, (b) 0.00348 s, (c) 5.619 nm, (d) 2.475103cm , (e) 33.1 mL Perform these calculations and express the result with the proper number of significant figures. (a) (4.850g2.34g)/1.3mL (b) V=r3, where r=4.112cm (c) (4.66103)4.666 (d) 0.003400/65.2 1.43 Calculate the following to the correct number of significant figures. Assume that all these numbers are measurements. (a) x=17.2+65.182.4 (b) x=13.0217/17.10 (c) x=(0.0061020)(2.0092)(1200.00) (d) x=0.0034+( 0.0034)2+4(1.000)(6.3 10 1)(2)(1.000)1.44 In an attempt to determine the velocity of a person on a bicycle, an observer uses a stopwatch and finds the length of time it takes to cover 25 “squares” on a sidewalk. The bicycle takes 4.82 seconds to travel this far. A measurement of one of the squares shows that it is 1.13 m long. What velocity, in m/s, should the observer report?1.45 A student finds that the mass of an object is 4.131 g and its volume is 7.1 mL. What density should be reported in g/mL?1.46 Measurements indicate that 23.6% of the residents of a city with a population of 531,314 are college graduates. Considering significant figures, how many college graduates are estimated to reside in this city?1.47 A student weighs 10 quarters and finds that their total mass is 56.63 grams. What should she report as the average mass of quarter based on her data?1.48 A rock is placed on a balance and its mass is determined as 12.1 g. When the rock is then placed in a graduated cylinder that originally contains 11.3 mL of water, the new volume is roughly 17 rnL. How should the density of the rock be reported?1.49 A package of eight apples has a mass of 1.00 kg. What is the average mass of one apple in grams?1.50PAE 1.51 A person measures 173 cm in height. What is this height in meters? Feet and inches?1.52 The distance between two atoms in a molecule is 148 pm. What is this distance in meters?1.53 Carry out the following unit conversions. (a) 3.47106g to g , (b) 2.73104L to mL, (c) 725 ns to s, (d) 1.3 m to km.1.54 Carry out each of the following conversions. (a) 25.2 m to km, (b) 36.3 km to m, (c) 487 kg to g, (d) 1.32 L to mL, (e) 55.9 dL to L, (f) 625 L to cm3 1.55 Convert 22.3 mL to (a) liters, (b) cubic inches, and (c) quarts.1.56 If a vehicle is travelling 92 m/s, what is its velocity in miles per hour? (0.62 miles=1.00 km)1.57 A load of asphalt weights 245 lb. and occupies a volume of 55.0 L. What is the density of this asphalt in g/L?1.58 One square mile contains exactly 640 acres. How many square meters are in one acre?1.59 A sample of crude oil has a density of 0.87 g/mL. What volume in liters does a 3.6-kg sample of this oil occupy?1.60 Mercury has a density of 13.6 g/mL. What is the mass of 4.72 L of mercury?1.61 The area of the 48 contiguous states is 3.02106mi2 . Assume that these states are completely flat (no mountains and no valleys). What volume of water, in liters, would cover these states with a rainfall of two inches?1.62 The dimensions of aluminium foil in a box for sale in supermarkets are 66 yards by 12 inches. The mass of the foil is 0.83 kg. If its density is 2.70 g/cm, then what is the thickness of the foil in inches?1.63PAE 1.64 Wire is often sold in pound spools according to the wire gauge number. That number refers to the diameter of the wire. How many meters are in a 10-lb. spool of 12-gauge aluminium wire? A 12-gauge wire has a diameter of 0.0808 in. and aluminium has a density of 2.70g/cm3 , (V=r2l)1.65 An industrial engineer is designing a process to manufacture bullets. The mass of each bullet must be within 0.2 5% of 150 grains. What range of bullet masses, in mg, will meet this tolerance? 1 grain = 64.79891 mg.1.66 An engineer is working with archaeologists to create a realistic Roman village in a museum. The plan for a balance in a marketplace calls for 100 granite stones, each weighing 10 denarium. (The denarium was a Roman unit of mass: 1 denarium = 3.396 g.) The manufacturing process for making the stones will remove 20% of the material. If the granite to be used has a density of 2.75g/cm3, what is the minimum volume of granite that the engineer should order?1.67 On average, Earth’s crust contains about 8.1 % aluminium by mass. If a standard I 2-ounce soft drink can contains approximately 15.0 g of aluminium, how many cans could be made from one ton of the Earth’s crust?1.68PAE 1.69 The “Western Stone” in Jerusalem is one of the largest stone building blocks ever to have been used. It has a mass of 517 metric tons and measures 13.6 m long, 3.00 m high and 3.30 m wide. What is the density of this rock in g/cm3? (1 metric ton 1000 kg)A load of bauxite has a density of 3.15 g/cm3. If the mass of the load is 115 metric tons, how many dump trucks, each with a capacity of 12 cubic yards, will be needed to haul the whole load?1.71 Is touch screen technology better described as a single design or as a more complex system? Explain your answer.1.72PAE 1.73 Why are two separate ITO layers required in a touch screen display?1.74 What are the two properties of ITO that make it serve its function in touch screen applications?1.75 What does it mean that ITO films are made by deposition? In what phase do materials begin, and in what phase do they end up?1.76 How does Gorilla Glass differ from more commonly found alumina silicate glass?1.77 How can a liquid be distinguished from a fine powder? What type of experiment or observation might be undertaken?1.78 Some farmers use ammonia, NH3, as a fertilizer. This ammonia is stored in liquid form. Use the participate perspective to show the transition from liquid ammonia to gaseous ammonia.1.79 Use a molecular-level description to explain why gases are less dense than liquids or solids.1.80 All molecules attract each other to some extent, and the attraction decreases as the distance between particles increases. Based on this idea, which state of matter would you expect has the strongest interactions between particles: solids, liquids, or gases?1.81 Draw a molecular-scale picture to show how a crystal differs from a liquid.1.82 Which of the following molecular-scale diagrams best represents a pure compound? Explain your answer.1.83 What type of transition is represented in the following molecular-scale illustration?1.84 A student was given two metal cubes that looked similar. One was 1.05 cm on an edge and had a mass of 14.32 grams; the other was 2.66 cm on a side and had a mass of 215.3 grams. How can the student determine if these two cubes of metal are the same material using only the data given?1.85 Battery acid has a density of 1.285 g/mL and contains 38.0% sulfuric acid by mass. Describe how you would determine the mass of pure sulfuric acid in a car battery, noting which item(s) you would have to measure or look up.1.86 Unfermented grape juice used to make wine is called a ‘must.” The sugar content of the must determines whether the wine will be dry or sweet. The sugar content is found by measuring the density of the must. If the density is lower than 1.070 g/mL, then sugar syrup is added until the density reaches 1.075 g/mL. Suppose that you have a sample taken from a must whose mass is 47.28 g and whose volume is 44.60 mL. Describe how you would determine whether or not sugar syrup needs to be added and if so, how would you estimate how much sugar syrup to add?”1.87 A solution of ethanol in water has a volume of 54.2 mL and a mass of 49.6 g. what information would you need to look up and how would you determine the percentage of ethanol in this solution?1.88 Legend has it that Archimedes, a famous scientist of Ancient Greece, was once commanded by the king to determine if a crown he received was pure gold or a gold—silver alloy. He was not allowed, however, to damage the crown (by slicing off a piece, for example). If you were assigned this same task, what would you need to know about both gold and silver, and how would you make a measurement that would tell you if the crown was pure gold?1.89 Imagine that you place a cork measuring 1.30cm4.50cm3.00cm in a pan of water. On top of this cork, you place a small cube of lead measuring 1.15 cm on a side. Describe how you would determine if the combination of the cork and lead cube will still float in the water. Note any information you would need to look up to answer the question.1.90 A calibrated flask was filled to the 25.00-mL mark with ethyl alcohol and was found to have a mass of 19.7325 g. In a second experiment, 25.0920 g of metal beads were put into the container and the flask was again filled to the 25.00-mL mark. The total mass of the metal plus the alcohol was 43 .0725 g. Describe how to determine the density of the metal sample.Name at least three common polymers and give examples of their uses.2CO Describe the nuclear model for the atom and identify the numbers of protons, electrons, and neutrons in a particular isotope from its chemical symbol.4CO 5CO 6CO 7CO 8CO 9CO 10CO 2.1PAE How do polymers compare to their respective monomers?Look around you and identify several objects that you think are probably made from polymers.2.4PAE The fact that a polymer’s physical properties depend on its atomic composition is very important in making these materials so useful. Why do you think this would be so?One application of conductive polymers is in photovoltaic solar cells. Such devices have traditionally been silicon based. What possible advantages might conducting polymers offer?2.7PAE 2.8PAE Why is the number of protons called the atomic number?2.10 Which isotope in each pair contains more neutrons? (A) 35Cl or 33S, (b) 19F or 19Ne, (c) 63Cu or 65Zn, (d) 126I or 127Te 2.11 Define the term isotope.2.12 Write the complete atomic symbol for each of the following isotopes. (a) carbon-13, (b) phosphorus-31, (c) sodium-23, (d) boron-10 2.13 How many electrons, protons, and neutrons are there in each of the following atoms? (a) 24Mg, (b) 119Sn, (c) 232Th, (d) 13C, (e) 63Cu, (f) 205Bi 2.14 Consider the following nuclear symbols. How many protons, neutrons, and electrons does each element have? What elements do R, T, and X represent? (a) 1430R (b) 3989T (c) 55133X 2.15 Mercury is 16.716 times more massive than 12C. What is the atomic weight of mercury? Remember to express your answer with the correct number of significant figures.The element gallium, used in gallium arsenide semiconductors, has an atomic weight of 69.72 amu. There are only two isotopes of gallium, Ga with a mass of 6.9257 amu and Ga with a mass of 70.9249 amu. What are the isotopic abundances of gallium? Gallium melts just above room temperature 2.17 The atomic weight of copper is 63.55 amu. There are only two isotopes of copper, 63Cu with a mass of 62.93 amu and 65Cu with a mass of 64.93 amu. What is the percentage abundance of each of these two isotopes?The following table presents the abundances and masses of the isotopes of zinc. What is the atomic weight of zinc?2.19 Naturally occurring uranium consists of two isotopes, whose masses and abundances are shown below: Only 235U can be used as fuel in a nuclear reactor, so uramium for use in the nuclear industry must be enriched in this isotope. If a sample of enriched uranium has an atomic weight of 235.684 amu, what percentage of 235LT is present?2.20PAE 2.21PAE 2.22 Provide the symbol of the following monoatomic ions, given the number of protons and electrons in each. (a) 8 protons, 10 electrons, (b) 20 protons, 18 electrons. (c) 53 protons, 54 electrons, (d) 26 protons, 24 electrons.2.23PAE 2.24 Identify each of the following species as an anion, a cation, or a molecule. (a) CO32 , (b) CO2, (c) NH4+, (d) N3- (e) CH3COO-2.25 Write the atomic symbol for the element whose ion has a 2-charge, has 20 more neutrons than electrons, and has a mass number of 126.2.26 In what region of the periodic table are you likely to find elements that form more than one stable ion?2.27PAE 2.28PAE 2.29PAE 2.30 Using Coulomb’s law, explain how the difference between attractive and repulsive interactions between ions in expressed mathematically.2.31PAE 2.32 Which of the following formulas contains the most hydrogen atoms? C2H6, (NH4)2CO3, H2SO4, or Fe(OH)3.2.33PAE 2.34PAE 2.35PAE 2.36 Explain the difference between a molecular formula and an empirical formula.2.37 Why are empirical formulas preferred for describing polymer molecules?2.38 The molecular formula for the ethylene monomer is C2H4. What is its empirical formula?239 Polybutadiene is a synthetic elastomer, or rubber. The corresponding monomer is butadiene, which has the molecular formula C4H6. What is the empirical formula of butadiene?2.40 What distinguished the work of Mendeleev that caused scientists to accept his concept of the periodic table when others before him were not believed?2.41 How does the periodic table help to make the study of chemistry more systematic?2.42 What is a period in the periodic table? From what does it derive its name?2.43 Name of the group to which each of the following elements belongs. Name the group to which each of the solving elements belongs. (a) K, (b) Mg, (c) Ar, (d) Br 2.44PAE 2.45PAE 2.46 Why are nonmetals important even though they account for only a very small fraction of the elements in the periodic table?2.47PAE A materials engineer has filed for a patent for a new alloy to be used in golf club heads. The composition by mass ranges from 25 to 31% manganese, 6.3 to 7.8% aluminum, 0.65 to 0.85% carbon, and 5.5 to 9.0% chromium, with the remainder being iron. What are the maximum and minimum percentages of iron possible in this alloy? Use Figure 2.12 to snake a prediction about how the density of this alloy would compare with that of iron; justify your prediction.2.49PAE 2.50 A materials engineer wants to make a new material h taking pure silicon and replacing some fraction of the silicon atoms with other atoms that have similar chemical properties. Based on the periodic table, what elements probably should be tried first?2.51PAE 2.52PAE 2.53 What is meant by the phrase organic chemistry?2.54 Based on what you have learned in this chapter, would you classify the chemistry of polymers as organic or inorganic? Why?2.55 What is a functional group? How does the concept of the functional group help to make the study of organic chemistry more systematic?2.56PAE 2.57PAE 2.58PAE 2.59 The accompanying figure shows the structure of gamma-aminoburanoic acid, or GABA. This molecule is a neurotransmitter. Some of the effects of alcohol consumption are due to the interaction between ethanol and GABA. Write the correct molecular formula for this compound.2.60PAE 2.61 Name the following covalent compounds: (a) N2O5, (b) S2Cl2, (c) NBr3, (d) P4O10 2.62PAE 2.63PAE 2.64PAE 2.65PAE 2.66PAE 2.67PAE 2.68 What is a free radical? How are free radicals important in the formation of polyethylene?2.69PAE 2.70 Why do you think an inhibitor molecule is needed to induce the polymerization of ethylene?2.71 Use the web to determine the amount of low-density polyethylene and high-density polyethylene produced annually in the United States. Which uses predominate in the applications of these two materials?2.72 How can an element have an atomic weight that is not an integer?2.73 Explain the concept of a “weighted” average in your own words.2.74 The accompanying table provides the identity of the two naturally occurring isotopes for four elements and the atomic weights for those elements. (In each case, the two isotopes differ in mass number by two.) Which element has the mass spectrum shown? Explain your answer.2.75 Chlorine has only two isotopes, one with mass 35 and the other with mass 37. One is present at roughly 75% abundance, and the atomic weight of chlorine on a periodic table is 35.45. Which must be the correct mass spectrum for chlorine?2.76PAE 2.77PAE 2.78PAE 2.79PAE 2.80 Of the following elements, which two would you expect to exhibit the greatest similarity in physical and chemical properties? CL, P, S, Se, Ti. Explain your choice.2.81 How do binary compounds with hydrogen illustrate the concept of periodicity?2.82PAE 2.83PAE 2.84 Early attempts to arrange the elements often focused on atomic weight. Mendeleev considered a number of properties in addition to atomic weight, so he realized that some elements seemed out of place when ordered by atomic weight. Using the modern periodic table, identify elements for which Mendeleev must have had to switch the order in order to get the correct sequence of elements.2.85 Describe how the saying “opposites attract” corresponds with the mathematical representation of Coulomb’s law shown in Equation 2.1. Remember that attractive forces have negative values and repulsive forces have positive values.2.86 For some uses, the relative abundance of isotopes must be manipulated. For example, a medical technique called boron neutron capture therapy needs a higher fraction of 10B than occurs naturally to achieve its best efficiency. What would happen to the atomic weight of a sample of boron that had been enriched in 10B? Explain your answer in terms of the concept of a weighted average.2.87 What is the heaviest element to have an atomic weight that is roughly twice its atomic number? What does this suggest must he true about the nuclei of atoms with higher atomic numbers?2.88 Describe how you can identify the isotope, X, in this puzzle. The nucleus contains one more neutron than proton, and the mass number is nine times larger than the charge on the ion X3+.2.89PAE 2.90 Naturally occurring europium has an average atomic weight of 151.964 amu. If the only isotopes of europium present are 151Eu and 153Eu, describe how you would determine the relative abundance of the two isotopes. Include in your description any information that would need to be looked up.2.91 Strontium has four stable isotopes. Strontium—84 has a very low natural abundance, but 86Sr, 87Sr, and 88Sr are all reasonably abundant. Knowing that the atomic weight of strontium is 87.62, which of the more abundant isotopes predominates?2.92 A candy manufacturer makes chocolate-covered cherries. Although all of the products look roughly the same, 3% of them are missing the cherry. The mass of the candy with a cherry is 18.5 g; those missing the cherry weigh only 6.4 g. (a) How would you compute the average mass of a box of 100 of these chocolate covered cherries from this manufacturer? (b) I low is this question analogous to the determination of atomic weights?2.93PAE 2.94 Use a molecular level description to distinguish between LDPE and HDPE.2.95 Engineers who design bicycle frames are familiar with the densities of aluminium (2.699 g/cm3), steel (7.87 g/cm3), and titanium (4.507 g/cm3). How does this information compare with Figure 2.12, and what would it suggest for changes in this figure if more shades were used for the density colour-coding? (Iron is the principal component of steel)2.96 Use the web to look up the density of different forms of steel, such as stainless steel or magnetic steel, and discuss whether or not the differences in the densities follow what might he predicted by looking at the periodic properties of elements.2.97 LDPE has a density in the range of 0.915—0.935 g/cm3, and HDPF has a density in the range of 0.940—0.965 g/cm3. You receive a small disk, 2.0 cm high with a 6.0-cm diameter, from a manufacturer of polyethylene, but its label is missing. You measure the mass of the disk and find that it is 53.8 g. Is the material HDPE or LDPE?• describe the chemical processes used in biomass production and conversion to biofuels.2CO list at least three quantities that must be conserved in chemical reactions.Write balanced chemical equations for simple reactions, given either an unbalanced equation or a verbal description.5CO 6CO Interconvert between mass, number of molecules, and number of moles.Determine a chemical formula from elemental analysis (i.e., from % composition).define the concentration of a solution and calculate the molarity of solutions from appropriate data.Calculate the molarity of solutions prepared by dilution or calculate the quantities needed to carry out a dilution to prepare a solution of a specified concentration.11CO 12CO 13CO write molecular and ionic equations for acidbase neutralization reactions.3.1PAE 3.2PAE 3.3PAE A newspaper article states that biomass has actually been used as an energy source throughout human history. Do you agree or disagree with this statement? Defend your answer.3.5PAE 3.6PAE Which symbols are used to indicate solids, liquids, gases, and aqueous solutions in chemical equations?How is the addition of heat symbolized in a chemical equation? The addition of light energy?3.9PAE 3.10 Define the term stoichiometric coefficient.3.11 Balance these equations. (a) Al(s) + O2(g)( Al2O3(s) (b) N2(g) + H2(g) (NH3(g) (c) C6H6(l) + O2(g) ( H2O(l) + CO2(g)3.11 Balance the following equations. (a) CaC2(s) + H2O(l)( Ca(OH)2(s) + C2H2(g) (b) (NH4)2CrO7(s) ( Cr2O3(s) + N2(g) + H2O (g) (c) CH3NH2(g) + O2(g) ( CO2(g) + N2(g) + H2O (g)3.13 An explosive whose chemical formula is C3H6N6O6 produces water, carbon dioxide, and nitrogen gas when detonated in oxygen. Write the chemical equation for the detonation reaction of this explosive.3.14 A number of compounds are used in cement, and reactions among them occur when water is added. In one, CaO reacts with Al2O3 and water to form Ca3Al2(OH)12. Write a bal- anced chemical equation for this process.3.15 Ethanol, C2H5OH is found in gasoline blends used in many parts of North America. Write a balanced chemi- <>cal equation for the combustion of C2H5OH to form CO2 and HA.3.16 Balance the following equations. (a) reaction to produce "super-phosphate" fertilizer: Ca3(PO4)2(s)+H2SO4(aq)( Ca(H2PO4)2(aq)+CaSO4(s) (b) reaction to produce diborane, B2H6: NaBH4(s) + H2SO4(aq) ( B2H6(g) + H2(g) + Na2SO4(aq) (c) reaction to produce tungsten metal from tungsten(VI) oxide: WO3(s)+ H2(g) ( W(s) + H2O(l) (d) decomposition of ammonium dichromate: (NH4)2Cr2O7(s)(N2(g)+H2O(l)+Cr2O3(s)3.17 Write balanced chemical equations for the following reactions. (a) production of ammonia, NH3(g), by combining N2(g) and H2(g) (b) production of methanolCH3OH(l), by combining H2(g) and CO(g) (c) production of sulfuric acid by combining sulfur, oxygen, and water 3.18 Diborane and related compounds were proposed as rocket fuels in the 1950s. A representative reaction for this class of molecules is that of B2H6 and O2 to form B2O3 and H2O. Write the balanced chemical equation for this process.3.19 Silicon nitride, Si3N4, is used as a reinforcing fiber in con- struction materials. It can be synthesized from silicon tetra- chloride and ammonia. The other product is ammonium chloride. Write the balanced chemical reaction for this 3.21PAE 3.20PAE 3.23PAE 3.22PAE 3.24 Classify the following compounds as electrolytes or non- electrolytes. (a) potassium chloride, KCl, (b) hydrogen peroxide H2O2, (c) methane, CH4, (d) barium nitrate, Ba(NO3)2.3.25 The following compounds are water-soluble. What ions are produced by each compound in aqueous solution? (a) KOH, (b) K2SO4, (c) LiNO3, (d) (NH4)2SO4.3.26 Decide whether each of the following is water-soluble. If soluble, tell what ions are produced. (a) Na2CO3, (b) CuSO4 ,(c) NiS, (d) BaBr2 3.27PAE 3.28 A packaging engineer is working on a new design for cold packs. A burst chamber in the pack will contain mL of water, which will be released and used to dis- solve ammonium nitrate. (a) If the solubility of NH4NO3 is 190 g/ 100 g H2O, what mass of this compound should be used with this amount of water? (b) The design speci- fications indicate that these chemicals can account for no more than 35% of the mass of the product. What would the product weigh if it just meets these design specs?3.29 Classify each of these as an acid or a base. Which are strong and which are weak? What ions are produced when each is dissolved in water? (a) KOH, (b)Mg(OH)2,(c) HClO, (d) HBr, (e) LiOH, (f) H2SO3.3.30 Define the term spectator ion.3.31 What is the difference between a total ionic equation and a net ionic equation?3.32 Balance the following equations and then write the net ionic equation. (a)(NH4)2CO3 (aq)+ Cu(NO3)2 (aq)( CuCO3 (s)+ NH4NO3(aq) (b) Pb(OH)2(s)+ HCl(aq) ( PbCl2(s) + H2O (l) (c) BaCO3(s) + HCl(aq)( BaCl2(aq) + H2O (l) + CO2(g) (d) CH3CO2H (aq)+ Ni(OH)2(s)( Ni(CH3CO2)2(aq) + H2O(l)3.33 Balance the following equations, and then write the net ionic equation. (a) Zn(s) + HC1(aq) ( H2(g) + ZnCl2(aq) (b) Mg(OH)2 (s)+ HCl (aq) ( MgCl2(aq) + H2O (l) (c) HNO3(aq) + CaCO3(s) ( Ca(NO3)2(aq) + H20(l) + CO2(g) (d) (NH4)2S (aq)+ FeCl3(aq)( NH4Cl (aq)+Fe2S3(s)3.34 In principle, it may be possible to engineer the trap- ping of carbon dioxide by a precipitation reaction with Ca(OH)2 to form calcium carbonate and water. Write the molecular, total ionic, and net ionic equations for this reaction.3.35 Explain the concept of the mole in your own words.3.36 How many entities are present in each of the following? (a) 3.21 mol argon atoms. (b) 1.3 × 10—12 mol marbles. (c) 3 × 106 mol water molecules. (d) 7.63 × 10-18 mol basketballs.3.37 If atypical grain of sand occupies a volume of 1.3 × 10-4 cm3, what is the volume (in cm3) of 1 mole of sand (ignoring the space between grains)? What is the volume in liters?3.38 Estimate the size of a particle 1 mole of which would fill your bedroom or dorm room.3.39 Calculate the molar mass of each of the following com- pounds. (a) Fe2O3, iron(III) oxide, (b) BCl3, boron trichlo- ride, (c)C6H8O6 ascorbic acid (vitamin C).3.40 Calculate the molar masses (in grams per mole) of each of the following. (a) cane sugar,C12H22O11, (b) laughing gas, N2O, and (c) vitamin A, C20H30O.3.41 Calculate the molar mass of each of these compounds and the mass percentage of each element. (a) PbS, lead(II) sulfide, galena, (b) C2H6, ethane, a hydrocarbon fuel, (c) acetic acid, an important ingredient in vinegar, (d) NH4NO3, ammonium nitrate, a fertilizer.3.42PAE 3.43 Calculate the molar mass of the following compounds. (a) magnesium phosphate, (b) sodium sulfide, (c) dinitro- gen tetroxide 3.44 Determine the molar mass of these ceramic materials. (a) HfN, (b) ThO2, (c) BaTiO3 A chemist needs exactly 2 moles of KNO3 to make a solution. What mass of solid KNO3 must be used?3.46 What mass of ozone (O3) contains 4.5 moles of the substance?3.47 Calculate the mass in grams of each the following. (a) 2.5 mol of aluminum, (b) 1.25 × 10—3 mol of iron, (c) 0.015 mol of calcium, (d) 653 mol of neon 3.48 Calculate the mass in grams of 13.5 mol of (a) vinyl chlo- ride, C2H3Cl, the starting material for a plastic, (b) cap- saicin, C18H27NO3, the substance that makes red chili peppers "hot," and (c) stearic acid, C18H36O2 used in soaps.3.49 How many moles are present in the given quantities of ex- plosives? (a) 358.1 g trinitrotoluene (TNT), C7H5N3O6 (b) 82.6 g nitromethane, CH3NO2, (c) 1.68 kg RDX, C3H6N6O6.3.50 A test of an automobile engine's exhaust revealed that g of NO2 was emitted in 10 minutes of operation. How many moles of NO2 would this engine release if it were used for a 45-minute commute, assuming that this mea- sured number is representative of the emission under all circumstances?3.51 Modern instruments can measure a mass as small as 5 nano- grams. If one observed 5.0 ng of CO2, how many molecules were measured?3.52 How many H atoms are present in 7.52 g of propane, C3H8?3.53 How many O atoms are present in 214 g of mannose (C6H12O6)?A sample of H2C2O4.2H2O of mass 3.35 g is heated to drive off the waters of hydration (designated separately in the chemical formula). What mass of H2C2O4 remains once the water has been removed by heating?3.55 An average person inhales roughly 2.5 g of O2 in a minute. How many molecules of oxygen are inhaled in (a) 1 minute, (b) 1 hour, (c) 1 day by an average person?3.56 A large family of boron-hydrogen compounds has the general formula BxHy. One member of this family contains 88.5% B; the remainder is hydrogen. What is its empirical formula?3.57PAE 3.58 Determine the simplest formulas of the following compounds. (a) the food enhancer monosodium glutamate (MSG), which has the composition 35.51% C, 4.77% H, 37.85% O, 8.29% N, and 13.60% Na; (b) zircon, a diamond-like min- eral, which has the composition 34.91% O, 15.32% Si, and 49.76% Zr; (c) nicotine, which has the composition 74.0% C, 8.65% H, and 17.4% N 3.59 The composition of materials such as alloys can be described in terms of mole percentage (mol%), atom percentage (at%), or weight percentage (wt%). Carry out the following conversions among these units. (a) 60 Cu and 40 Al to at%, (b) 25 mol% NiO and 75 mol % MgO to wt%, (C) 40 wt% MgO and 60 wt% Feo to mol %3.60 Copper can have improved wear resistance if alloyed with ceramic alumina, A12O3. If a copper alloy has 8.5 wt% A12O3, what is its composition in mol%?3.61 Calculate the molarity of each of the following solutions. (a) 1.45 mol HCl in 250. mL of solution (b) 14.3 mol NaOH in 3.4 L of solution (c) 0.341 mol KCl in 100.0 mL of solution (d) 250 mol NaNO3 in 350 L of solution 3.62 What is the molarity of each ion present in aqueous solutions prepared by dissolving 20.00 g of the following compounds in water to make 4.50 L of solution? (a) cobalt(III) chloride, (b) nickel(III) sulfate, (c) sodium permanganate, (d) iron(II) bromide 3.63 How many moles of solute are present in each of these solutions? (a) 48.0 mL of 3.4 M H2SO4. (b) 1.43 mL of 5.8 M KNO3. (c) 321 L of 0.034M NH3 (d) 1.9 × 10-3 L of 1.4 × 10-5 M NaF 3.64 How many grams of solute are present in each of these solutions? (a) 37.2 mL ofO.471 M HBr (b) 113.0 L of 1.43 M Na2CO3 (c) 212 mL of 6.8 M CH3COOH (d) 1.3 × 10-4 L of 1.03 M H2S03 3.65 Determine the final molarity for the following dilutions. (a) 24.5 mL of 3.0 M solution diluted to 100.0 mL (b) 15.3 mL of 4.22 M solution diluted to 1.00 L (c) 1.45 mL of 0.034 M solution diluted to 10.0 mL (d) 2.35 L of 12.5 M solution diluted to 100.0 L 3.66PAE 3.67PAE 3.68 Magnesium is lighter than other structural metals, so it is increasingly important in the design of more efficient vehicles. Mg2+ ions are present in seawater, and the metal is often prepared by "harvesting" these ions and converting them to Mg metal. The average magnesium content of the oceans is about 1270 g Mg2+ per ton of seawater, and the density of seawater is about 1.03 g/mL. What is the molarity of Mg2+ ions in seawater? The design for a concept car calls for 103 kg of magnesium per vehicle. How many gallons of seawater would be required to supply enough magnesium to build one of these ears?3.69PAE 3.70PAE 3.71 What is meant by the term carbon reservoir? What are the two largest carbon reservoirs for our planet?3.72PAE 3.73PAE 3.74PAE 3.75 The following pictures show a molecular-scale view of a chemical reaction between the compounds AB2 and B2. (A atoms are shown in blue and B atoms in white). The box on the left represents the reactants at the instant of mixing, and the box on the right shows what is left once the reac- tion has gone to completion. Write a balanced chemical equation for this reaction. As usual, your equation should use the smallest possible whole number coefficients for all substances.3.76PAE 3.77 Answer each of the following questions. Note that none of them should require difficult calculations. (a) How many molecules are present in 1 mole of octane (C4H18)? (b) How many moles of fluorine atoms are present in 4 moles of C2F6? (c) What is the approximate mass (to the nearest gram) of 3 × 1023 carbon atoms?3.78 Consider two samples of liquid: I mole of water (H2O) and 1 mole of ethanol. Answer each of the following questions. Note that none of these should require significant calculations. (a) Which sample contains more atoms? (b) Which sample contains more molecules? (c) Which sample has a larger mass?3.79 Consider two samples. Sample A contains 2 moles of N2 and 1 mole of O2, and Sample B contains 1 mole of N2O5. (a) Which sample contains more molecules? (b) Which sample contains more oxygen atoms? (c) Which sample contains more nitrogen atoms?3.80 Which one of the following metal samples cannot possibly exist? not? (a) a piece of gold foil 10-6 m thick (b) 5 mg of platinum (c) 10-24 mol of aluminum (d) a copper wire 0.1 mm in diameter

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