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All Textbook Solutions for Chemistry: An Atoms First Approach

20Q When magnesium metal is added to a beaker of HCl(aq), a gas is produced. Knowing that magnesium is oxidized and that hydrogen is reduced, write the balanced equation for the reaction. How many electrons are transferred in the balanced equation? What quantity of useful work can be obtained when Mg is added directly to the beaker of HCl? How can you harness this reaction to do useful work?How can one construct a galvanic cell from two substances, each having a negative standard reduction potential?The free energy change for a reaction, G, is an extensive property. What is an extensive property? Surprisingly, one can calculate G from the cell potential. , for the reaction. This is surprising because : is an intensive property. How can the extensive property G be calculated from the intensive property ?What is wrong with the following statement: The best concentration cell will consist of the substance having the most positive standard reduction potential. What drives a concentration cell to produce a large voltage?When jump-starting a car with a dead battery, the ground jumper should be attached to a remote part of the engine block. Why?26Q 27Q Consider the following electrochemical cell: a. If silver metal is a product of the reaction, is the cell a galvanic cell or electrolytic cell? Label the cathode and anode, and describe the direction of the electron flow. b. If copper metal is a product of the reaction, is the cell a galvanic cell or electrolytic cell? Label the cathode and anode, and describe the direction of the electron flow. c. If the above cell is a galvanic cell, determine the standard cell potential. d. If the above cell is an electrolytic cell, determine the minimum external potential that must be applied to cause the reaction to occur.Balance the following oxidationreduction reactions that occur in acidic solution using the halfreaction method. a. I(aq)+ClO(aq)I3(aq)+Cl(aq) b. As2O3(s)+NO3(aq)H3AsO4(aq)+NO(g) c. Br(aq)+MnO4(aq)Br2(l)+Mn2+(aq) d. CH3OH(aq)+Cr2O72(aq)CH2O(aq)+Cr3+(aq)30E 31E 32E Chlorine gas was first prepared in 1774 by C. W. Scheele by oxidizing sodium chloride with manganese(IV) oxide. The reaction is NaCl(aq)+H2SO4(aq)+MnO2(s)Na2SO4(aq)+MnCl2(aq)+H2O(l)+Cl2(g) Balance this equation.Gold metal will not dissolve in either concentrated nitric acid or concentrated hydrochloric acid It will dissolve, however, in aqua regia, a mixture of the two concentrated acids. The products of the reaction are the AuCl4 ion and gaseous NO. Write a balanced equation for the dissolution of gold in aqua regia.35E Consider the following galvanic cell: a. Label the reducing agent and the oxidizing agent, and describe the direction of the electron flow. b. Determine the standard cell potential. c. Which electrode increases in mass as the reaction proceeds, and which electrode decreases in mass?37E Sketch the galvanic cells based on the following overall reactions. Show the direction of electron flow, the direction of ion migration through the salt bridge, and identify the cathode and anode. Give the overall balanced equation. Assume that all concentrations are 1.0 M and that all partial pressures are 1.0 atm. a. IO3(aq)+Fe2+(aq)Fe3+(aq)+I2(aq) b. Zn(s)+Ag+(aq)Zn2+(aq)+Ag(s)39E 40E 41E 42E 43E Give the standard line notation for each cell in Exercises 38 and 42.45E 46E 47E 48E 49E The amount of manganese in steel is determined by changing it to permanganate ion. The steel is first dissolved in nitric acid, producing Mn2+ ions. These ions are then oxidized to the deeply colored MnO4 ions by periodate ion (IO4) in acid solution. a. Complete and balance an equation describing each of the above reactions. b. Calculate and G at 25C for each reaction.51E 52E Estimate for the half-reaction 2H2O+2eH2+2OH given the following values of Gfo: H2O(l)=237kJ/mol H2(g)=0.0 OH(aq)=157kJ/mol e=0.0 Compare this value of with the value of given in Table 17-1.54E Glucose is the major fuel for most living cells. The oxidative breakdown of glucose by our body to produce energy is called respiration. The reaction for the complete combustion of glucose is C6H12O6(s)+6O2(g)6CO2(g)+6H2O(l) If this combustion reaction could be harnessed as a fuel cell, calculate the theoretical voltage that could be produced at standard conditions. (Hint: Use Gf values from Appendix 4.)Direct methanol fuel cells (DMFCs) have shown some promise as a viable option for providing green energy to small electrical devices. Calculate for the reaction that takes place in DMFCs: CH3OH(l)+3/2O2(g)CO2(g)+2H2O(l) Use values of Gffrom Appendix 4.57E Using data from Table 17-1, place the following in order of increasing strength as reducing agents (all under standard conditions). Cu+,F,H,H2O,I2,K Answer the following questions using data from Table 17-1 (all under standard conditions). a. Is H+(aq) capable of oxidizing Cu(s) to Cu2+(aq)? b. Is Fe3+ (aq) capable of oxidizing I (aq)? c. Is H2(g) capable of reducing Ag+(aq)?60E Consider only the species (at standard conditions) Na+, Cl, Ag+, Ag, Zn2+, Zn, Pb in answering the following questions. Give reasons for your answers. (Use data from Table 17-1.) a. Which is the strongest oxidizing agent? b. Which is the strongest reducing agent? c. Which species can be oxidized by SO42 (aq) in acid? d. Which species can be reduced by Al(s)?62E 63E 64E 65E 66E A galvanic cell is based on the following half-reactions at 25C: Ag++eAg H2O2+2H++2e2H2O Predict whether is larger or smaller than for the following cases. a. [Ag+]=1.0M,[H2O2]=2.0M,[H+]=2.0M b. [Ag+]=2.0M,[H2O2]=1.0M,[H+]=1.0107M 68E Consider the concentration cell shown below. Calculate the cell potential at 25C when the concentration of Ag+ in the compartment on the right is the following. a. 1.0 M b. 2.0 M c. 0.10 M d. 4.0 105 M e. Calculate the potential when both solutions are 0.10 M in Ag+. For each case, also identify the cathode, the anode, and the direction in which electrons flow.70E The overall reaction in the lead storage battery is Pb(s)+PbO2(s)+2H+(aq)+2HSO4(aq)2PbSO4(s)+2H2O(l) Calculate at 25C for this battery when [H2SO4] = 4.5 M, that is, [H+] = [HSO4] = 4.5 M. At 25C, =2.04 V for the lead storage battery.72E Consider the cell described below: Zn|Zn2+(1.00M)||Cu2+(l.00M)|Cu Calculate the cell potential after the reaction has operated long enough for the [Zn2+] to have changed by 0.20 mol/L. (Assume T=25C.)Consider the cell described below: Al|Al3+(1.00M)||Pb2+(1.00M)|Pb Calculate the cell potential after the reaction has operated long enough for the [Al3+] to have changed by 0.60 mol/L. (Assume T = 25C.)75E 76E 77E 78E 79E An electrochemical cell consists of a nickel metal electrode immersed in a solution with [Ni2+] = 1.0 M separated by a porous disk from an aluminum metal electrode. a. What is the potential of this cell at 25C if the aluminum electrode is placed in a solution in which [Al3+] = 7.2 103 M? b. When the aluminum electrode is placed in a certain solution in which [Al3+] is unknown, the measured cell potential at 25C is 1.62 V. Calculate [Al3+] in the unknown solution. (Assume Al is oxidized.)An electrochemical cell consists of a standard hydrogen electrode and a copper metal electrode. If the copper electrode is placed in a solution of 0.10 M NaOH that is saturated with Cu(OH)2, what is the cell potential at 25C? [For Cu(OH)2, Ksp = 1.6 1019.]82E Consider a concentration cell that has both electrodes made of some metal M. Solution A in one compartment of the cell contains 1.0 M M2+. Solution B in the other cell compartment has a volume of 1.00 L. At the beginning of the experiment 0.0100 mole of M(NO3)2 and 0.0100 mole of Na2SO4 are dissolved in solution B (ignore volume changes), where the reaction M2+(aq)+SO42(aq)MSO4(s) occurs. For this reaction equilibrium is rapidly established, whereupon the cell potential is found to be 0.44 V at 25C. Assume that the process M2++2eM has a standard reduction potential of 0.31 V and that no other redox process occurs in the cell. Calculate the value of Ksp for MSO4(s) at 25C.84E 85E 86E Consider the following galvanic cell at 25C: Pt|Cr2+(0.30M),Cr3+(2.0M)||Co2+(0.20M)|Co The overall reaction and equilibrium constant value are 2Cr2+(aq)+Co2+(aq)2Cr3+(aq)+Co(s)K=2.79107 Calculate the cell potential, for this galvanic cell and G for the cell reaction at these conditions.88E 89E 90E 91E The solubility product for CuI(s) is 1.1 102 Calculate the value of for the half-reaction CuI(s)+eCu(s)+I(aq)How long will it take to plate out each of the following with a current of 100.0 A? a. 1.0 kg AI from aqueous Al3+ b. 1.0 g Ni from aqueous Ni2+ c. 5.0 moles of Ag from aqueous Ag+The electrolysis of BiO+ produces pure bismuth. How long would it take to produce 10.0 g Bi by the electrolysis of a BiO+ solution using a current of 25.0 A?What mass of each of the following substances can be produced in 1.0 h with a current of 15 A? a. Co from aqueous Co2+ b. Hf from aqueous Hf4+ c. I2 from aqueous KI d. Cr from molten CrO3 96E An unknown metal M is electrolyzed. It took 74.1 s for a current of 2.00 A to plate out 0.107 g of the metal from a solution containing M(NO3)3. Identify the metal.Electrolysis of an alkaline earth metal chloride using a current of 5.00 A for 748 s deposits 0.471 g of metal at the cathode. What is the identity of the alkaline earth metal chloride?What volume of F2 gas, at 25C and 1.00 atm, is produced when molten KF is electrolyzed by a current of 10.0 A for 2.00 h? What mass of potassium metal is produced? At which electrode does each reaction occur?What volumes of H2(g) and O2(g) at STP are produced from the electrolysis of water by a current of 2.50 A in 15.0 min?101E A factory wants to produce 1.00 103 kg barium from the electrolysis of molten barium chloride. What current must be applied for 4.00 h to accomplish this?It took 2.30 min using a current of 2.00 A to plate out all the silver from 0.250 L of a solution containing Ag+ What was the original concentration of Ag+ in the solution?A solution containing Pt4+ is electrolyzed with a current of 4.00 A. How long will it take to plate out 99% of the platinum in 0.50 L of a 0.0 10-M solution of Pt4+?A solution at 25C contains 1.0 M Cd2+, 1.0 M Ag+, 1.0 M Au3+, and 1.0 M NiH2+ in the cathode compartment of an electrolytic cell. Predict the order in which the metals will plate out as the voltage is gradually increased.Consider the following half-reactions: A hydrochloric acid solution contains platinum, palladium, and iridium as chloro-complex ions. The solution is a constant. 1.0 M in chloride ion and 0.020 M in each complex ion. Is it feasible to separate the three metals from this solution by electrolysis? (Assume that 99% of a metal must be plated out before another metal begins to plate out.)In the electrolysis of an aqueous solution of Na2SO4, what reactions occur at the anode and the cathode (assuming standard conditions)?Copper can be plated onto a spoon by placing the spoon in an acidic solution of CuSO4(aq) and connecting it m a copper strip via a power source as illustrated below: a. Label the anode and cathode. and describe the direction of the electron now. b. Write out the chemical equations for the reactions that occur at each electrode.109E 110E 111E What reaction will take place at the Cathode and the anode when each of the following is electrolyzed? (Assume Standard conditions.) a. 1.0 M KF solution b. 1.0 M CuCl2 solution c. 1.0 M MgI2 solution Gold is produced electrochemically from an aqueous solution of Au(CN)2 containing an excess of CN. Gold metal and oxygen gas are produced at the electrodes. What amount (moles) of O2 will be produced during the production of 1.00 mole of gold?114AE The saturated calomel electrode. abbreviated SCE. is often used as a reference electrode in making electrochemica1 measurements. The SCE is composed of mercury in contact with a saturated solution of calomel (Hg2Cl2). The electrolyte solution is saturated KCI. is +0.242 V relative to the standard hydrogen electrode. Calculate the potential for each of the following galvanic cells containing a saturated calomel electrode and the given half-cell components at standard conditions. In each case. indicate whether the SCE is the cathode or the anode. Standard reduction potentials are found in Table 17.1. a. Cu2++2eCu b. Fe3++e-Fe2+ c. AgCl+e-Ag+Cl- d. Al3++3eAl e. Ni2++2eNi Consider the following half-reactions: Explain why platinum metal will dissolve in aqua regia (a mixture of hydrochloric and nitric acids) but not in either concentrated nitric or concentrated hydrochloric acid individually.Consider the standard galvanic cell based on the following half-reactions: Cu2++2eCuAg++eAg The electrodes in this cell are Ag(s) and Cu(s). Does the cell potential increase. decrease. or remain the same when the following changes occur to the standard cell? a. CuSO4(s) is added to the copper half-cell compartment (assume no volume change). b. NH3(aq) is added to the copper half-cell compartment (Hint: Cu2+ reacts with NH3, to form Cu(NH3)42+(aq).] c. NaCl(s) is added to the silver half .cell compartment (Hint: Ag+ reacts with Cl to form AgCl(s).] d. Water is added to both half-cell compartments until the volume or solution is doubled. e. The silver electrode is replaced with a platinum electrode 118AE The black silver sulfide discoloration of silverware can be removed by heating the silver article in a sodium carbonate solution in an aluminum pan. The reaction is 3Ag2S(s)+2Al(s)6Ag(s)+3S2(aq)+2Al3+(aq) a. Using data in Appendix 4, calculate G, K, and for the above reaction at 25C. [For Al3+(aq), Gf = 480. kJ/mol.] b. Calculate the value of the standard reduction potential for the following half-reaction: 2e+Ag2S(s)2Ag(s)+S2(aq)120AE When aluminum foil is placed in hydrochloric acid, nothing happens for the first 30 seconds or so. This is followed by vigorous bubbling and the eventual disappearance of the foil. Explain these observations.122AE 123AE The overall reaction and equilibrium constant value for a hydrogen-oxygen fuel cell at 298 K is 2H2(g)+O2(g)2H2O(l)K=1.281083 a. Calculate and G at 298 K for the fuel cell reaction. b. Predict the signs of H and S for the fuel cell reaction. c. As temperature increases, does the maximum amount of work obtained from the fuel cell reaction increase, decrease, or remain the same? Explain.What is the maximum work that can be obtained from a hydrogen-oxygen fuel cell at standard conditions that produces 1.00 kg water at 25C? Why do we say that this is the maximum work that can be obtained? What are the advantages and disadvantages in using fuel cells rather than the corresponding combustion reactions to produce electricity?The overall reaction and standard cell potential at 25C for the rechargeable nickel-cadmium alkaline battery is For every mole of Cd consumed in the cell, what is the maximum useful work that can be obtained at standard conditions?127AE 128AE 129AE 130AE 131AE 132AE 133AE 134CWP Consider a galvanic cell based on the following half-reactions: a. What is the expected cell potential with all components in their standard states? b. What is the oxidizing agent in the overall cell reaction? c. What substances make up the anode compartment? d. In the standard cell, in which direction do the electrons flow? e. How many electrons are transferred per unit of cell reaction? f. If this cell is set up at 25C with [Fe2+] = 2.00 104 M and [La3+] = 3.00 103 M, what is the expected cell potential?Consider a galvanic cell based on the following theoretical half-reactions: What is the value of G and K for this cell?Consider a galvanic cell based on the following half-reactions: a. What is the standard potential for this cell? b. A nonstandard cell is set up at 25C with [Mg2+] = 1.00 105 M. The cell potential is observed to be 4.01 V. Calculate [Au3+] in this cell.An electrochemical cell consists of a silver metal electrode immersed in a solution with [Ag+] = 1.00 M separated by a porous disk from a compartment with a copper metal electrode immersed in a solution of 10.00 M NH3 that also contains 2.4 103 M Cu(NH3)42+. The equilibrium between Cu2+ and NH3 is: Cu2+(aq)+4NH3(aq)Cu(NH3)42+(aq)K=1.01013 and the two cell half-reactions are: Assuming Ag+ is reduced, what is the cell potential at 25C?An aqueous solution of PdCl2 is electrolyzed for 48.6 seconds, and during this time 0.1064 g of Pd is deposited on the cathode. What is the average current used in the electrolysis?140CP 141CP The overall reaction in the lead storage battery is Pb(s)+PbO2(s)+2H+(aq)+2HSO4(aq)2PbSO4(s)+2H2O(l) a. For the cell reaction H = 315.9 kJ and S = 263.5 J/K. Calculate at 20.C. Assume H and S do not depend on temperature. b. Calculate at 20.C when [HSO4] = [H+] = 4.5 M. c. Consider your answer to Exercise 71. Why does it seem that batteries fail more often on cold days than on warm days?Consider the following galvanic cell: Calculate the KSP value for Ag2SO4(s). Note that to obtain silver ions in the right compartment (the cathode compartment), excess solid Ag2SO4 was added and some of the salt dissolved.144CP A galvanic cell is based on the following half-reactions: where the iron compartment contains an iron electrode and [Fe2+] = 1.00 10-3 M and the hydrogen compartment contains a platinum electrode, PH2=1.00atm, and a weak acid, HA, at an initial concentration of 1.00 M. If the observed cell potential is 0.333 V at 25C, calculate the Ka value for the weak acid HA.146CP The measurement of pH using a glass electrode obeys the Nernst equation. The typical response of a pH meter at 25 00C is given by the equation where contains the potential of the reference electrode and all other potentials that arise in the cell that are not related to the hydrogen ion concentration. Assume that = 0.250 V and that a. What is the uncertainty in the values of pH and [H+] if the uncertainty in the measured potential is 1 m V ( 0.001 V)? b. To what precision must the potential be measured for the uncertainty in pH to be 0.02 pH unit?148CP A galvanic cell is based on the following half-reactions: In this cell, the silver compartment contains a silver electrode and excess AgCl(s) (Ksp = 1.6 1010), and the copper compartment contains a copper electrode and [Cu2+] = 2.0 M. a. Calculate the potential for this cell at 25C. b. Assuming 1.0 L of 2.0 M Cu2+ in the copper compartment, calculate the moles of NH3 that would have to be added to give a cell potential of 0.52 Vat 25C (assume no volume change on addition of NH3). Cu2+(aq)+4NH3(aq)Cu(NH3)42+(aq)K=1.01013 150CP 151CP 152CP Consider the following galvanic cell: A 15 0-mole sample of NH is added to the Ag compartment (assume 1.00 L of total solution after the addition). The silver ion reacts with ammonia to form complex ions as shown: Ag+(aq)+NH3(aq)AgNH3+(aq)K1=2.1103AgNH3+(aq)+NH3(aq)Ag(NH3)2+(aq)K2=8.2103 Calculate the cell potential after the addition of 15.0 moles of NH3.When copper reacts with nitric acid, a mixture of NO(g) and NO2(g) is evolved. The volume ratio of the two product gases depends on the concentration of the nitric acid according to the equilibrium 2H+(aq)+2NO3(aq)+NO(g)3NO2(g)+H2O(l) Consider the following standard reduction potentials at 25C: a. Calculate the equilibrium constant for the above reaction. b. What concentration of nitric acid will produce a NO and NO2 mixture with only 0.20% NO2 (by moles) at 25C and 1.00 atm? Assume that no other gases are present and that the change in acid concentration can be neglected.The following standard reduction potentials have been determined for the aqueous chemistry of indium: a. What is the equilibrium constant for the disproportionation reaction, where a species is both oxidized and reduced, shown below? 3In+(aq)2In(s)+In3+(aq) b. What is Gf for In+(aq) if Gf = 97.9 kJ/mol for In3+(aq)?An electrochemical cell is set up using the following unbalanced reaction: Ma+(aq)+N(s)N2+(aq)+M(s) The standard reduction potentials are: The cell contains 0.10 M N2+ and produces a voltage of 0.180 V. If the concentration of Ma+ is such that the value of the reaction quotient Q is 9.32 103, calculate [Ma+]. Calculate wmax for this electrochemical cell.Three electrochemical cells were connected in series so that the same quantity of electrical current passes through all three cells. In the first cell, 1.15 g chromium metal was deposited from a chromium(III) nitrate solution. In the second cell, 3.15 g osmium was deposited from a solution made of Osn+ and nitrate ions. What is the name of the salt? In the third cell, the electrical charge passed through a solution containing X2+ ions caused deposition of 2.1 1 g metallic X. What is the electron configuration of X?A silver concentration cell is set up at 25C as shown below: The AgCl(s) is in excess in the left compartment. a. Label the anode and cathode, and describe the direction of the electron flow. b. Determine the value of Ksp for AgCl at 25C.A galvanic cell is based on the following half-reactions: In this cell, the copper compartment contains a copper electrode and [Cu2+] = 1.00 M, and the vanadium compartment contains a vanadium electrode and V2+ at an unknown concentration. The compartment containing the vanadium (1.00 L of solution) was titrated with 0.0800 M H2EDTA2, resulting in the reaction H2EDTA2(aq)+V2+(aq)VEDTA2(aq)+2H+(aq)K=? The potential of the cell was monitored to determine the stoichiometric point for the process, which occurred at a volume of 500.0 mL H2EDTA2 solution added. At the stoichiometric point, was observed to be 1 .98 V. The solution was buffered at a pH of 10.00. a. Calculate before the titration was carried out. b. Calculate the value of the equilibrium constant, K, for the titration reaction. c. Calculate at the halfway point in the titration.160MP 1RQ 2RQ 3RQ 4RQ 5RQ 6RQ 7RQ 8RQ 9RQ 10RQ 1Q 2Q 3Q 4Q 5Q 6Q 7Q 8Q 9Q 10Q 11E 12E 13E 14E 15E 16E 17E 18E 19E 20E 21E 22E 23E 24E 25E 26E 27E 28E 29E 30E 31E 32E 33E 34E 35E 36E 37E 38E 39E 40E 41E 42E 43E 44E 45E 46E 47E 48E 49E 50E 51E 52E 53E A chemist studied the reaction mechanism for the reaction 2NO(g)+O2(g)2NO2(g) by reacting N16O with 18O2. If the reaction mechanism is NO+O2NO3(fastequilibrium)NO3+NO2NO2(slow) what distribution of 18O would you expect in the NO2? Assume that N is the central atom in NO3, assume only N16O18O2 forms, and assume stoichiometric amounts of reactants are combined.55E 56E 57E 58E 59AE 60AE 61AE 62AE 63AE 64AE 65AE 66AE 67AE 68AE 69AE 70AE 71AE 72AE 73CWP 74CWP 75CWP 76CWP 77CWP 78CWP 79CP 80CP 81CP 82CP 83CP 84CP 85CP 86CP 87IP 88IP What are the two most abundant elements by mass in the earths crust, oceans, and atmosphere? Does this make sense? Why? What are the four most abundant elements by mass in the human body? Does this make sense? Why?2RQ 3RQ 4RQ 5RQ 6RQ 7RQ 8RQ 9RQ 10RQ 1Q 2Q 3Q Diagonal relationships in the periodic table exist as well as the vertical relationships. For example, Be and Al are similar in some of their properties as are B and Si. Rationalize why these diagonal relationships hold for properties such as size, ionization energy, and electron affinity.5Q 6Q 7Q 8Q 9Q 10Q 11E 12E 13E 14E 15E 16E 17E 18E 19E 20E 21E 22E 23E 24E Consider element 113. What is the expected electron configuration for element 113? What oxidation states would be exhibited by element 113 in its compounds?26E 27E 28E 29E 30E 31E 32E 33E 34E The following illustration shows the orbitals used to form the bonds in carbon dioxide. Each color represents a different orbital. Label each orbital, draw the Lewis structure for carbon dioxide, and explain how the localized electron model describes the bonding in CO2.36E Silicon is produced for the chemical and electronics industries by the following reactions. Give the balanced equation for each reaction. a. SiO2(s)+C(s)Si(s)+CO(g) b. Silicon tetrachloride is reacted with very pure magnesium, producing silicon and magnesium chloride. c. Na2SiF6(s)+Na(s)Si(s)+NaF(s)38E 39E 40E 41E 42E 43E 44E 45E 46E 47E 48E 49E 50E 51E

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