Challenge Problems A Glencoe Program Hands-On Learning: Laboratory Manual, SE/TE Forensics Laboratory Manual, SE/TE CBL Laboratory Manual, SE/TE Small-Scale Laboratory Manual, SE/TE ChemLab and MiniLab Worksheets Review/Reinforcement: Study Guide for Content Mastery, SE/TE Solving Problems: A Chemistry Handbook Reviewing Chemistry Guided Reading Audio Program Applications and Enrichment: Challenge Problems Supplemental Problems Teacher Resources: Lesson Plans Block Scheduling Lesson Plans Spanish Resources Section Focus Transparencies and Masters Math Skills Transparencies and Masters Teaching Transparencies and Masters Solutions Manual Technology: Chemistry Interactive CD-ROM Vocabulary PuzzleMaker Software, Windows/MacIntosh Glencoe Science Web site: science.glencoe.com Assessment: Chapter Assessment MindJogger Videoquizzes (VHS/DVD) Computer Test Bank, Windows/MacIntosh Copyright © by The McGraw-Hill Companies, Inc All rights reserved Permission is granted to reproduce the material contained herein on the condition that such material be reproduced only for classroom use; be provided to students, teachers, and families without charge; and be used solely in conjunction with the Chemistry: Matter and Change program Any other reproduction, for use or sale, is prohibited without prior written permission of the publisher Send all inquiries to: Glencoe/McGraw-Hill 8787 Orion Place Columbus, OH 43240-4027 ISBN 0-07-824533-8 Printed in the United States of America 10 045 09 08 07 06 05 04 03 02 01 CHALLENGE PROBLEMS Contents Chapter Production of Chlorofluorocarbons, 1950–1992 Chapter Population Trends in the United States Chapter Physical and Chemical Changes Chapter Isotopes of an Element Chapter Quantum Numbers Chapter Döbereiner’s Triads Chapter Abundance of the Elements Chapter Comparing the Structures of Atoms and Ions Chapter Exceptions to the Octet Rule Chapter 10 Balancing Chemical Equations 10 Chapter 11 Using Mole-Based Conversions 11 Chapter 12 Mole Relationships in Chemical Reactions 12 Chapter 13 Intermolecular Forces and Boiling Points 13 Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Chapter 14 A Simple Mercury Barometer 14 Chapter 15 Vapor Pressure Lowering 15 Chapter 16 Standard Heat of Formation 16 Chapter 17 Determining Reaction Rates 17 Chapter 18 Changing Equilibrium Concentrations in a Reaction 18 Chapter 19 Swimming Pool Chemistry 19 Chapter 20 Balancing Oxidation–Reduction Equations 20 Chapter 21 Effect of Concentration on Cell Potential 21 Chapter 22 Structural Isomers of Hexane 22 Chapter 23 Boiling Points of Organic Families 23 Chapter 24 The Chemistry of Life 24 Chapter 25 The Production of Plutonium-239 25 Chapter 26 The Phosphorus Cycle 26 Answer Key T27 Challenge Problems Chemistry: Matter and Change iii iv Chemistry: Matter and Change Challenge Problems Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Name CHAPTER Date Class CHALLENGE PROBLEMS C hlorofluorocarbons (CFCs) were first produced in the laboratory in the late 1920s They did not become an important commercial product until some time later Eventually, CFCs grew in popularity until their effect on the ozone layer was discovered in the 1970s The graph shows the combined amounts of two important CFCs produced between 1950 and 1992 Answer the following questions about the graph Amount of CFCs (billion kilograms) Production of Chlorofluorocarbons, 1950–1992 400 350 300 250 200 150 100 50 1950 1960 Use with Chapter 1, Section 1.1 1970 Year 1980 1990 What was the approximate amount of CFCs produced in 1950? In 1960? In 1970? In what year was the largest amount of CFCs produced? About how much was produced that year? Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc During what two-year period did the production of CFCs decrease by the greatest amount? By about how much did their production decrease? During what two-year period did the production of CFCs increase by the greatest amount? What was the approximate percent increase during this period? How confident would you feel about predicting the production levels of CFCs during the odd numbered years 1961, 1971, and 1981? Explain Could the data in the graph be presented in the form of a circle graph? Explain Challenge Problems Chemistry: Matter and Change • Chapter 1 Name Date CHAPTER Class CHALLENGE PROBLEMS Population Trends in the United States Use with Chapter 2, Section 2.4 T he population of the United States is becoming more diverse The circle graphs below show the distribution of the U.S population among five ethnic groups in 1990 and 2000 The estimated total U.S population for those two years was 2.488 ϫ 108 in 1990 and 2.754 ϫ 108 in 2000 U.S Population Distribution African American 11.8% Hispanic American 9.0% Asian American 2.8% Native American 0.70% 1990 2000 African American 12.2% Hispanic American 11.8% Caucasian 75.7% Asian American 3.8% Native American 0.70% Caucasian 71.4% (Percentages may not add up to 100% due to rounding.) By how much did the total U.S population increase between 1990 and 2000? What was Calculate the total population for each of the five groups for 1990 and 2000 Make a bar graph that compares the population for the five groups in 1990 and 2000 In what ways is the bar graph better than the circle graphs? In what way is it less useful? Chemistry: Matter and Change • Chapter Challenge Problems Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc the percent increase during this period? Name CHAPTER Date Class CHALLENGE PROBLEMS Physical and Chemical Changes Use with Chapter 3, Section 3.2 P hysical and chemical changes occur all around us One of the many places in which physical and chemical changes occur is the kitchen For example, cooking spaghetti in a pot of water on the stove involves such changes For each of the changes described below, tell (a) whether the change that occurs is physical or chemical, and (b) how you made your choice between these two possibilities If you are unable to decide whether the change is physical or chemical, tell what additional information you would need in order to make a decision As the water in the pot is heated, its temperature rises As more heat is added, the water begins to boil and steam is produced Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc The heat used to cook is produced by burning natural gas in the stove burner The metal burner on which the pot rests while being heated becomes red as its temperature rises After the flame has been turned off, a small area on the burner has changed in color from black to gray A strand of spaghetti has fallen onto the burner, where it turns black and begins to smoke When the spaghetti is cooked in the boiling water, it becomes soft Challenge Problems Chemistry: Matter and Change • Chapter 3 Name Date CHAPTER Class CHALLENGE PROBLEMS Isotopes of an Element mass spectrometer is a device for separating atoms and molecules according to their mass A substance is first heated in a vacuum and then ionized The ions produced are accelerated through a magnetic field that separates ions of different masses The graph below was produced when a certain element (element X) was analyzed in a mass spectrometer Use the graph to answer the questions below 30 Percent abundance A Use with Chapter 4, Section 4.3 25 20 15 10 190 192 194 196 198 200 202 204 206 208 210 Atomic mass (amu) How many isotopes of element X exist? What is the mass of the most abundant isotope? What is the mass of the least abundant isotope? What is the mass of the heaviest isotope? What is the mass of the lightest isotope? Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Estimate the percent abundance of each isotope shown on the graph Without performing any calculations, predict the approximate atomic mass for element X Explain the basis for your prediction Using the data given by the graph, calculate the weighted average atomic mass of element X Identify the unknown element Chemistry: Matter and Change • Chapter Challenge Problems Name Date CHAPTER Class CHALLENGE PROBLEMS Quantum Numbers Use with Chapter 5, Section 5.2 T he state of an electron in an atom can be completely described by four quantum numbers, designated as n, ᐉ, mᐉ, and ms The first, or principal, quantum number, n, indicates the electron’s approximate distance from the nucleus The second quantum number, ᐉ, describes the shape of the electron’s orbit around the nucleus The third quantum number, mᐉ, describes the orientation of the electron’s orbit compared to the plane of the atom The fourth quantum number, ms, tells the direction of the electron’s spin (clockwise or counterclockwise) The Schrödinger wave equation imposes certain mathematical restrictions on the quantum numbers They are as follows: n can be any integer (whole number), Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc ᐉ can be any integer from to n Ϫ 1, mᐉ can be any integer from Ϫᐉ to ϩᐉ, and or Ϫ ms can be ϩ ᎏ ᎏ 2 As an example, consider electrons in the first energy level of an atom, that is, n ϭ In this case, ᐉ can have any integral value from to (n Ϫ 1), or to (1 Ϫ 1) In other words, ᐉ must be for these electrons Also, the only value that mᐉ can have is The electrons in or Ϫ for m These restrictions agree with the this energy level can have values of ϩ ᎏ ᎏ s 2 observation that the first energy level can have only two electrons Their quantum numbers and 1, 0, Ϫ are 1, 0, 0, ϩ ᎏ ᎏ 2 Use the rules given above to complete the table listing the quantum numbers for each electron in a boron atom The correct quantum numbers for one electron in the atom is provided as an example Boron (B) Electron n ᐉ mᐉ ms 1 0 ϩᎏ 2 Challenge Problems Chemistry: Matter and Change • Chapter 5 Name Date CHAPTER Class CHALLENGE PROBLEMS Döbereiner’s Triads Use with Chapter 6, Section 6.2 O ne of the first somewhat successful attempts to arrange the elements in a systematic way was made by the German chemist Johann Wolfgang Döbereiner (1780–1849) In 1816, Döbereiner noticed that the then accepted atomic mass of strontium (50) was midway between the atomic masses of calcium (27.5) and barium (72.5) Note that the accepted atomic masses for these elements today are very different from their accepted atomic masses at the time Döbereiner made his observations Döbereiner also observed that strontium, calcium, and barium showed a gradual gradation in their properties, with the values of some of strontium’s properties being about midway between the values of calcium and barium Döbereiner eventually found four other sets of three elements, which he called triads, that followed the same pattern In each triad, the atomic mass of the middle element was about midway between the atomic masses of the other two elements Unfortunately, because Döbereiner’s system did not turn out to be very useful, it was largely ignored Set Element Melting Point (°C) Ϫ219.6 Fluorine Chlorine Set Calculated: Element Actual: Boiling Point (°C) Krypton Ϫ153 Calculated: Element Tin Actual: Calcium Lead Chemistry: Matter and Change • Chapter Calculated: Strontium 1384 Set Melting Point (°C) 937 Calculated: Element Boiling Point (°C) Beryllium Magnesium Actual: Ϫ62 1107 Actual: 39.098 Germanium Boiling Point (°C) Magnesium Set Element Radon Calculated: Potassium Set Xenon 6.941 Element Actual: Ϫ7.2 Bromine Atomic Mass Lithium Sodium Set 1285 Calculated: Actual: 327 Calcium 851 Challenge Problems Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Had Döbereiner actually discovered a way of identifying trends among the elements? Listed below are six three-element groups in which the elements in each group are consecutive members of the same group in the periodic table The elements in each set show a gradation in their properties Values for the first and third element in each set are given Determine the missing value in each set by calculating the average of the two given values Then, compare the values you obtained with those given in the Handbook of Chemistry and Physics Record the actual values below your calculated values Is the value of the property of the middle element in each set midway between the values of the other two elements in the set? Name Date CHAPTER 12 Class CHALLENGE PROBLEMS Mole Relationships in Chemical Reactions Use with Chapter 12, Section 12.2 T he mole provides a convenient way of finding the amounts of the substances in a chemical reaction The diagram below shows how this concept can be applied to the reaction between carbon monoxide (CO) and oxygen (O2), shown in the following balanced equation 2CO(g) ϩ O2(g) 2CO2(g) Use the equation and the diagram to answer the following questions Moles of CO Particles of CO Grams of CO Moles of CO2 Particles of CO2 Grams of CO2 What information is needed to make the types of conversions shown by double-arrow in the diagram? Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc What conversion factors would be needed to make the conversions represented by double-arrow in the diagram for CO? By double-arrow for CO2? What information is needed to make the types of conversions represented by double-arrows and in the diagram? What conversion factors would be needed to make the conversions represented by double-arrow in the diagram for CO? Why is it not possible to convert between the mass of a substance and the number of representative particles, as represented by double-arrow of the diagram? Why is it not possible to use the mass of one substance in a chemical reaction to find the mass of a second substance in the reaction, as represented by double-arrow in the diagram? 12 Chemistry: Matter and Change • Chapter 12 Challenge Problems Name CHAPTER Date 13 Class CHALLENGE PROBLEMS Intermolecular Forces and Boiling Points he boiling points of liquids depend partly on the mass of the particles of which they are made The greater the mass of the particles, the more energy is needed to convert a liquid to a gas, and, thus, the higher the boiling point of the liquid This pattern may not hold true, however, when there are significant forces between the particles of a liquid The graph plots boiling point versus molecular mass for group 4A and group 6A hydrides A hydride is a binary compound containing hydrogen and one other element Use the graph to answer the following questions 100 Boiling point (°C) T Use with Chapter 13, Section 13.3 H2O H2Te H2Se H2S Ϫ100 0 Group 6A hydrides SiH4 CH4 SnH4 GeH4 Group 4A hydrides 50 100 Molecular mass 150 How the boiling points of the group 4A hydrides change as the molecular masses of the hydrides change? Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc What are the molecular structure and polarity of the four group 4A hydrides? Predict the strength of the forces between group 4A hydride molecules Explain how those forces affect the boiling points of group 4A hydrides How the boiling points of the group 6A hydrides change as the molecular masses of the hydrides change? What are the molecular structure and polarity of the four group 6A hydrides? Use Table 9-4 in your textbook to determine the difference in electronegativities of the bonds in the four group 6A hydrides Challenge Problems Chemistry: Matter and Change • Chapter 13 13 Name Date CHAPTER 14 Class CHALLENGE PROBLEMS A Simple Mercury Barometer I n Figure 1, a simple mercury barometer is made by filling a long glass tube with mercury and then inverting the open end of the tube into a bowl of mercury Answer the following questions about the simple mercury barometer shown here Use with Chapter 14, Section 14.1 Glass tube Mercury column What occupies the space above the mercury column in the Bowl of mercury barometer’s glass tube? At sea level At 500 meters above sea level Figure Figure 2 What prevents mercury from flowing out of the glass tube into the bowl of mercury? When the barometer in Figure is moved to a higher elevation, such as an altitude of Suppose the barometer in Figure was carried into an open mine 500 meters below sea level How would the height of the mercury column change? Explain why Suppose the liquid used to make the barometer was water instead of mercury How would this substitution affect the barometer? Explain Suppose a tiny crack formed at the top of the barometer’s glass tube How would this event affect the column of mercury? Explain why 14 Chemistry: Matter and Change • Chapter 14 Challenge Problems Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc 5000 meters, the column of mercury changes as shown in Figure Why is the mercury column lower in Figure than in Figure 1? Name CHAPTER Date 15 Class CHALLENGE PROBLEMS Vapor Pressure Lowering Use with Chapter 15, Section 15.3 Y ou have learned that adding a nonvolatile solute to a solvent lowers the vapor pressure of that solvent The amount by which the vapor pressure is lowered can be calculated by means of a relationship discovered by the French chemist François Marie Raoult (1830–1901) in 1886 According to Raoult’s law, the vapor pressure of a solvent (P) is equal to the product of its vapor pressure when pure (P0) and its mole fraction (X) in the solution, or P ϭ P0X The solution shown at the right was made by adding 75.0 g of sucrose (C12H22O11) to 500.0 g of water at a temperature of 20°C Answer the following questions about this solution Solution Water molecule Sucrose molecule Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Why the sugar molecules in the solution lower the vapor pressure of the water? What is the number of moles of sucrose in the solution? What is the number of moles of water in the solution? What is the mole fraction of water in the solution? What is the vapor pressure of the solution if the vapor pressure of pure water at 20°C is 17.54 mm Hg? How much is the vapor pressure of the solution reduced from that of water by the addition of the sucrose? Challenge Problems Chemistry: Matter and Change • Chapter 15 15 Name Date CHAPTER 16 Class CHALLENGE PROBLEMS Standard Heat of Formation C(s) ϩ O2(g) H ⌬H ϭ Ϫ110 kJ/mol CO(g) ϩ O (g) 2 ⌬H ϭ Ϫ393 kJ/mol Enthalpy ess’s law allows you to determine the standard heat of formation of a compound when you know the heats of reactions that lead to the production of that compound The first diagram on the right shows how Hess’s law can be used to calculate the heat of formation of CO2 by knowing the heats of reaction of two steps leading to the production of CO2 Use this diagram to help you answer the questions below about the second diagram Use with Chapter 16, Section 16.4 ⌬H ϭ Ϫ283 kJ/mol The equations below show how NO2 can be formed in two ways: directly from the elements or in two steps ⌬H ϭ 33 kJ/mol 1 ᎏ N2(g) ϩ ᎏ O2(g) NO(g) 2 ⌬H ϭ 91 kJ/mol O (g) NO (g) NO(g) ϩ ᎏ 2 ⌬H ϭ Ϫ58 kJ/mol CO2(g) C NO(g) ؉ 1/2 O2(g) On the diagram at the right, draw arrowheads to show the directions in which the three lines labeled 1, 2, and should point Write the correct reactants and/or products on ⌬H ؍؊58 kJ/mol each of the lines labeled A, B, and C ⌬H ؍91 kJ/mol each number on the diagram Enthalpy Write the correct enthalpy change next to B NO2(g) ⌬H ؍33 kJ/mol A 16 Chemistry: Matter and Change • Chapter 16 1/2 N2(g) ؉ O2(g) Challenge Problems Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc ᎏ N2(g) ϩ O2(g) NO2(g) or Name Date CHAPTER 17 Class CHALLENGE PROBLEMS Determining Reaction Rates initrogen pentoxide decomposes to produce nitrogen dioxide and oxygen as represented by the following equation 2N2O5(g) 4NO2(g) ϩ O2(g) The graph on the right represents the concentration of N2O5 remaining as the reaction proceeds over time Answer the following questions about the reaction 1.6 Concentration (mol/L) D Use with Chapter 17, Section 17.1 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 10 Time (h) What is the concentration of N2O5 at the beginning of the experiment? After hour? After hours? After 10 hours? By how much does the concentration of N2O5 change during the first hour of the Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc reaction? Calculate the percentage of change the concentration undergoes during the first hour of the reaction The instantaneous rate of reaction is defined as the change in concentration of reactant during some specified time period, or instantaneous rate of reaction = [N2O5]/t What is the instantaneous rate of reaction for the decomposition of N2O5 for the time period between the first and second hours of the reaction? Between the second and third hours? Between the sixth and seventh hours? What is the instantaneous rate of reaction for the decomposition of N2O5 between the sec- ond and fourth hours of the reaction? Between the third and eighth hours of the reaction? How long does it take for 0.10 mol of N2O5 to decompose during the tenth hour of the reaction? What is the average rate of reaction for the decomposition of N2O5 overall? Challenge Problems Chemistry: Matter and Change • Chapter 17 17 Name Date CHAPTER 18 Class CHALLENGE PROBLEMS R eversible reactions eventually reach an equilibrium condition in which the concentrations of all reactants and products are constant Equilibrium can be disturbed, however, by the addition or removal of either a reactant or product The graph on the right shows how the concentrations of the reactants and product of a reaction change when equilibrium is disturbed Use the graph to answer the following questions Concentration (mol/L) Changing Equilibrium Concentrations in a Reaction Use with Chapter 18, Section 18.1 SO2 SO2 O2 O2 SO3 SO3 10 Time (sec) Write the equation for the reaction depicted in the graph Write the equilibrium constant expression for the reaction Explain the shapes of the curves for the three gases during the first minutes of the At approximately what time does the reaction reach equilibrium? How you know equilibrium has been reached? What are the concentrations of the three gases at equilibrium? Calculate the value of Keq for the reaction Describe the change made in the system minutes into the reaction Tell how you know the change was made At what time does the system return to equilibrium? 18 Chemistry: Matter and Change • Chapter 18 Challenge Problems Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc reaction Name CHAPTER Date 19 Class CHALLENGE PROBLEMS Swimming Pool Chemistry Use with Chapter 19, Section 19.2 T he presence of disease-causing bacteria in swimming pools is a major health concern Chlorine gas is added to the water in some large commercial swimming pools to kill bacteria However, in most home swimming pools, either solid calcium hypochlorite (Ca(OCl)2) or an aqueous solution of sodium hypochlorite (NaOCl) is used to treat the water Both compounds dissociate in water to form the weak acid hypochlorous acid (HOCl) Hypochlorous acid is a highly effective bactericide By contrast, the hypochlorite ion (OClϪ) is not a very effective bactericide Use the information above to answer the following questions about the acid-base reactions that take place in swimming pools Write an equation that shows the reaction between hypochlorous acid and water Identify the acid, base, conjugate acid, and conjugate base in this reaction Write an equation that shows the reaction that occurs when the hypochlorite ion (OClϪ), Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc in the form of calcium hypochlorite or sodium hypochlorite, is added to water Name the acid, base, conjugate acid, and conjugate base in this reaction What effect does the addition of hypochlorite ion have on the pH of swimming pool water? The effectiveness of hypochlorite ion as a bactericide depends on pH How does high pH affect the equilibrium reaction described in question 2? What effect would high pH have on the bacteria? In the presence of sunlight, hypochlorite ion decomposes to form chloride ion and oxygen gas Write an equation for this reaction and tell how it affects the safety of pool water Challenge Problems Chemistry: Matter and Change • Chapter 19 19 Name Date CHAPTER 20 Class CHALLENGE PROBLEMS Balancing Oxidation– Reduction Equations Use with Chapter 20, Section 20.3 S cientists have developed a number of methods for protecting metals from oxidation One such method involves the use of a sacrificial metal A sacrificial metal is a metal that is more easily oxidized than the metal it is designed to protect Galvanized iron, for example, consists of a piece of iron metal covered with a thin layer of zinc When galvanized iron is exposed to oxygen, it is the zinc, rather than the iron, that is oxidized Water heaters often contain a metal rod that is made by coating a heavy steel wire with magnesium or aluminum In this case, the magnesium or aluminum is the sacrificial metal, protecting the iron casing of the heater from corrosion The diagram shows a portion of a water heater containing a sacrificial rod Answer the following questions about the diagram Steel wire Sacrificial metal Iron casing Water In the absence of a sacrificial metal, oxygen dissolved in water may react with the iron Balance the oxidation–reduction equation for this reaction: Fe(s) ϩ O2(aq) ϩ H2O Fe(OH)2(aq) Write the two half-reactions for this example of corrosion Suppose the sacrificial rod in the diagram above is coated with aluminum metal Write the balanced equation for the reaction of aluminum with oxygen dissolved in the water (Hint: The product formed is aluminum hydroxide (Al(OH)3) Write the two half-reactions for this example of corrosion Suppose that some iron in the casing of the water heater is oxidized, as shown in the equation of question above The sacrificial metal (aluminum, in this case) immediately restores the Fe2ϩ ions to iron atoms Write two half-reactions that represent this situation 20 Chemistry: Matter and Change • Chapter 20 Challenge Problems Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc casing of the heater One product formed is iron(II) hydroxide (Fe(OH)2) Which element is oxidized and which is reduced in this reaction? Name Date 21 CHAPTER Class CHALLENGE PROBLEMS Effect of Concentration on Cell Potential Use with Chapter 21, Section 21.1 I n a voltaic cell where all ions have a concentration of 1M, the cell potential is equal to the standard potential For cells in which ion concentrations are greater or less than 1M, as shown below, an adjustment must be made to calculate cell potential That adjustment is expressed by the Nernst equation: [product ion]x 0.0592 log ᎏᎏ Ecell ϭ E 0cell Ϫ ᎏ и n [reactant ion]y In this equation, n is the number of moles of electrons transferred in the reaction, and x and y are the coefficients of the product and reactant ions, respectively, in the balanced half-cell reactions for the cell Voltmeter Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Ag Ag؉ 1.0 ؋ 10؊2M Cu Cu2؉ 1.0 ؋ 10؊3M Write the two half-reactions and the overall cell reaction for the cell shown above Use Table 21-1 in your textbook to determine the standard potential of this cell Write the Nernst equation for the cell Calculate the cell potential for the ion concentrations shown in the cell Challenge Problems Chemistry: Matter and Change • Chapter 21 21 Name Date CHAPTER 22 Class CHALLENGE PROBLEMS Structural Isomers of Hexane Use with Chapter 22, Sections 22.1 and 22.3 T he structural formula of an organic compound can sometimes be written in a variety of ways, but sometimes structural formulas that appear similar can represent different compounds The structural formulas below are ten ways of representing compounds having the molecular formula C6H14 a CH3 CH2 e CH3 CH2 CH2 CH2 CH3 CH2 CH3 CH i CH2 CH2 CH3 CH3 CH2 CH2 CH3 CH3 CH3 CH2 CH CH2 CH3 b CH3 CH f CH3 CH2 CH2 CH3 CH CH CH3 CH3 CH3 j CH2 CH3 c g CH2 CH3 CH3 CH CH CH3 CH3 CH CH2 CH3 CH3 CH3 h CH3 CH3 C CH2 CH3 CH3 CH3 CH3 CH CH2 CH2 CH3 In the spaces provided, write the correct name for each of the structural formulas, labeled a–j, above a e i b f j c g d h How many different compounds are represented by the structural formulas above? What are their names? 22 Chemistry: Matter and Change • Chapter 22 Challenge Problems Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc d Name CHAPTER Date 23 Class CHALLENGE PROBLEMS Boiling Points of Organic Families he most important factor determining the boiling point of a substance is its atomic or molecular mass In general, the larger the atomic or molecular mass of the substance, the more energy is needed to convert the substance from the liquid phase to the gaseous phase As an example, the boiling point of ethane (molecular mass ϭ 30; boiling point ϭ Ϫ89°C) is much higher than the boiling point of methane (molecular mass ϭ 16; boiling point ϭ Ϫ161°C) Intermolecular forces between the particles of a liquid also can affect the liquid’s boiling point The graph shows trends in the boiling points of four organic families: alkanes, alcohols, aldehydes, and ethers Use the graph and your knowledge of intermolecular forces to answer the following questions 100 Boiling point (°C) T Use with Chapter 23, Section 23.3 50 Ϫ50 30 40 50 60 70 Molecular mass ϭ alkane ϭ alcohol 80 ϭ aldehyde ϭ ether Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc For any one family, what is the relationship between molecular mass and boiling point? For compounds of similar molecular mass, which family of the four shown in the graph has the lowest boiling points? Which family has the highest boiling points? Find and list the boiling points for ethanol (molecular mass ϭ 46) and dimethyl ether (molecular mass ϭ 46) on the graph Why would you expect these two compounds to have relatively similar boiling points? Find the aldehyde with a molecular mass of about 58 Name that aldehyde and write its chemical formula Can this aldehyde form hydrogen bonds? Can other aldehydes form hydrogen bonds? Explain Challenge Problems Chemistry: Matter and Change • Chapter 23 23 Name Date 24 CHALLENGE PROBLEMS The Chemistry of Life Use with Chapter 24, Section 24.4 P roteins are synthesized when RNA molecules translate the DNA language of nitrogen bases into the protein language of amino acids using a genetic code The genetic code is found in RNA molecules called messenger RNA (mRNA), which are synthesized from DNA molecules The genetic code consists of a sequence of three nitrogen bases in the mRNA, called a codon Most codons code for specific amino acids A few codons code for a stop in the synthesis of proteins The table shows the mRNA codons that make up the genetic code To use the table, read the three nitrogen bases in sequence The first base is shown along the left side of the table The second base is shown along the top of the table The third base is shown along the right side of the table For example, the sequence CAU codes for the amino acid histidine (His) The table gives abbreviations for the amino acids Answer the following questions about the genetic code The Genetic Code Second base U C A G } } C UCU Phe UCC UCA Leu UCG CCU CCC Leu CCA CCG ACU Ile ACC ACA Met ACG GCU GCC Val GCA GCG A UAU UAC Ser UAA UAG CAU CAC Pro CAA CAG AAU AAC Thr AAA AAG GAU GAC Ala GAA GAG G }Tyr Stop Stop } His } Gln } Asn } Lys } Asp } Glu UGU UGC UGA UGG CGU CGC CGA CGG AGU AGC AGA AGG GGU GGC GGA GGG } Cys } } U C Stop A Trp G U C Arg A G U Ser C A Arg G U C Gly A G Third base First base U UUU UUC UUA UUG CUU CUC CUA CUG AUU AUC AUA AUG GUU GUC GUA GUG What amino acid is represented by each of the following codons? a CUG b UCA Write the sequence of amino acids for which the following mRNA sequence codes -C-A-U-C-A-C-C-G-G-U-C-U-U-U-U-C-U-U- Errors sometimes occur when mRNA molecules are synthesized from DNA molecules Nitrogen bases may be omitted, an extra nitrogen base may be added, or a nitrogen base may be changed during synthesis The two mRNA sequences shown below are examples of such errors In each case, tell how the mRNA sequence shown differs from the correct mRNA sequence given in question a -C-A-U-C-A-C-C-G-G-U-U-C-U-U-U-U-C-U-U- b -C-A-U-U-A-C-C-G-G-U-C-U-U-U-U-C-U-U- Write the amino acid sequence for each of the mRNA sequences shown in question a b 24 Chemistry: Matter and Change • Chapter 24 Challenge Problems Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc CHAPTER Class Name CHAPTER Date 25 Class CHALLENGE PROBLEMS The Production of Plutonium-239 Use with Chapter 25, Section 25.4 45p 75n W hen nuclear fission was first discovered, only two isotopes, uranium-233 and uranium-235, were known of being capable of undergoing this nuclear change Scientists later discovered a third isotope, plutonium-239, also could undergo nuclear fission Plutonium-239 does not occur in nature but can be made synthetically in nuclear reactors and particle accelerators 92p 143n 1n 92p 143n 1n 1n A 92p 146n Source of neutrons The diagram shows the process by which plutonium-239 is made in nuclear reactors Answer the questions about the diagram C 0␥ 1n 0 –1 –1 Identify the isotope whose nucleus is labeled A in the diagram B D F 48p 77n E G Name the type of nuclear reaction that occurs when a neutron strikes nucleus A Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Identify the isotope whose nucleus is labeled B Besides fragmented nuclei, what else is produced when a neutron strikes nucleus A? Identify the isotope whose nucleus is labeled C Write the nuclear equation for the reaction that occurs when a neutron strikes nucleus C Identify the product D formed in the reaction Write the nuclear equation for the decay of nucleus D Identify isotope E formed in the reaction Write a balanced nuclear equation for the decay of nucleus E Identify isotope F formed in the reaction Name the type of nuclear reaction that occurs when a neutron strikes nucleus F 10 Write the nuclear equation for the reaction that occurs when a neutron strikes nucleus F Identify isotope G formed in the reaction Challenge Problems Chemistry: Matter and Change • Chapter 25 25 Name Date CHAPTER 26 Class CHALLENGE PROBLEMS The Phosphorus Cycle Use with Chapter 26, Section 26.4 P hosphorus is an important element both in organisms and in the lithosphere In organisms, phosphorus occurs in DNA and RNA molecules, cell membranes, bones and teeth, and in the energy–storage compound adenosine triphosphate (ATP) In the lithosphere, phosphorus occurs primarily in the form of phosphates, as a major constituent of many rocks and minerals Phosphate rock is mined to produce many commercial products, such as fertilizers and detergents When these products are used, phosphates are returned to the lithosphere and hydrosphere Thus, phosphorus—like carbon and nitrogen—cycles in the environment Use the diagram of the phosphorus cycle to answer the questions below Phosphate rocks Phosphate rocks Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc Geological uplift By what methods does phosphorus get into soil? By what method plants obtain the phosphorus they need? By what method animals obtain the phosphorus they need? In what way is the phosphorus cycle different from the carbon and nitrogen cycles you studied in the textbook? The phosphorus cycle has both short-term and long-term parts Use different colored pencils to show each part on the diagram 26 Chemistry: Matter and Change • Chapter 26 Challenge Problems ... T27 Challenge Problems Chemistry: Matter and Change iii iv Chemistry: Matter and Change Challenge Problems Copyright © Glencoe/ McGraw-Hill, a division of the... Content Mastery, SE/TE Solving Problems: A Chemistry Handbook Reviewing Chemistry Guided Reading Audio Program Applications and Enrichment: Challenge Problems Supplemental Problems Teacher Resources:... 18 Chemistry: Matter and Change • Chapter 18 Challenge Problems Copyright © Glencoe/ McGraw-Hill, a division of the McGraw-Hill Companies, Inc reaction Name CHAPTER Date 19 Class CHALLENGE PROBLEMS