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All Textbook Solutions for Chemistry for Engineering Students

3.81 The particulate scale drawing shown depicts the products of a reaction between H2 and O2 molecules. (a) Draw a similar representation for the reactants that must have been present before the reaction took place. (b) Write a balanced chemical equation for the reaction, using the smallest possible whole number coefficients.3.82 The particulate scale drawing shown depicts the products of a reaction between N2 and O2 molecules. (a) Draw a similar representation for the reactants that must have been present before the reaction took place. (b) Write a balanced chemical equation for the reaction, using the smallest possible whole number coefficients.3.83 For the reaction of nitrogen, N2, and hydrogen, H2, to form ammonia, NH3, a student is attempting to draw a particulate diagram, as shown below. Did the student draw a correct representation of the reaction? If not, what was the error the student made?3.84 The picture shown depicts the species present at the start of a combustion reaction between methane, CH4, and oxygen, O2. (a) Draw the resulting state after this set of re- actants has reacted as far as possible. (b) Use the drawings to explain the stoichiometry represented in the balanced chemical equation for the combustion of methane.3.85 The particulate drawing shown represents an aqueous so- lution of an acid HA, where A might represent an atom or group of atoms. Is HA a strong acid or a weak acid? Explain how you can tell from the picture.3.86 When a solution is diluted, solvent is added but solute is not. Explain how this idea leads to the equation frequently used in dilution calculations, M1V1= M2V2.3.87 Nitric acid (HNO3) can be produced by the reaction of ni- trogen dioxide (NO2) and water. Nitric oxide (NO) is also formed as a product. Write a balanced chemical equation for this reaction.3.88 One Step in the enrichment of uranium for use in nuclear power plants involves the reaction of UO2 with hydro- fluoric acid (HF) solution. The products are solid UF4 and water. Write a balanced chemical equation for this reaction.3.89 Pyridine has the molecular formula C5H5N. When pyri- dine reacts with O2, the products are CO2, H2O, and N2. Write a balanced equation for this reaction.3.90 Pyrrole has the molecular formula C4H5N. When pyrrole reacts with O2, the products are CO2, H2O, and N2. Write a balanced equation for this reaction.3.91 Hydrogen cyanide (HCN) is extremely toxic, but it is used in the production of several important plastics. In the most common method for producing HCN, ammonia (NH3) and methane (CH4) react with oxygen (O2) to give HCN and water. Write a balanced chemical equation for this reaction. Hydrogen cyanide, HCN 3.92 Many chemical reactions take place in the catalytic con- verter of a car. In one of these reactions, nitric oxide (NO) reacts with ammonia (NH3) to give nitrogen (N2) and water. Write a balanced equation for this reaction.3.93 Adipic acid is used in the production of nylon, so it is manufactured in large quantities. The most common method for the preparation of adipic acid is the reaction of cyclohexane with oxygen. Balance the skeleton equation shown be1ow.3.94 Calcium carbonate (limestone, CaCO3) dissolves in hydrochloric acid, producing water and carbon dioxide. An unbalanced net ionic equation for this reaction is given below. Balance it. CaCO3(s)+H3O+(aq)H2O(l)+CO2(g)+Ca2+(aq)3.95 Cumene is a hydrocarbon, meaning that it contains only carbon and hydrogen. If this compound is 89.94% C by mass and its molar mass is 120.2 g/mol, what is its molecular formula?3.96 Methyl cyanoacrylate is the chemical name for the substance sold as Super Glue, and it has the chemical formula C5H5NO2. Calculate the number of molecules of this substance in a 1.0-ounce tube of Super Glue, assuming that the glue is 80% methyl cyanoacrylate by mass.3.97 A low-grade form of iron ore is called taconite, and the iron in the ore is in the form Fe3O4. If a 2.0-ton sample of taconite pellets yields 1075 pounds of iron when it is refined, what is the mass percentage of Fe3O4in taconite?3.98 The characteristic odor of decaying flesh is due to the presence of various nitrogen-containing compounds. One such compound, called putrescine, was analyzed and found to contain 54.49% carbon, 13.72% hydrogen, and 31.78% nitrogen by mass. If the molar mass of putrescine is known to be between 85 and 105, what is its molecular formula?3.99 Iron—platinum alloys may be useful as high-density recording materials because of their magnetic properties. These alloys have been made with a wide range of composition, from 34.0 at% Pt to 81.8 at% Pt. Express this range in mol%.3.100 Some aluminum—lithium alloys display the property of superplasticity, meaning they can undergo tensile deformation by large amounts (1000 times or more) without breaking. If such an alloy has 4 wt% Li, what is its composition in mol%? Explain the relative magnitudes of the mole percentage and weight percentage based on the molar masses of aluminum and lithium.3.101 Which (if any) of the following compounds are electrolytes? (a) glucose, C6H12O6, (b) ethanol, C2H5OH, (c) magnesium sulfide, MgS, (d) sulfur hexafluoride, SF6 3.102 Classify the following compounds as acids or bases, weak or strong. (a) perchloric acid, (b) cesium hydroxide, (c) carbonic acid, H2CO3, (d) ethylamine, C2H5NH2 3.103 What is the mass in grams of solute in 250.0 mL of a 0.0125 M solution of KMnO4?3.104 What volume of 0.123 M NaOH in milliliters contains 25.0 g NaOH?3.105 Nitric acid is often sold and transported as a concentrated 16 M aqueous solution. How many gallons of such a solution would be needed to contain the roughly 2.1109 pounds of HNO3 produced annually in the United States?3.106 Twenty-five mL of a 0.388 M solution of Na2SO4 is mixed with 35.3 mL of 0.229 M Na2SO4. What is the molarity of the resulting solution? Assume that the volumes are additive.3.107 As computer processor speeds increase, it is necessary for engineers to increase the number of circuit elements packed into a given area. Individual circuit elements are often connected using very small copper “wires” deposited directly onto the surface of the chip. In some processors, these copper interconnects are about 22 nm wide. How many copper atoms would be in a 1-mm length of such an interconnect, assuming a square cross section? (The density of copper is 8.96 g/cm3.)3.108 As chip speeds increase, the width of the interconnects described in Problem 3.107 must be reduced. A hypothetical limit to this process would be reached if the interconnect was just one copper atom wide. Use the density of copper (8.96 g/cm3) to estimate the diameter of a copper atom. (Optical interconnects are being developed, and are likely to replace copper in this application within a few years.)3.109 Materials engineers often create new alloys in an effort to improve the properties of an existing material. ZnO based semiconductors show promise in applications like light-emitting diodes, but their performance can be enhanced by the addition of small amounts of cadmium. One material that has been studied can he represented by the formula Zn0.843Cd0.157O. (These materials are solid solutions, and so they can have variable compositions. The noninteger coefficients do not imply fractional atoms.) Express the composition of this alloy in terms of (a) at%, (b) mol%, and (c) wt%.3.110 The protein that carries oxygen in the blood is called hemoglobin. It is 0.335% Fe by mass. Given that a molecule of hemoglobin contains four iron atoms, describe how you can calculate the molar mass of hemoglobin. Do you need to look up anything to do it?3.111 The chlorophyll molecule responsible for photosynthesis in plants contains 2.72% Mg by mass. There is only one Mg atom per chlorophyll molecule. How can you determine the molar mass of chlorophyll based on this information?3.112 In one experiment, the burning of 0.614 g of sulfur produced 1.246 g of sulfur dioxide as its only product. In a second experiment run to verify the outcome of the first, a sample was burned and 0.813 g of sulfur dioxide was obtained, but the student running the experiment forgot to determine the initial mass of sulfur burned. Describe how the data already obtained could be used to calculate the initial mass of the sulfur burned in the second experiment.3.113 MgCl2 is often found as an impurity in table salt (NaCl). If a 0.05200-g sample of table salt is found to contain 61.10% Cl by mass, describe how you could determine the percentage of MgCl2 in the sample.3.114PAE 3.115 The average person exhales 1.0 kg of carbon dioxide in a day. Describe how you would estimate the number of CO2 molecules exhaled per breath for this average person.3.116 The simplest approximate chemical formula for the human body could be written as C728H4850O1970N104Ca24P16K4S4Na3Cl2Mg. Based on this formula, describe how you would rank by mass the ten most abundant elements in the human body.3.117 For the oxides of iron, FeO, Fe2O3, and Fe3O4, describe how you would determine which has the greatest percentage by mass of oxygen. Would you need to look up any information to solve this problem?3.118 Consider common sugars such as glucose (C6H12O6) and sucrose (C12H22O11). What type of chemical bonding would you expect to find in these chemicals?3.119PAE 3.120 1f you have 32.6 g of sodium carbonate that is dissolved to give 2.10 L of solution, what is the molarity of the solution? What is the molarity of the sodium ions?3.121 If you have 21.1 g of iron(II) nitrate that is dissolved to give 1.54 L of solution, what is the molarity of the solution? What is the molarity of the nitrate ions?3.122 What type of reasoning were we using when we developed the equation for dilution, MiVi=MfVf ?3.123 Most periodic tables provide molar masses with four or five significant figures for the elements. How accurately would you have to measure the mass of a sample of roughly 100 g to make a calculation of the number of moles of the chemical to have its significant figures limited by the molar mass calculation rather than the mass measurement?Describe the chemical composition of gasoline.Write balanced chemical equations for the combustion of fuels.3CO Calculate the amounts of reactants needed in a chemical reaction to produce a specified amount of product.5CO 6CO 7CO 4.1 List at least two factors that make it difficult to describe the combustion of gasoline accurately. What assumption can be made to address these complications?4.2 What is an alkane?4.3 Explain the difference between complete and incomplete combustion.4.4 Automobile exhaust often contains traces of formaldehyde (CH2O), which is another possible product of incomplete combustion. Write a balanced equation for the formation of formaldehyde during the combustion of octane. (Water will also be formed as a product.)4.5 Methane, ethane, and propane are also hydrocarbons, but they are not major components of gasoline. What prevents them from being part of this mixture?4.6 Use the web to research prices of gasoline at the pump for consumers in your area during the past year. Also find information about the price of crude oil for the same period. Discuss any correlations you observe between the two prices.For the following reactions, write the ratios that can be established among molar amounts of the various compounds. 2H2+O22H2O 2H2O22H2O+O2 P4+5O2P4O10 2KClO32KCl+3O2 xs 4.8 In an experiment carried out at very low pressure, 13x1015 molecules of H2 are reacted with acetylene, C2H2, to form ethane, C2H6, on the surface of a catalyst. Write a balanced chemical equation for this reaction. How many molecules of acetylene are consumed?4.9 Sulfur, S8, combines with oxygen at elevated temperatures to form sulfur dioxide. (a) Write a balanced chemical equation for this reaction. (b) If 200 oxygen molecules are used up in this reaction, how many sulfur molecules react? (c) How many sulfur dioxide molecules are formed in part (b)?4.10 How many moles of oxygen can be obtained by the decomposition of 7.5 mol of reactant in each of the following reactions? 2KClO32KCl+3O2 2H2O22H2O+O2 2HgO2Hg+O2 2NaNO32NaNO2+O2 KClO4KCl+2O2 4.11 MTBE, C5H12O, is one of the additives that replaced tetraethyl-lead in gasoline. (See Example Problem 4.6 and Section 4.6.) How many moles of O2 are needed for the complete combustion of 1.50 mol of MTBE?4.12 In petroleum refining, hydrocarbons are often manipulated by reacting them with H2(g). If hexene, C6H12, is reacted with hydrogen to form hexane, C6H14, how many moles of hydrogen are needed to react with 453 moles of hexene?4.13 For the following reactions, determine the value of x. 4C+S84CS2 mol S8 yields x mol CS2 CS2+3O2CO2+2SO2 mol CS2 yields x mol SO2 N2H4+3O22NO2+2H2O mol O2 yields x mol NO2 SiH4+2O2SiO2+2H2O 1.3103 mol SiH4 yields x mol H2O 4.14 The combustion of liquid chloroethylene, C2H3Cl, yields carbon dioxide, steam, and hydrogen chloride gas. (a) Write a balanced equation for the reaction. (b) How many moles of oxygen are required to react with 35.00 g of chloroethylene? (c) If 125.00 g of chloroethylene reacts with an excess of oxygen, how many grams of each product are formed?4.15 What mass of the unknown compound is formed in the following reactions? (Assume that reactants for which amounts are not given are present in excess.) C2H4+H2C2H6 g C2H4 reacts to produce x g C2H6 CS2+3Cl2CCl4+S2Cl2 5.78 g Cl2 reacts to produce x g S2CL2 PCl3+3H2OH3PO3+3HCl mg PCl3 reacts to produce x mg HCl B2H6+O2B2O3+3H2O kg B2H6 reacts to produce x kg B2O3 4.16 Many metals react with halogens to give metal halides. For example, iron reacts with chlorine to give iron(II) chloride, FeCl2: Fe(s)+Cl2(g)FeCl2(s) Beginning with 10.0 g iron, what mass of Cl2, in grams, is required for complete reaction? What quantity of FeCl2, in motes and in grams, is expected?4.17 Phosgene is a highly toxic gas that has been used as a chemical weapon at times in the past. It is now used in the manufacture of polycarbonates, which are used to make phone cases and plastic eyeglass lenses. Phosgene is produced by the reaction, CO+Cl2COCl2 . Given an excess of carbon monoxide, what mass of chlorine gas must be reacted to form 4.5 g of phosgene?4.18PAE 4.19 How many metric tons of carbon are required to react with 7.83 metric tons of Fe2O3 according to the following reaction? 2Fe2O3+3C3CO2+4Fe How many metric tons of iron are produced?4.20 Assuming a charcoal briquette is composed entirely of carbon, what mass of oxygen is needed to completely burn a 37.3-g briquette?4.21 Ammonium nitrate, NH4NO3, will decompose explosively to form N2, O2, and H2O, a fact that has been exploited in terrorist bombings. What mass of nitrogen is formed by the decomposition of 2.6 kg of ammonium nitrate?4.22 Generally, an excess of O2 is needed for the reaction Sn+O2SnO2 . What is the minimum number of moles of oxygen required to oxidize 7.3 moles of tin?4.23 In the reaction of arsenic with bromine, AsBr5 will form only when excess bromine is present. Write a balanced chemical equation for this reaction. Determine the minimum number of motes of bromine that are needed if 9.6 moles of arsenic is present.4.24 Ammonia gas can be prepared by the reaction CaO(s)+2NH4Cl(s)2NH3(g)+H2O(g)+CaCl2(s) If 112 g of CaO reacts with 224 g of NH4Cl, how many moles of reactants and products are there when the reaction is complete?4.25 When octane is combusted with inadequate oxygen, carbon monoxide may form. If 100 g of octane is burned in 200 g of O2, are conditions conductive to forming carbon monoxide?4.26 The equation for one of the reactions in the process of turning iron ore into the metal is Fe2O3(s)+3CO(g)2Fe(s)+3CO2(g) If you start with 2.00 kg of each reactant, what is the maximum mass of iron you can produce?4.27 Copper reacts with sulfuric acid according to the following equation: 2H2SO4+CuCuSO4+2H2O+SO2 How many grams of sulfur dioxide are created by this reaction if 14.2 g of copper reacts with 18.0 g of sulfuric acid?4.28 One of the steps in the manufacture of nitric acid is the oxidation of ammonia shown in this equation: 4NH3(g)+5O2(g)4NO(g)+6H2O(g) If 43.0 kg of NH3 reacts with 35.4 kg of O2, what mass of NO forms?4.29 When Al(OH)3 reacts with sulfuric acid, the following reaction occurs: 2Al(OH)3+3H2SO4Al2( SO4)3+6H2O If 1.7103 g of Al(OH)3 is combined with 680 g of H2SO4, how much aluminum sulfate can form?4.30 Copper reacts with nitric acid via the following equation: 3Cu(s)+8HNO3(aq)3Cu( NO3)2(aq)+2NO(g)+4H2O(l) What mass of NO(g) can be formed when 10.0 g of Cu reacts with 115 g of HNO3?4.31 How much HNO3 can be formed in the following reaction if 3.6 kg of NO2 gas is bubbled through 2.5 kg of water? 3NO2(g)+H2O(l)2HNO3(aq)+NO(g)4.32 Hydrogen and oxygen are reacted and the water formed is collected at 25°C, where it has a density of 0.997 g/mL. If 36.8 g of H2 and 168 g of O2 are reacted, how many mL of water will be collected?4.33 Silicon carbide, an abrasive, is made by the reaction of silicon dioxide with graphite (solid carbon): SiO2+CSiC+CO(balanced?) We mix 150.0 g of SiO2 and 101.5 g of C. If the reaction proceeds as far as possible, which reactant is left over? How much of this reactant remains?4.34PAE 4.35PAE 4.36 Sometimes students in chemistry labs determine percentage yields greater than 100%. Assuming there is no calculation error, how could this happen?4.37 The theoretical yield and the actual yield for various reactions are given below. Determine the corresponding percentage yields. Theoretical Yield Actual Yield Reaction 1 35.0 g 12.8 g Reaction 2 9.3 g 120 mg Reaction 3 3.7 metric tons 1250 kg Reaction 4 40.0 g 41.0 g 4.38 A reaction that produced 4.8 mg of taxol, an anticancer drug, is reported to have a yield of 38%. What was the theoretical yield?Methanol, CH3OH, is used in racing cars because it is a clean-burning fuel. It can be made by this reaction: CO(g)+2H2(g)CH3OH(l) What is the percentage yield if 5.0103gH2 reacts with excess CO to form 3.5104gCH3OH ?4.40 When iron and steam react at high temperatures, the following reaction takes place: 3Fe(s)+4H2O(g)Fe3O4(s)+4H2(g) How much iron must react with excess steam to form 897 g of Fe3O4 if the reaction yield is 69%?4.41 The percentage yield of the following reaction is consistently 87%. CH4(g)+4S(g)CS2(g)+2H2S(g) How many grams of sulfur would be needed to obtain 80.0 g of CS2?4.42 Sulfur hexafluoride is a very stable gas useful ¡n electrical generators and switches. It is formed by direct synthesis from the elements: S(s)+3F2(g)SF6(g) If 92 g of SF6 is produced from the reaction of 115 g of sulfur ¡n excess fluorine, what is the percentage yield? Sulfur hexafluoride, SF6 4.43 Magnesium nitride forms in a side reaction when magnesium metal burns in air. This reaction may also be carried out in pure nitrogen. 3Mg(s)+N2(g)Mg3N2(s) If 18.4 g of Mg3N2forms from the reaction of 20.0 g of magnesium with excess nitrogen, what is the percentage yield?4.44 Industrial production of hydrogen gas uses the reaction shown below. If 1.00 metric ton of propane reacting with excess water yields 270 kg of H2, what is the percentage yield? C3H8(g)+3H2O(l)3CO(g)+7H2(g)4.45 If 21 g of H2S is mixed with 38 g of O2 and 31 g of SO2 forms, what is the percentage yield? 2H2S+3O22SO2+2H2O 4.46 A mixture of 10.0 g of NO and 14.0 g of NO2 result in the production of 8.52 g of N2O3. What is the percentage yield? NO(g)+NO2(g)N2O3(l)4.47 Silicon carbide is, an abrasive used in the manufacture of grinding wheels. A company is investigating whether they can be more efficient in the construction of such wheels by making their own SiC via the reaction SiO2+3CSiC+2CO (a) If this reaction consistently has a yield of 85%, what is the minimum amount of both silicon dioxide and carbon needed to produce 3400 kg of SiC for the manufacture of cutting wheels? (b) The silicon dioxide is to he obtained from sand and the carbon is derived from coal. If the available sand is 95% SiO2 by weight and the coal is 73% C by weight, what mass of coal is needed for each metric ton of sand used?4.48 Elemental phosphorous is used in the semiconductor industry. It can be obtained from an ore called fluoroapatite via reaction with SiO2 and C: 4Ca5( PO4)3F+18SiO2+30C3P4+30CO+18CaSiO3+2CaF2 Suppose a particular semiconductor production plant requires 1500 kg of P4. If the recovery of P4 from this reaction is 73% efficient, what mass of fluoroapatite is needed?4.49 Small quantities of hydrogen gas can be prepared by the following reaction: Zn(s)+H2SO4(aq)ZnSO4(aq)+H2(g) How many grams of H2 can be prepared from 25.0 mL of 6.00 M H2SO4 and excess zinc?4.50PAE 4.51 What is the role of an indicator in a titration?4.52 What volume of 0.812 M HCl, in milliliters, is required to titrate 1.45 g of NaOH to the equivalence point? NaOH(aq)+HCl(aq)H2O(l)+NaCl(aq)4.53PAE 4.54PAE Hydrazine, N2H4, is a weak base and can react with an acid such as sulfuric acid: 2N2H4(aq)+H2SO4(aq)2N2H5+(aq)+SO42(aq) What mass of hydrazine can react with 250. mL 0.225 M H2SO4?4.56PAE 4.57PAE 4.58PAE 4.59 Aluminum dissolves in HCI according to the equation written below, whereas copper does not react with HCl. 2Al( s )+6HCl( aq ) 2AlCl 3 ( aq )+ 3H 2 ( g ) A 35.0-g sample of a copper—aluminum alloy is dropped into 750 mL of 3.00 M HCl, and the reaction above proceeds as far as possible. If the ahoy contains 77.1% Al by mass, what mass of hydrogen gas would be produced?4.60 Why are fuel additives used?4.61 What is actually measured by the octane ratings of different grades of gasoline?4.62PAE 4.63PAE 4.64 Using the web, find information about the amount of lead in the environment during the past 50 years. Correlate what you observe with the presence or absence of tetraethyl lead in gasoline.4.65 Using the web, find out how lead “poisons” the catalyst in a catalytic converter.4.66 If 3.4 mol Al is mixed with 1.5 times as many moles of Fe2O3, what is the limiting reactant? 2Al+Fe2O3Al2O3+2Fe 4.67 If 8.4 moles of disilane, Si2H6, are combined with 3 times as many moles of O2, which is the limiting reactant? 2Si2H6+7O24SiO2+6H2O 4.68 The pictures below show a molecular-scale view of a chemical reaction between the compounds AB2 and B2. (Green balls represent B atoms and orange balls are A atoms). 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 reaction has gone to completion. Was there a limiting reactant in this reaction? If so, what was it? Write a balanced chemical equation for this reaction. As usual, your equation should use the smallest possible whole number coefficients for all substances.4.69 The pictures below show a molecular-scale view of a chemical reaction between H2 and CO to produce methanol, CH3OH. 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 reaction has gone to completion. Was there a limiting reactant in this reaction? If so, what was it? Write a balanced chemical equation for this reaction. As usual, your equation should use the smallest possible whole number coefficients for all substances.4.70 The particulate scale drawing shown depicts the products of a reaction between H2 and O2 molecules. (a) Draw a similar representation for the reactants that must have been present before the reaction took place. (b) Write a balanced chemical equation for the reaction, using the smallest possible whole number coefficients. (c) identify the limiting reactant, and explain how the pictures allow you to do so.4.71 The particulate scale drawing shown depict the products of a reaction between N2 and O2 molecules. (a) Draw a similar representation for the reactants that must have been present before the reaction took place. (b) Write a balanced chemical equation for the reaction, using the smallest possible whole number coefficients. (c) Identify the limiting reactant, and explain how the pictures allow you to do so.4.72 The picture shown depicts the species present at the start of a combustion reaction between methane, CH4 and oxygen, O2 (a) What is the limiting reactant? (b) Draw the resulting state after this set of reactants has reacted as far as possible.4.73PAE 4.74PAE 4.75PAE 4.76PAE You have 0.954 g of an unknown acid, H2A, which reacts with NaOH according to the balanced equation H2A(aq)+2NaOH(aq)Na2A(aq)+2H2O(l) If 36.04 mL of 0.509 M NaOH is required to titrate the acid to the equivalence point, what is the molar mass of the acid?4.78PAE 4.79 Phosphoric add (H3PO4) is important in the production of both fertilizers and detergents. It is distributed commercially as a solution with a concentration of about 14.8 M. Approximately 2.1 X l09 gallons of this concentrated phosphoric acid solution is produced annually in the United States. Assuming that all of this H3PO4 is produced by the reaction below, what mass of the mineral fluoruapatite (Ca5(PO4)3F) would be required each year? Ca5( PO4)3F+5H2SO43H3PO4+5CaSO4+HF 4.80 The reaction shown below is used to destroy Freon-12 (CF2Cl2), preventing its release into the atmosphere. What mass of NaF will be formed if 250.0 kg of CF2Cl2 and 400.0 kg of Na2C2O4 are heated and allowed to react to completion? CF2Cl2+2Na2C2O42NaF+2NaCl+C+4CO2 4.81PAE One way of determining blood alcohol levels is by performing a titration on a sample of blood. In this process, the alcohol from the blood is oxidized by dichromate ions (Cr2O72-) according to the following net ionic equation: C2H5OH+2Cr2O72+16H+2CO2+4Cr3++11H2O A 10.00-g sample of blood was drawn from a patient, and 13.77 mL of 0.02538 M K2Cr2O7 was required to titrate the alcohol. What was the patient’s blood alcohol level? (See the previous problem for definition of blood alcohol level. K2Cr2O7 is a strong electrolyte, so it dissociates completely in solution.)4.83PAE 4.84 Aluminum chloride (AlCl3) is used as a catalyst in the production of polyisobutylene, which is used in automobile tires. Scrap aluminum metal reacts with chlorine gas (Cl2) to produce AlCl3. Suppose that 2.70 g of Al and 7.10 g of Cl2 are mixed. What is the maximum mass of AlCl3 that could be formed?4.85 In the cold vulcanization of rubber, disulfur dichloride (S2Cl2) is used as a source of sulfur atoms, and those sulfur atoms form “bridges,” or cross-links, between polymer chains. S2Cl2 can be produced by reacting molten sulfur (S8(l)) with chlorine (Cl2(g)). What is the maximum mass of S2Cl2 that can be produced by reacting 32.0 g of sulfur with 71.0 g of chlorine?4.86PAE 4.87PAE 4.88 A quality control technician needs to determine the percentage of arsenic (As) in a particular pesticide. The pesticide is dissolved and all of the arsenic present is converted to arsenate ions (AsO43-). Then the amount of AsO43- is determined by titrating with a solution containing silver ions (Ag+). The silver reacts with the arsenate according to the following net ionic equation: 3Ag+(aq)+AsO43(aq)Ag3AsO4(s) When a 1.22-g sample of pesticide was analyzed this way, it required 25.0 mL of 0.102 M Ag+ solution to precipitate all of the AsO43-. What was the mass percentage of arsenic in the pesticide?4.89PAE 4.90 Iron metal can be refined (rom the mineral hematite (Fe2O3). One way of converting the mineral to iron is to react it with carbon monoxide, as shown below: Fe2O3+3CO2Fe+3CO2 Because the hematite is obtained from various ores, it is usually not in a pure form. Suppose an iron manufacturer has 2.00 X 105 kg of ore available, and the ore is 93% Fe2O3 by mass. (There is no iron in the remaining 7% of the ore.) How many moles of Fe2O3are present in this ore? How many kg of pure iron could be obtained from this sample of ore? Assume that the process has a 100% yield and that excess CO is available.4.91PAE 4.92PAE 4.93 A mixture of methane (CH4) and propane (C3H8) has a total mass of 29.84 g. When the mixture is burned completely in excess oxygen, the CO2 and H2O products have a combined mass of 142.97 g. Calculate the mass of methane in the original mixture.4.94PAE 4.95PAE 4.96PAE 4.97PAE 4.98PAE 4.99PAE 4.100PAE 4.101PAE 4.102PAE 4.103PAE 4.104 When 2.750 g of the oxide Pb3O4 is heated to a high temperature, it decomposes to produce 0.0640 g of oxygen gas and 2.686 g of some new lead oxide compound. How can you use these data to determine the formula of the new compound?4.105PAE 4.106 An ore sample with a mass of 670 kg contains 27.7% magnesium carbonate, MgCO3. If all of the magnesium carbonate in this ore sample is decomposed to form carbon dioxide, describe how to determine what mass of CO2 is evolved during the process.4.107 Existing stockpiles of the refrigerant Freon-12, CF2Cl2 must be destroyed under the terms of the Montreal Protocol because of their potential for banning the ozone layer. One method for doing this involves reaction with sodium oxalate: CF 2 Cl 2 + 2Na 2 C 2 O 4 2NaF+2NaCl+C+ 4CO 2 S If you had 150 tons of Freon-12, describe how you would know how much sodium oxalate you would need to make that conversion. Freon-12, CF2Cl2 4.108 Elemental analysis is sometimes carried out by combustion of the sample. For a hydrocarbon, the only products formed are CO2 and H2O. If a 1.36-g sample of an unknown hydrocarbon is burned and 2.21 g of H2O is produced along with 4.07 g of CO2, what is the empirical formula of the hydrocarbon?4.109PAE 4.110 Write the balanced chemical equation lot the combustion of ethane, C2H6, and answer these questions. (a) How many molecules of oxygen would combine with 14 molecules of ethane in this reaction? (b) If 13.0 mol of oxygen is consumed in a reaction, how many moles of water are produced? (e) How many grams of ethane are burned if 4.201022 molecules of CO2 are produced?4.111 Aluminum metal reacts with sulfuric acid to form hydrogen gas and aluminum sulfate (a) Write a balanced chemical equation for this reaction. (b) Suppose that a 0.792-g sample of aluminum that contains impurities is reacted with excess sulfuric acid and 0.0813 g of H2 is collected. Assuming that none of the impurities reacts with sulfuric acid to produce hydrogen, what is the percentage of aluminum in the sample?4.112 A metallurgical firm wishes to dispose of 1300 gallons of waste sulfuric acid whose molarity is 1.37 M. Before disposal, it will be reacted with calcium hydroxide (slaked lime), which costs $0.23 per pound. (a) Write the balanced chemical equation for this process. (b) Determine the cost that the firm will incur from this use of slaked lime.1CO 2CO 3CO 4CO perform stoichiometric ca1cu1uions for reactions involving gases as reactants or products.6CO 7CO 8CO 9CO 10CO 11CO 5.1PAE 5.2PAE What possible uses exist for the natural gas liquids that are removed from natural gas during its processing?How does hydraulic fracturing differ from previously used techniques for the recovery of natural gas from the earth?5.5PAE Use the internet to determine what areas of the United States have made the widest use of hydraulic fracturing. Is the current production of natural gas from these areas smaller, greater, or about the same as it was 5 years ago?5.7PAE 5.8PAE 5.9PAE 5.10PAE 5.11PAE 5.12 Water has a density that is 13.6 times less that of mercury. How high would a column of water need to be to measure a pressure of 1 atm?5.13 Water has a density that is 13.6 times less that of mercury. If an undersea vessel descends to 1.5 km, how much pressure does the water exert in atm?5.14PAE 5.15 Gas pressure can be expressed in units of mm Hg, atm, torr, and kPa. Convert these pressure values. (a) 722 mm Hg to atm, (b) 1.25 atm to mm Hg, (c) 542 mm Hg to torr, (d) 745 mm Hg to kPa, (e) 708 kPa to atm 5.16 If the atmospheric pressure is 97.4 kPa, how much is it in mm Hg? In atm?5.17PAE 5.18 When helium escapes from a balloon, the balloon’s volume decreases. Based on your intuition about stretching rubber, explain how this observation is consistent with the gas law.5.19 A sample of CO2 gas has a pressure of 56.5 mm Hg in a 125-mL flask. The sample is transferred to a new flask, where it has a pressure of 62.3 mm Hg at the same temperature. What is the volume of the new flask?5.20PAE 5.21PAE 5.22PAE 5.23 A gas bubble forms inside a vat containing a hot liquid. If the bubble is originally at 68°C and a pressure of 1.6 atm with a volume of 5.8 mL, what will its volume be if the pressure drops to 12 atm and the temperature drops to 31°C?5.24 A bicycle tire is inflated to a pressure of 3.74 atm at 15°C. If the tire is heated to 35°C, what is the pressure in the tire? Assume the tire volume doesn’t change.5.25 A balloon filled with helium has a volume of 1.28103 L at sea level where the pressure is 0.998 atm and the temperature is 31°C. The balloon is taken to the top of a mountain where the pressure is 0.753 atm and the temperature is 25C . What is the volume of the balloon at the top of the mountain?5.26 How many moles of an ideal gas are there if the volume of the gas is 158 L at 14°C and a pressure of 89 kPa?5.27 A newly discovered gas has a density of 2.39 g/L at 23.0°C and 715 mm Hg. What is the molar mass of the gas?5.28 Calculate the mass of each of the following gases at STP: (a) 1.4 L of SO2. (b) 3.5105 L of CO2 5.29 What are the densities of the following gases at STP? (a) CF2Cl2, (b)CO2, (c) HCl 5.30PAE 5.31 A cylinder is filled with toxic COS gas to a pressure of 800.0 torr at 24°C. According to the manufacturer’s specifications, the cylinder may rupture if the pressure exceeds 35 psi (pounds per square inch; 1 atm = 14.7 psi). What is the maximum temperature to which the cylinder could be heated without exceeding this pressure rating?5.32 Cylinders of compressed gases are often labeled to show how many “SCF” or “standard cubic feet” of gas they contain. 1 SCF of gas occupies a volume of 1 ft3 at a standard temperature and pressure of 0°C and 1 atm. A particular cylinder weighs 122 lb. when empty and 155 lb. when filled with krypton gas at 26°C. How many SCF of Kr does this cylinder contain?5.33PAE 5.34 Define the term mole fraction 5.35PAE 36 What is the total pressure exerted by a mixture of 1.50 g of H2 and 5.00 g of N2 in a 5.00-L vessel at 25°C?5.37PAE 38 For a gas sample whose total pressure is 740 torr, what are the partial pressures if the gas present consists of 1.3 mol of N2, 0.33 mol of O2, and 0.061 moI of Ar?39 A sample containing only NO2 and SO2, has a total pressure of 120. torr. Measurements show that the partial pressure of NO2 is 43 torr. 1f the vessel has a volume of 800.0 mL and the temperature is 22.0°C, how many moles of each gas are present?5.40PAE 41 A sample of a smokestack emission was collected into 1.25-L tank at Hg and analyzed. The analysis showed 92% CO2, 3.6% NO, 1.2% SO2, and 4.1% H2O by mass. What is the partial pressure exerted by gas?42 Air is often dry air, ignoring the water mole fractions of in dry air 0.7808 and 0.2095, respectively. If the atmospheric pressure outside is 0.944 atm and the pressure associated with water is 0.039 atm, what are the partial of nitrogen and oxygen.43 In an experiment, a mixture of gases occupies a volume of 30.00 L at a temperature of 122.5 C. The mixture contains 14.0 g of water, 11.5 g of oxygen, and 37.3 g of nitrogen. Calculate the total pressure and the partial pressure of each gas.5.44PAE 5.45PAE 5.46PAE 47 HCl(g) reacts with ammonia gas, NH3(g), to form solid ammonium chloride. If a sample of ammonia occupying 250 mL at 21 C and a pressure of 140 torr is allowed to react with excess HCl, what mass of NH4Cl will form?48 Hydrogen gas is generated when acids come into contact with certain metals. When excess hydrochloric acid reacts with 2.5 g of Zn (the metal product is Zn2+), what volume of hydrogen gas is collected at a pressure of 0.93 atm and a temperature of 22 C?5.49PAE 50 The first step in processing zinc metal from its ore, ZnS, is to react it with O2 according to the reaction 2ZnS(s)+3O2(g)2ZnO(s)+2SO2(g) If 620 kg of ZnS is to be reacted, what volume of oxygen at 0.977 atm 34.0 C is needed (at a minimum) to carry out this reaction?51 What volume of oxygen at 24 C and 0.88 atm is needed to completely react via combustion with 45 g of methane gas?52 If tetraborane, B4H10, is treated with pure oxygen, it burns to give B2O3 and H2O: 2B4H10(s)+11O2(g)4B2O3(s)+10H2O(g) If a 0.050-g sample of tetraborane burns completely in O2, what will be the pressure of the gaseous water in a 4.25-L flask at 30.0 C?53 N2O5is an unstable gas that decomposes according to the following reaction: 2N2O5(g)4NO2(g)+O2(g) What would be the total pressure of gases present if a 10.0-L container 22.0 C begins with 0.400 atm of N2O5 and the gas completely decomposes?54 One way to generate oxygen is to heat potassium chlorate, KClO3. (The other product is potassium chloride.) If 386 mL of oxygen at 41 C and 97.8 kPa is generated by this reaction, what is the minimum mass of KClO3used?55 Ammonia is not the only possible fertilizer. Others include urea, which can be produced by the reaction: CO2(g)+2NH3(g)CO(NH2)2(s)+H2O(g) A scientist has 75 g of dry ice to provide the carbon dioxide. If 4.50 L of ammonia at 15 C and a pressure of 1.4 atm is added, which reactant is limiting? What mass of urea will form?56 Consider the following reaction: 6NiO(s)+4CIF3(g)6NiF2(s)+2Cl2(g)+3O2(g) What mass of NiO will react with a sample of ClF3 ags that has a pressure of 250 torr in a 2.5-L flask at 20 C?57 What volume of hydrogen gas, in liters, is produced by the reaction of 3.43 g of iron metal with 40.0 mL of 2.43 M HCl? The gas is collected at 2.25 atm of pressure and 23 C. The other product is FeCl2?58 Magnesium will burn in air to form both Mg3N2 and MgO. What mass of each product would be found if burning a 3.11-g sample of magnesium to completion produces a combined total of 5.09 g of the two products?59 During a collision, automobile air bags are inflated by the N2 gas formed by the explosive decomposition of sodium azide, NaN3: 2NaN32Na+3N2 What mass of sodium azide would be needed to inflate a 30.0-L bag to a pressure of 1.40 atm at 25 C?60 Automakers are always investigating reactions for the generation of gas to inflate air bags, in part the because the sodium produced in the decomposition of NaN3 (see Problem 5.59) presents safety concerns. One system that has been considering is the oxidation of graphite by Strontium nitrate, as Sr(NO3)2as shown in the equation below: 5C(s)+2Sr(NO3)2(s)2SrO(s)+2N2(g)+5CO2(g) . Suppose that a System is being designed using this reaction and the goal is to generate enough gas to inflate a bag 61 L and 1.3 atm at 23 C. What is the minimum mass of graphite that should be used in the design of this system?61 As one step in its purification, nickel metal reacts with carbon monoxide to form a compound called nickel tetracarbonyl, Ni(CO)4, which is a gas at temperature above about 316 K. A 2.000-L flask is filled with CO gas to a pressure of 748 torr at 350.0 K, and then 5.00 g of Ni is added. If the reaction describe occurs and goes to completion at constant temperature, what will the final pressure in the falsk be?62 Ammonium dinitramide (ADN), NH4N(NO2)2, was considered as a possible replacement for aluminium chloride as the oxidizer in the solid fuel booster rockets used to launch the space shuttle. When detonated by a spark, AND rapidly decomposes to produce a gaseous mixture of N2,O2, and H2O. (This is not a combustion reaction. The ADN is the only reactant.) The reaction releases a lot of heat, so the gases are initially formed at high temperature and pressure. The thrust of the rocket results mainly from the expansion of this gas mixture. Suppose a 2.3-kg sample of ADN is denoted and decomposes completely to give N2,O2, and H2O. If the resulting gas mixture expands until it reaches a temperature of 100°C and a pressure of 1.00 atm, what volume will it occupy? Is your answer consistent with the proposed use of ADN as a rocket fuel?5.63PAE 5.64PAE 5.65PAE 5.66PAE 5.67PAE 5.68PAE 5.69PAE 5.70PAE 5.71PAE 5.72PAE 5.73PAE 5.74PAE 5.75PAE 5.76PAE 5.77PAE 5.78PAE 5.79PAE 5.80PAE 5.81PAE 82 Why do heavier gases move more slowly than light gases at the same temperature?83 Suppose that speed distribution for each of the following gases were added to Figure 5.7. Which of the four gases in the original figure would each most closely resemble? Explain your answer. (a) Ar (b) Ne (c) CH4 84 Consider a sample of an ideal gas with n and T held constant. Which of the graphs below represents the proper relationship between P and V? How would the graph differ for a sample with a larger number of moles?5.85PAE 5.86PAE 5.87PAE 88 Liquid oxygen for use as a rocket fuel can be produced by cooling dry air to 183°C, where the O2 condenses. How many liters of dry air at 25°C and 750 torr would need to be processed to produce 150 L of liquid O2 at 183°C? (The mole fraction of oxygen in dry air is 0.21, and the density of liquid oxygen is 1.14g/mL.)89 A number of compounds containing the heavier noble gases, and especially xenon, have been prepared. One of these is xenon hexafluoride (XeF6), which can be prepared by heating a mixture of xenon and fluoride gases. XeF6 is a white crystalline solid at room temperature and melts at about 325 K. A mixture of 0.0600 g of Xe and 0.0304 g of F2 is sealed into a 100.0-mL bulb. (The bulb is heated, and the reaction goes to completion. Then the sealed bulb is cooled back to 20.0°C. What will be the final pressure in the bulb, expressed in torr?5.90PAE 91 A 0.2500-g sample of an Al-Zn alloy reacts with HCl to form hydrogen gas: 2Al(s)+6H+(aq)2Al3+(aq)+3H2(g) Zn(s)+2H+(aq)Zn2+(aq)+H2(g) The hydrogen produced has a volume of 0.147 L at 25°C and 755 mm Hg. What is the percentage of zinc in the alloy?5.92PAE 93 The complete combustion of octane can be used as a model for the burning of gasoline: 2C8H18+25O216CO2+18H2O Assuming that this equation provides a reasonable model of the actual combustion process, what volume of air at 1.0 atm and 25°C must be taken into an engine to burn 1 gallon of gasoline? (The partial pressure of oxygen in air is 0.21 atm and the density of liquid octane is 0.70 g/mL.)94 Mining engineers often have to deal with gases when planning for the excavation of coal. Some of these gases, including methane, can be captured and used as fuel to support the mining operation. For a particular mine, 2.4 g of CH4 is present for every 100.0 g of coal that is extracted. If 45.6% of the methane can be captured and the daily production of the mine is 580 metric tons of coal, how many moles of methane could be obtained per day?95 Some engineering designs call for the use of compressed air for underground work. If water containing iron(II) ions is present, oxygen in the compressed air may react according to the following unbalanced net ionic equation: Fe2++H++O2Fe3++H2O (a) Write the balanced net ionic equation. Remember that the amounts of each substance and the charges must balance. (b) Assume all of the oxygen from 650 L of compressed air at 15°C and 6.5 atm is lost by this reaction. What mass of water would be produced? (The mole fraction of oxygen in air is about 0.21.) (c) What will be the final pressure after the loss of the oxygen?5.96PAE 97 Homes in rural areas where natural gas service is not available often rely on propane to fuel kitchen ranges. The propane is stored as a liquid, and the gas to be burned is produced as the liquid evaporates. Suppose an architect has hired you to consult on the choice of a propane tank for such a new home. The propane gas consumed in 1.0 hour by a typical range burner at high power would occupy roughly 165 L at 25°C and 1.0 atm, and the range chosen by the client will have six burners. If the tank under consideration holds 500.0 gallons of liquid propane, what is the minimum number of hours it would take for the range to consume an entire tankful of propane? The density of liquid propane is 0.5077 kg/L.5.98PAE 99 Pure gaseous nitrogen dioxide (NO2) cannot be obtained, because NO2dimerizes, or combines with itself, to produce a mixture of NO2 and N2O4. A particular mixture of NO2, and N2O4 has a density of 2.39 g/L at 50°C and 745 torr. What is the partial pressure of NO2 in this mixture?5.100PAE 5.101PAE 102 A mixture of helium and neon gases has a density of 0.285 g/L at 31.0°C and 374 torr. Find the mole fraction of neon in this mixture.5.103PAE 104 When a 0.817-g sample of a copper oxide is heated with excess hydrogen gas, a reaction takes place, and 0.187 g of water is formed. What is the apparent formula of the copper oxide?105 The decomposition of mercury(II) thiocyanate produces an odd brown snake-like mass that is so unusual the process was once used in fireworks displays. There are actually several reactions that take place when the solid Hg(SCN)2 is ignited: 2Hg(SCN)2(s)2HgS(s)+CS2(s)+C3N4(s)CS2(s)+3O2(g)CO2(g)+2SO2(g)2C3N4(s)3(CN)2(g)+N2(g)HgS(s)+O2(g)Hg(l)+SO2(g) A 42.4-g sample of Hg(SCN)2 is placed into a 2.4-L vessel at 21°C. The vessel also contains air at a pressure of 758 torr. The container is sealed and the mixture is ignited, causing the reaction sequence above to occur. Once the reaction is complete, the container is cooled back to the original temperature of 21°C. (a) Without doing numerical calculations, predict whether the final pressure in the vessel will be greater than, less than, or equal to the initial pressure. Explain your answer. (b) Calculate the final pressure and compare your result with your prediction. (Assume that the mole fraction of O2 in air is 0.21.)5.106PAE 107 A soft drink can’s label indicates that the volume of the soda it contains is 12 oz or 355 mL. There is probably some empty space at the top of the can. Describe what you can measure and how that measurement allows you to determine the actual density of the soda.5.108PAE 109 An ore sample with a mass of 670 kg contains 27.7% magnesium carbonate, MgCO3. If all of the magnesium carbonate in this ore sample is decomposed to form carbon dioxide, describe how to determine what volume of CO2 is evolved during the process. What would have to be measured to predict the needed volume in advance?5.110PAE 111 Consider a room that is 14ft20ft wih an 8-ft ceiling. (a) How many molecules of air are present in this room at 20°C and 750 torr? (b) If a pollutant is present at 2.3 ppm, how many pollutant molecules are in this room?5.112PAE 113 A 0.0125-g sample of a gas with an empirical formula of CHF2 is placed in a 165-mL flask. It has a pressure of 13.7 mm Hg at 22.5°C. What is the molecular formula of the compound?5.114PAE describe trace analysis and explain its role in materials testing.describe waves in terms of frequency, wavelength, and amplitude.3CO relate the frequency, wavelength, and amplitude of light to characteristics such as color and brightness.describe the photoelectric effect by stating what sort of experiment is involved and what results are seen.6CO • use Planck’s equation to calculate the energy of a photon from its wavelength or frequency.8CO 9CO • describe similarities and differences between the Bohr model and the quantum mechanical model of atomic structure.11CO 12CO • identify an orbital (as 1s, 3p, etc.) from its quantum numbers, or vice versa.

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