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All Textbook Solutions for Chemistry & Chemical Reactivity

1. Will SrSO4 precipitate from a solution containing 2.5 × 10−4M strontium ion, Sr2+, if enough of the soluble salt Na2SO4 is added to make the solution 2.5 × 10−4 M in SO42−? Ksp for SrSO4 is 3.4 ×10−7. yes no can’t decide Silver nitrate (0.0050 mol) is added to 1.00 L of 1 00 M NH3. What is the concentration of Ag+ ions at equilibrium? Ag+(aq)+2NH3(aq)[Ag(NH3)2]+(aq)Kf=1.1107 1. Iron(II) chloride (0.025 mol) is added to 1.00 L of 0.500 M NaCN. What is the concentration of Fe2+ ions at equilibrium? Kr for [Fe(CN)6]4− is 1.0 × 1035. 1.0 × 1035M 1.0 × 10−36 M 5.2 × 10−38M Calculate the value of the equilibrium constant, Knet, for dissolving Cu(OH)2 in aqueous ammonia (to form the complex ion [Cu(NH3)4]2+) (Figure 16.9).1. What is the equilibrium constant for the process of dissolving Agl by the addition of aqueous NaCN? Ksp for Agl is 8.5 × 10−17, and Kr for [Ag(CN)2]− is 1.3 × 1021. 6.5 × 10−4 8.7 × 104 1.1 × 105 1Q What is the minimum volume of 0.0071 M NaCN(aq) necessary to dissolve the gold from 1.0 metric ton (1000 kg) of ore if the ore contains 0.012% gold?Use the formation constant of [Au(CN)2] in Appendix K to determine the equilibrium concentration of Au+(aq) in a solution that is 0.0071 M CN and 1.1 104 M [Au(CN)2]. Is it reasonable to conclude that 100% of the gold in solution is present as the [Au(CN)2] complex ion? Explain.Silver undergoes similar reactions as those shown for gold. Both metals react with cyanide ion in the presence of oxygen to form soluble complexes, and both are reduced by zinc. The reaction of Ag+ with cyanide ion may be viewed as two sequential steps: (1) Ag+(aq)+CN(aq)AgCN(s) (2) AgCN(s)+CN(aq)[Ag(CN)2](aq)Ag+(aq)+2CN(aq)[Ag(CN)2](aq)Kf=1.31021 a. Use the solubility product equilibrium constant (Appendix J) of AgCN(s) to determine the equilibrium constant for Step 1. b. Use the equilibrium constants from Step 1 and the overall reaction to determine the equilibrium constant for Step 2. c. Excess AgCN(s) is combined with 1.0 L of 0.0071 M CN (aq) and allowed to equilibrate. Calculate the equilibrium concentrations of CN and [Ag(CN)2] using the equilibrium constant for Step 2. Assume no change in volume occurs.Write a balanced chemical equation for the reaction of NaAu(CN)2(aq) and Zn(s).Phosphate ions are abundant in cells, both as the ions themselves and as important substituents on organic molecules. Most importantly, the pKa for the H2PO4 ion is 7.20, which is very close to the normal pH in the body. H2PO4(aq) + H2O() H3O+(aq) + HPO42(aq) 1. What should the ratio [HPO42]/[H2PO4] be to control the pH at 7.40?A typical total phosphate concentration in a cell, [HPO42] + [H2PO4], is 2.0 102 M. What are the concentrations of HPO42 and HPO4 at pH 7.40?Does the pH of the solution increase, decrease or stay the same when you (a) add solid ammonium chloride to a dilute aqueous solution of NH3? (b) add solid sodium acetate to a dilute aqueous solution of acetic acid? (c) add solid NaCl to a dilute aqueous solution of NaOH?Does the pH of the solution increase, decrease, or stay the same when you (a) add solid sodium oxalate, Na2C2O4, to 50.0 mL of 0.015 M oxalic acid, H2C2O4? (b) add solid ammonium chloride to 75 mL of 0.016 M HCl? (c) add 20.0 g of NaCl to 1.0 L of 0.10 M sodium acetate, NaCH3CO2?What is the pH of a solution that consists of 0.20 M ammonia, NH3, and 0.20 M ammonium chloride, NH4Cl?What is the pH of 0.15 M acetic acid to which 1.56 g of sodium acetate, NaCH3CO2 has been added?What is the pH of the solution that results from adding 30.0 mL of 0.015 M KOH to 50.0 mL of 0.015 M benzoic acid?What is the pH of the solution that results from adding 25.0 mL of 0.12 M HCl to 25.0 mL of 0.43 M NH3?What is the pH of the buffer solution that contains 2.2 g of NH4Cl in 250 mL of 0.12 M NH3? Is the final pH lower or higher than the pH of the 0.12 M ammonia solution?Lactic acid (CH3CHOHCO2H) is found in sour milk, in sauerkraut, and in muscles after activity. (Ka for lactic acid = 1.4 104.) (a) If 2.75 g of NaCH3CHOHCO2, sodium lactate, is added to 5.00 102 mL of 0.100 M lactic acid, what is the pH of the resulting buffer solution? (b) Is the pH of the buffered solution lower or higher than the pH of the lactic acid solution?What mass of sodium acetate, NaCH3CO2, must he added to 1.00 L of 0.10 M acetic acid to give a solution with a pH of 4.50?What mass of ammonium chloride, NH4Cl, must be added to exactly 5.00 102 mL of 0.10 M NH3 solution to give a solution with a pH of 9.00?Calculate the pH of a solution that has an acetic acid concentration of 0.050 M and a sodium acetate concentration of 0.075 M.Calculate the pH of a solution that has an ammonium chloride concentration of 0.050 M and an ammonia concentration of 0.045 M.What must the ratio of acetic acid to acetate ion be to have a buffer with a pH value of 5.00?What must the ratio of H2PO4 to HPO42 be to have a buffer with a pH value of 7.00?A buffer is composed of formic acid and its conjugate base, the formate ion. (a) What is the pH of a solution that has a formic acid concentration of 0.050 M and a sodium formate concentration of 0.035 M? (b) What must the ratio of acid to conjugate base be to have a pH value 0.50 units higher than the value calculated in part (a)?A buffer solution is composed of 1.360 g of KH2PO4 and 5.677 g of Na2HPO4. (a) What is the pH of the buffer solution? (b) What mass of KH2PO4 must be added to decrease the buffer solution pH by 0.50 unit from the value calculated in part (a)?Which of the following combinations would be the best to buffer the pH of a solution at approximately 9? (a) HCl and NaCl (b) NH3 and NH4C1 (c) CH3CO2H and NaCH3CO2 Which of the following combinations would be the best to buffer the pH of a solution at approximately 7? (a) H3PO4 and NaH2PO4 (b) NaH2PO4 and Na2HPO4 (c) Na2HPO4 and Na3PO4 Describe how to prepare a buffer solution from NaH2PO4 and Na2HPO4 to have a pH of 7.5.Describe how to prepare a buffer solution from NH3 and NH4Cl to have a pH of 9.5.Determine the volume (in mL) of 1.00 M NaOH that must be added to 250 mL of 0.50 M CH3CO2H to produce a buffer with a pH of 4.50.Determine the volume (in mL) of 1.00 M HC1 that must be added to 750 mL of 0.50 M HPO42 to produce a buffer with a pH of 7.00.A buffer solution was prepared by adding 4.95 g of sodium acetate, NaCH3CO2, to 2.50 102 mL of 0.150 M acetic acid, CH3CO2H. (a) What is the pH of the buffer? (b) What is the pH of 1.00 102 mL of the buffer solution if you add 82 mg of NaOH to the solution?You dissolve 0.425 g of NaOH in 2.00 L of a buffer solution that has [H2PO4| = [HPO42] = 0.132 M. What is the pH of the solution before adding NaOH? After adding NaOH?A buffer solution is prepared by adding 0.125 mol of ammonium chloride to 5.00 102 mL of 0.500 M solution of ammonia. (a) What is the pH of the buffer? (b) If 0.0100 mol of HCl gas is bubbled into 5.00 102 mL of the buffer, what is the new pH of the solution?What is the pH change when 20.0 mL of 0.100 M NaOH is added to 80.0 mL of a buffer solution consisting of 0.169 M NH3 and 0.183 M NH4Cl?Phenol, C6H5OH, is a weak organic acid. Suppose 0.515 g of the compound is dissolved in enough water to make 125 mL of solution. The resulting solution is titrated with 0.123 M NaOH. C6H5OH(aq) + OH(aq) C6H5O(aq) + H2O() (a) What is the pH of the original solution of phenol? (b) What are the concentrations of all of the following ions at the equivalence point: Na+, H3O+, OH, and C6H5O? (c) What is the pH of the solution at the equivalence point?Assume you dissolve 0.235 g of the weak acid benzoic acid, C6H5CO2H, in enough water to make 1.00 102 mL of solution and then titrate the solution with 0.108 M NaOH. C6H5CO2H(aq) + OH(aq) C6H5CO2(aq) + H2O() (a) What was the pH of the original benzoic add solution? (b) What are the concentrations of all of the following ions at the equivalence point: Na+, H3O+, OH, and C6H5CO2? (c) What is the pH of the solution at the equivalence point?You require 36.78 mL of 0.0105 M HCl to reach the equivalence point in the titration of 25.0 mL of aqueous ammonia. (a) What was the concentration of NH3 in the original ammonia solution? (b) What are the concentrations of H3O+, OH, and NH4+ at the equivalence point? (c) What is the pH of the solution at the equivalence point?A titration of 25.0 mL of a solution of the weak base aniline, C6H5NH2, requires 25.67 mL of 0.175 M HCl to reach the equivalence point. C6H5NH2(aq) + H3O+(aq) C6H5NH3+(aq) + H2O() (a) What was the concentration of aniline in the original solution? (b) What are the concentrations of H3O+, OH, and C6H5NH3+ at the equivalence point? (c) What is the pH of the solution at the equivalence point?Without doing detailed calculations, sketch the curve for the titration of 30.0 mL of 0.10 M NaOH with 0.10 M HCl. Indicate the approximate pH at the beginning of the titration and at the equivalence point. What is the total solution volume at the equivalence point?Without doing detailed calculations, sketch the curve for the titration of 50 mL of 0.050 M pyridine, C6H5N (a weak base), with 0.10 M HCl. Indicate the approximate pH at the beginning of the titration and at the equivalence point. What is the total solution volume at the equivalence point?You titrate 25.0 mL of 0.10 M NH3 with 0.10 M HCl. (a) What is the pH of the NH3 solution before the titration begins? (b) What is the pH at the equivalence point? (c) What is the pH at the halfway point of the titration? (d) What indicator in Figure 17.11 could be used to detect the equivalence point? (e) Calculate the pH of the solution after adding 5.00, 15.0, 20.0, 22.0, and 30.0 mL of the acid. Combine this information with that in parts (a)(c) and plot the titration curve.Using Figure 17.11, suggest an indicator to use in each of the following titrations: (a) The weak base pyridine is titrated with HCl. (b) Formic acid is titrated with NaOH. (c) Ethylenediamine, a weak diprotic base, is titrated with HCl. Figure 17.11 Common acid-base indicators. The color changes occur over a range of pH values. Notice that o few indicators hove color changes over two different pH ranges.Using Figure 17.11, suggest an indicator to use in each of the following titrations. (a) NaHCO3 is titrated to CO32 with NaOH. (b) Hypochlorous acid is titrated with NaOH. (c) Trimethylamine is titrated with HCl.Name two insoluble salts of each of the following ions. (a) Cl (b) Zn2+ (c) Fe2+38PS Using the solubility guidelines (Figure 3.10), predict whether each of the following is insoluble or soluble in water. (a) (NH4)2CO3 (b) ZnSO4 (c) NiS (d) BaSO4 Predict whether each of the fallowing is insoluble or soluble in water. (a) Pb(NO3)2 (b) Fe(OH)3 (c) ZnCl2 (d) CuS For each of the following insoluble salts, (1) write a balanced equation showing the equilibrium occurring when the salt is added to water, and (2) write the Ksp expression. (a) AgCN (b) NiCO3 (c) AuBr3 42PS When 1.55 g of solid thallium(I) bromide is added to 1.00 L of water, the salt dissolves to a small extent. TlBr(s)Tl+(aq)+Br(aq) The thallium(I) and bromide ions in equilibrium with TlBr each have a concentration of 1.9 103 M. What is the value of Ksp for TlBr?At 20 C, a saturated aqueous solution of silver acetate, AgCH3CO2, contains 1.0 g of the silver compound dissolved in 100.0 mL of solution. Calculate Ksp for silver acetate. AgCH3CO2(s)Ag+(aq)+CH3CO2(aq)When 250 mg of SrF2, strontium fluoride, is added to 1.00 L of water, the salt dissolves to a very small extent. SrF2(s)Sr2+(aq)+2F(aq) At equilibrium, the concentration of Sr2+ is found to be 1.03 103 M. What is the value of Ksp for SrF2?Calcium hydroxide, Ca(OH)2, dissolves in water to the extent of 1.78 g per liter. What is the value of Ksp for Ca(OH)2? Ca(OH)2(s)Ca2+(aq)+2OH(aq)You add 0.979 g of Pb(OH)2 to 1.00 L of pure water at 25 C. The pH is 9.15. Estimate the value of Ksp for Pb(OH)2.You place 1.234 g of solid Ca(OH)2 in 1.00 L of pure water at 25 C. The pH of the solution is found to be 12.68. Estimate the value of Ksp for Ca(OH)2.Estimate the solubility of silver iodide in pure water at 25 C (a) in moles per liter and (b) in grams per liter. AgI(s)Ag+(aq)+I(aq)What is the molar concentration of Au+(aq) in a saturated solution of AuCl in pure water at 25 C? AgCl(s)Au+(aq)+Cl(aq)51PS Estimate the solubility of lead(II) bromide (a) in moles per liter and (b) in grams per liter of pure water.The Ksp value for radium sulfate, RaSO4, is 4.2 1011. If 25 mg of radium sulfate is placed in 1.00 102 mL of water, does all of it dissolve? If not, how much dissolves?If 55 mg of lead(II) sulfate is placed in 250 mL of pure water, does all of it dissolve? If not, how much dissolves?55PS 56PS Calculate the molar solubility of silver thiocyanate, AgSCN, in pure water and in water containing 0.010 M NaSCN.Calculate the solubility of silver bromide, AgBr, in moles per liter, in pure water. Compare this value with the molar solubility of AgBr in 225 mL of water to which 0.15 g of NaBr has been added.Compare the solubility, in milligrams per milliliter, of silver iodide, AgI, (a) in pure water and (b) in water that is 0.020 M in AgNO3.What is the solubility, in milligrams per milliliter, of BaF2, (a) in pure water and (b) in water containing 5.0 mg/mL KF?Calculate the solubility, in moles per liter, of iron(II) hydroxide, Fe(OH)2, in a solution buffered to a pH of 7.00.Calculate the solubility, in moles per liter, of calcium hydroxide, Ca(OH)2, in a solution buffered to a pH of 12.60.Which insoluble compound in each pair should be more soluble in nitric acid than in pure water? (a) PbCl2 or PbS (b) Ag2CO3 or AgI (c) Al(OH)3 or AgCl Which compound in each pair is more soluble in water than is predicted by a calculation from Ksp? (a) AgI or Ag2CO3 (b) PbCO3 or PbCl2 (c) AgCl or AgCN You have a solution that has a lead(II) ion concentration of 0.0012 M. If enough soluble chloride-containing salt is added so that the Cl concentration is 0.010 M, will PbCl2 precipitate?Sodium carbonate is added to a solution in which the concentration of Ni2+ ion is 0.0024 M. Will precipitation of NiCO3 occur (a) when the concentration of the carbonate ion is 1.0 106 M or (b) when it is 100 times greater (1.0 104 M)?If the concentration of Zn2+ in 10.0 mL of water is 1.63 104 M, will zinc hydroxide, Zn(OH)2, precipitate when 4.0 mg of NaOH is added?You have 95 mL of a solution that has a lead(II) concentration of 0.0012 M. Will PbCl2 precipitate when 1.20 g of solid NaCl is added?69PS Will a precipitate of Mg(OH)2 form when 25.0 mL of 0.010 M NaOH is combined with 75.0 mL of a 0.10 M solution of magnesium chloride?Zinc hydroxide is amphoteric (Section 16.10). Use equilibrium constants to show that, given sufficient OH, Zn(OH)2 can dissolve in NaOH.Solid silver iodide, AgI, can be dissolved by adding aqueous sodium cyanide. Calculate Knet the following reaction. AgI(s)+2CN[Ag(CN)2](aq)+I(aq)What amount of ammonia (moles) must be added to dissolve 0.050 mol of AgCl suspended in 1.0 L of water?Can you dissolve 15.0 mg of AuCl in 100.0 mL of water if you add 15.0 mL of 6.00 M NaCN?What is the solubility of AgCl (a) in pure water and (b) in 1.0 M NH3?76PS 77GQ 78GQ 79GQ Calculate the hydronium ion concentration and the pH of the solution that results when 20.0 mL of 0.15 M acetic acid, CH3CO2H, is mixed with 5.0 mL of 0.17 M NaOH.Calculate the hydronium ion concentration and the pH of the solution that results when 50.0 mL of 0.40 M NH3 is mixed with 25.0 mL of 0.20 M HCl.For each of the following cases, decide whether the pH is less than 7, equal to 7, or greater than 7. (a) Equal volumes of 0.10 M acetic acid, CH3CO2H, and 0.10 M KOH are mixed. (b) 25 mL of 0.015 M NH3 is mixed with 12 mL of 0.015 M HCl. (c) 150 mL of 0.20 M HNO3, is mixed with 75 mL of 0.40 M NaOH. (d) 25 mL of 0.45 M H2SO4 is mixed with 25 mL of 0.90 M NaOH.83GQ A sample of hard water contains about 2.0 103 M Ca2+. A soluble fluoride-containing salt such as NaF is added to fluoridate the water (to aid in the prevention of dental cavities). What is the maximum concentration of F that can be present without precipitating CaF2?What is the pH of a buffer solution prepared from 5.15 g of NH4NO3 and 0.10 L of 0.15 M NH3? What is the new pH if the solution is diluted with pure water to a volume of 5.00 102 mL?86GQ Describe the effect on the pH of the following actions or explain why there is not an effect: (a) Adding sodium acetate, NaCH3CO2, to 0.100 M CH3CO2H (b) Adding NaNO3 to 0.100 M HNO3 What volume of 0.120 M NaOH must be added to 100. mL of 0.100 M NaHC2O4 to reach a pH of 4.70?A buffer solution is prepared by dissolving 1.50 g each of benzoic acid, C6H5CO2H, and sodium benzoate, NaC6H5CO2, in 150.0 mL of solution. (a) What is the pH of this buffer solution? (b) Which buffer component must be added, and in what quantity, to change the pH to 4.00? (c) What quantity of 2.0 M NaOH or 2.0 M HCl must be added to the buffer to change the pH to 4.00?What volume of 0.200 M HCl must be added to 500.0 mL of 0.250 M NH3 to have a buffer with a pH of 9.00?What is the equilibrium constant for the following reaction? AgCl(s)+I(aq)AgI(s)+Cl(aq) Does the equilibrium lie predominantly to the left or to the right? Will AgI form if iodide ion. I, is added to a saturated solution of AgCl?Calculate the equilibrium constant for the following reaction. Zn(OH)2(s)+2CN(aq)Zn(CN)2(s)+2OH(aq) Does the equilibrium lie predominantly to the left or to the right?93GQ The solubility product constant for calcium oxalate is estimated to be 4 109. What is its solubility in grams per liter?In principle, the ions Ba2+ and Ca2+ can be separated by the difference in solubility of their fluorides, BaF2 and CaF2. If you have a solution that is 0.10 M in both Ba2+ and Ca2+, CaF2, will begin to precipitate first as fluoride ion is added slowly to the solution. (a) What concentration of fluoride ion will precipitate the maximum amount of Ca2+ ion without precipitating BaF2? (b) What concentration of Ca2+ remains in solution when BaF2 just begins to precipitate?A solution contains 0.10 M iodide ion, I, and 0.10 M carbonate ion, CO32. (a) If solid Pb(NO3)2 is slowly added to the solution, which salt will precipitate first, Pbl2 or PbCO3? (b) What will be the concentration of the first ion that precipitates (CO32 or I) when the second, more soluble salt begins to precipitate?A solution contains Ca2+ and Pb2+ ions, both at a concentration of 0.010 M. You wish to separate the two ions from each other as completely as possible by precipitating one but not the other using aqueous Na2SO4 as the precipitating agent. (a) Which will precipitate first as sodium sulfate is added, CaSO4 or PbSO4? (b) What will be the concentration of the first ion that precipitates (Ca2+ or Pb2+) when the second, more soluble salt begins to precipitate?98GQ 99GQ 100GQ Each pair of ions below is found together in aqueous solution. Using the table of solubility product constants in Appendix J, devise a way to separate these ions by adding a reagent to precipitate one of the ions as an insoluble salt and leaving the other in solution. (a) Ba2+ and Na+ (b) Ni2+ and Pb2+Each pair of ions below is found together in aqueous solution. Using the table of solubility product constants in Appendix J, devise a way to separate these ions by adding a reagent to precipitate one of the ions as an insoluble salt and leave the other in solution. (a) Cu2+ and Ag+ (b) A13+ and Fe3+The cations Ba2+ and Sr2+ can be precipitated as very insoluble sulfates. (a) If you add sodium sulfate to a solution containing these metal cations, each with a concentration of 0.10 M, which is precipitated first, BaSO4 or SrSO4? (b) What will be the concentration of the first ion that precipitates (Ba2+ or Sr2+) when the second, more soluble salt begins to precipitate?You will often work with salts of Fe3+, Pb2+, and Al3+ in the laboratory. (All are found in nature, and all are important economically.) If you have a solution containing these three ions, each at a concentration of 0.10 M, what is the order in which their hydroxides precipitate as aqueous NaOH is slowly added to the solution?Aniline hydrochloride, (C6H5NH3)Cl, is a weak acid. (Its conjugate base is the weak base aniline, C6H5NH2.) The acid can be titrated with a strong base such as NaOH. C6H5NH3+(aq)+OH(aq)C6H5NH2(aq)+H2O(l) Assume 50.0 mL of 0.100 M aniline hydrochloride is titrated with 0.185 M NaOH. (Ka for aniline hydrochloride is 2.4 105.) (a) What is the pH of the (C6H5NH3) solution before the titration begins? (b) What is the pH at the equivalence point? (c) What is the pH at the halfway point of the titration? (d) Which indicator in Figure 17.11 could be used to detect the equivalence point? (e) Calculate the pH of the solution after adding 10.0, 20.0, and 30.0 mL of base. (f) Combine the information in parts (a), (b), (c), and (e), and plot an approximate titration curve.The weak base ethanolamine. HOCH2CH2NH2, can be titrated with HCl. HOCH2CH2NH2(aq)+H3O+(aq)HOCH2CH2NH3+(aq)+H2O(l) Assume you have 25.0 mL of a 0.010 M solution of ethanolamine and titrate it with 0.0095 M HCl. (Kb for ethanolamine is 3.2 107.) (a) What is the pH of the ethanolamine solution before the titration begins? (b) What is the pH at the equivalence point? (c) What is the pH at the halfway point of the titration? (d) Which indicator in Figure 17.11 would be the best choice to detect the equivalence point? (e) Calculate the pH of the solution after adding 5.00, 10.0, 20.0, and 30.0 mL of the acid. (f) Combine the information in parts (a), (b), (c), and (e), and plot an approximate titration curve.For the titration of 50.0 mL of 0.150 M ethylamine. C2H5NH2, with 0.100 M HCl, find the pH at each of the following points, and then use that information to sketch the titration curve and decide on an appropriate indicator. (a) At the beginning, before HCl is added (b) At the halfway point in the titration (c) When 75% of the required acid has been added (d) At the equivalence point (e) When 10.0 mL more HCl has been added than is required (f) Sketch the titration curve. (g) Suggest an appropriate indicator for this titration.A buffer solution with it pH of 12.00 consists of Na3PO4 and Na2HPO4. The volume of solution is 200.0 mL. (a) Which component of the buffer is present in a larger amount? (b) If the concentration of Na3PO4 is 0.400 M, what mass of Na2HPO4 is present? (c) Which component of the buffer must be added to change the pH to 12.25? What mass of that component is required?To have a buffer with a pH of 2.50, what volume of 0.150 M NaOH must be added to 100. mL of 0.230 M H3PO4?What mass of Na3PO4 must be added to 80.0 mL of 0.200 M HCl to obtain a buffer with a pH of 7.75?You have a solution that contains AgNO3, Pb(NO3)2, and Cu(NO3)2. Devise a separation method that results in having Ag+ in one test tube, Pb2+ in another, and Cu2+ in a third test tube. Use solubility guidelines and Ksp and Kf values.112IL Suggest a method for separating a precipitate consisting of a mixture of solid CuS and solid Cu(OH)2.114SCQ 115SCQ Two acids, each approximately 0.01 M in concentration, are titrated separately with a strong base. The adds show the following pH values at the equivalence point: HA, pH = 9.5, and HB, pH = 8.5. (a) Which is the stronger acid, HA or HB? (b) Which of the conjugate bases, A or B, is the stronger base?Composition diagrams, commonly known as alpha plots, are often used to visualize the species in a solution of an acid or base as the pH is varied. The diagram for 0.100 M acetic acid is shown here. The plot shows how the fraction [alpha ()] of acetic acid in solution, =[CH3CO2H][CH3CO2H]+[CH3CO2] changes as the pH increases (blue curve). (The red curve shows how the fraction of acetate ion, CH3CO2, changes as the pH increases.) Alpha plots are another way of viewing the relative concentrations of acetic acid and acetate ion as a strong base is added to a solution of acetic acid in the course of a titration. (a) Explain why the fraction of acetic acid declines and that of acetate ion increases as the pH increases. (b) Which species predominates at a pH of 4, acetic acid or acetate ion? What is the situation at a pH of 6? (c) Consider the point where the two lines cross. The fraction of acetic acid in the solution is 0.5, and so is that of acetate ion. That is, the solution is half acid and half conjugate base; their concentrations are equal. At this point, the graph shows the pH is 4.74. Explain why the pH at this point is 4 74.The composition diagram, or alpha plot, for the important acid-base system of carbonic acid, H2CO3, is illustrated. (See Study Question 1.7 for more information on such diagrams.) (a) Explain why the fraction of bicarbonate ion, HCO3, rises and then falls as the pH increases. (b) What is the composition of the solution when the pH is 6.0? When the pH is 10.0? (c) If you wanted to buffer a solution at a pH of 11.0, what should be the ratio of HCO3 to CO32?The chemical name for aspirin is acetylsalicylic acid. It is believed that the analgesic and other desirable properties of aspirin are due not to the aspirin itself but rather to the simpler compound salicylic add, C6H4(OH)CO2H, which results from the breakdown of asp inn in the stomach. Salicylic acid (a) Give approximate values for the following bond angles in the acid: (i) CCC in the ring, (ii) OC=O; (iii) either of the COH angles: and (iv) CCH. (b) What is the hybridization of the C atoms of the ring? Of the C atom in the CO2H group? (c) Experiment shows that 1.00 g of the acid will dissolve in 460 ml of water. If the pH of this solution is 2.4, what is Ka for the acid? (d) If you have salicylic acid in your stomach and if the pH of gastric juice is 2.0, calculate the percentage of salicylic add that will be present in the stomach in the form of the salicylate ion, C6H4(OH)CO2. (e) Assume you have 25.0 mL of a 0.014 M solution of salicylic acid and titrate it with 0.010 M NaOH. What is the pH at the halfway point of the titration? What is the pH at the equivalence point?120SCQ 1. A process is spontaneous in the direction that moves it away from equilibrium toward equilibrium A process that is reactant-favored at equilibrium can never be spontaneous. This statement is (a) true (b) false 3RC In a spontaneous process, S(universe) is (a) 0 (b) = 0 (c) 0 2. Which of the following is true for a spontaneous process but not for a nonspontaneous process? Energy in the universe is concentrated conserved dispersed not conserved 3RC 1RC 2RC Predict which substance in each pair has the higher entropy and explain your reasoning. (a) O2(g) or O3(g) (b) SnCl4() or SnCl4(g)2CYU Without looking up their standard entropies in reference tables, identify which of the following lists the materials in order of increasing entropy. (a) H2O() NaCl(s) NH3(g) (b) H2O() NH3(g) NaCl(s) (c) NaCl(s) H2O() NH3(g) (d) NH3(g) H2O() NaCl(s)Without doing any calculations, predict the sign of rS for the following reaction: Zn(s) + 2 HCl(aq) ZnCl2(aq) + H2(g) (a) rS 0 (b) rS = 0 (c) rS 0 Calculate rS for the following reaction at 25 C. 2 H2(g) + O2(g) 2 H2O() (a) 326.6 J/K mol-rxn (b) 139.9 J/K mol-rxn (c) 139.9 J/K mol-rxn (d) 326.6 J/K mol-rxn Based on rH and rS, predict the spontaneity of the reaction of hydrogen and chlorine to give hydrogen chloride gas under standard conditions (at 298 K). Calculate S (universe) to verify your prediction. H2(g)+Cl2(g)2HCl(g)1RC 2RC 3RC 1RC 2RC 1CYU 2CYU Oxygen was first prepared by Joseph Priestley (1733-1804) by heating HgO. Use data in Appendix L to estimate the temperature required to decompose HgO(s) into Hg() and O2(g).4CYU 5CYU 6CYU 1RC 2RC 3RC Consider the hydrolysis reactions of creatine phosphate and adenosine-5-monophosphate. Creatine Phosphate + H2O Creatine + HPi rG = 43.3 KJ/mol-rxn Adenosine-5-Honophosphate + H2O Adenosine + HPi rG = 9.2 KJ/mol-rxn Which of the following combinations produces a reaction that is product-favored at equilibrium: for creatine phosphate to transfer phosphate to adenosine or for adenosine-5-monophosphate to transfer phosphate to creatine?2Q The decomposition of diamond to graphite [C(diamond) C(graphite)] is thermodynamically favored, but occurs slowly at room temperature. a. Use fG values from Appendix L to calculate rG and Keq for the reaction under standard conditions and 298.15 K. b. Use fH and S values from Appendix L to estimate rG and Keq for the reaction at 1000 K. Assume that enthalpy and entropy values are valid at these temperatures. Does heating shift the equilibrium toward the formation of diamond or graphite? c. Why is the formation of diamond favored at high pressures? d. The phase diagram shows that diamond is thermodynamically favored over graphite at 20,000 atmospheres pressure (about 2 GPa) at room temperature. Why is this conversion actually done at much higher temperatures and pressures?It has been demonstrated that buckminsterfullerene (C60), another allotrope of carbon (Section 2.3), may be converted into diamond at room temperature and 20,000 atmospheres pressure (about 2 GPa). The standard enthalpy of formation, fH, for buckminsterfullerene is 2320 kJ/mol at 298.2 K. a. Calculate rH for the conversion of C60 to diamond at standard state conditions and 2982 K. b. Assuming that the standard entropy per mole of carbon in both C60 and diamond is comparable (both about 23 J/K mol), is the conversion of C60 to diamond product-favoredat room temperature?Which substance has the higher entropy? (a) dry ice (solid CO2) at 78 C or CO2(g) at 0 C (b) liquid water at 25 C or liquid water at 50 C (c) pure alumina, Al2O3(s), or ruby (ruby is Al2O3 in which some Al3+ ions in the crystalline lattice are replaced with Cr3+ ions) (d) one mole of N2(g) at 1 bar pressure or one mole of N2(g) at 10 bar pressure (both at 298 K)Which substance has the higher entropy? (a) a sample of pure silicon (to be used in a computer chip) or a piece of silicon containing a trace of another element such as boron or phosphorus (b) O2(g) at 0 C or O2(g) at 50 C (c) I2(s) or I2(g), both at room temperature (d) one mole of O2(g) at 1 bar pressure or one mole of O2(g) at 0.01 bar pressure (both at 298 K)Use S values to calculate the standard entropy change, rS0, for each of the following processes and comment on the sign of the change. (a) KOH(s) KOH(aq) (b) Na(g) Na(s) (c) Br2() Br2(g) (d) HCl(g) HCl(aq)Use S values to calculate the standard entropy change, rS, for each of the following processes, and comment on the sign of the change. (a) NH4C1(s) NH4Cl(aq) (b) CH3OH() CH3OH(g) (c) CCl4(g) CCl4() (d) NaCl(s) NaCl(g)Calculate the standard entropy change for the formation of 1.0 mol of the following compounds from the elements at 25 C. (a) HCl(g) (b) Ca(OH)2(s)Calculate the standard entropy change for the formation of 1.0 mol of the following compounds from the elements at 25 C. (a) H2S(g) (b) MgCO3(s)Calculate the standard entropy change for the following reactions at 25 C. Comment on the sign of rS. (a) 2 Al(s) + 3 Cl2(g) 2 AlCl3(s) (b) 2 CH3OH() + 3 O2(g) 2 CO2(g) + 4 H2O(g)Calculate the standard entropy change for the following reactions at 25 C. Comment on the sign of rS. (a) 2 Na(s) + 2 H2O() 2 NaOH(aq) + H2(g) (b) Na2CO3(s) + 2 HCl(aq) 2 NaCl(aq) + H2O() + CO2(g)Is the reaction Si(s) + 2 Cl2(g) SiCl4(g) spontaneous under standard conditions at 298.15 K? Answer this question by calculating S(system), S(surroundings), and S(universe). (Define reactants and products as the system.)Is the reaction Si(s) + 2 H2(g) SiH4(g) spontaneous under standard conditions at 298.15 K? Answer this question by calculating S(system), S(surroundings), and S(universe). (Define reactants and products as the system.)Calculate S(universe) for the decomposition of 1 mol of liquid water to form gaseous hydrogen and oxygen. Is this reaction spontaneous under standard conditions at 25 C? Explain your answer briefly.Calculate S(universe) for the formation of 1 mol HCl(g) from gaseous hydrogen and chlorine. Is this reaction spontaneous under standard conditions at 25 C? Explain your answer briefly.Classify each of the reactions according to one of the four reaction types summarized in Table 18.1. (a) Fe2O3(s) + 2 Al(s) 2 Fe(s) + Al2O3(s) rH = 851.5 kj/mol-rxn rS = 375.2 J/K mol-rxn (b) N2(g) + 2 O2(g) 2 NO2(g) rH = 66.2 kJ/mol-rxn rS = 121.6 J/K mol-rxn TABLE 18.1 Predicting Whether a Reaction Will Be Spontaneous Under Standard Conditions Classify each of the reactions according to one of the four reaction types summarized in Table 18.1. (a) C6H12O6(s) + 6 O2(g) 6 CO2(g) + 6 H2O() rH = 673 kj/mol-rxn rS = 60.4 j/K mol-rxn (b) MgO(s) + C(graphite) Mg(s) + CO(g) rH = 490.7 kJ/mol-rxn rS = 197.9 J/K mol-rxn TABLE 18.1 Predicting Whether a Reaction Will Be Spontaneous Under Standard Conditions Using values of fH and S, calculate rG for each of the following reactions at 25 C. (a) 2 Pb(s) + O2(g) 2 PbO(s) (b) NH3(g) + HNO3(aq) NH4NO3(aq) Which of these reactions is (are) predicted to be product-favored at equilibrium? Are the reactions enthalpy- or entropy-driven?Using values of fH and S, calculate rG for each of the following reactions at 25 C. (a) 2 Na(s) + 2 H2O() 2 NaOH(aq) + H2(g) (b) 6 C(graphite) + 3 H2(g) C6H6() Which of these reactions is (are) predicted to be product-favored at equilibrium? Are the reactions enthalpy- or entropy-driven?Using values of fH and S, calculate the standard molar free energy of formation, fG, for each of the following compounds: (a) CS2(g) (b) NaOH(s) (c) ICl(g) Compare your calculated values of fG with those listed in Appendix L Which of these formation reactions are predicted to be product-favored at equilibrium at 25 C?Using values of fH and S, calculate the standard molar free energy of formation, fG, for each of the following: (a) Ca(OH)2(s) (b) Cl(g) (c) Na2CO3(s) Compare your calculated values of fG with those listed in Appendix L. Which of these formation reactions are predicted to be product-favored at equilibrium at 25 C?Using values of fG, calculate rG for each of the following reactions at 25 C. Which are product-favored at equilibrium? (a) 2 K(s) + Cl2(g) 2 KCI(s) (b) 2 CuO(s) 2 Cu(s) + O2(g) (c) 4 NH3(g) + 7 O2(g) 4 NO2(g) + 6 H2O(g)Using values of fG, calculate rG for each of the following reactions at 25 C. Which are product- favored at equilibrium? (a) HgS(s) + O2(g) Hg() + SO2(g) (b) 2 H2(g) + 3 O2(g) 2 H2O(g) + 2 SO2(g) (c) SiCl4(g) + 2 Mg(s) 2 MgCl2(s) + Si(s)For the reaction BaCO3(s) BaO(s) + CO2(g), rG = +219.7 kJ/mol-rxn. Using this value and other data available in Appendix L, calculate the value of fG for BaCO3(s).For the reaction TiCl2(s) + Cl2(g) TiCl4(), rG = 272.8 kj/mol-txn. Using this value and other data available in Appendix L, calculate the value of fG for TiCl2(s).Determine whether the reactions listed below are entropy-favored or disfavored under standard conditions. Predict how an increase in temperature will affect the value of rG. (a) N2(g) + 2 O2(g) 2 NO2(g) (b) 2 C(s) + O2(g) 2 CO(g) (c) CaO(s) + CO2(g) CaCO3(s) (d) 2 NaCl(s) 2 Na(s) + Cl2(g)Determine whether the reactions listed below are entropy-favored or disfavored under standard conditions. Predict how an increase in temperature will affect the value of rG. (a) I2(g) 2 I(g) (b) 2 SO2(g) + O2(g) 2 SO3(g) (c) SiCl4(g) + 2 H2O() SiO2(s) + 4 HCl(g) (d) P4(s, white) + 6 H2(g) 4 PH3(g)Heating some metal carbonates, among them magnesium carbonate, leads to their decomposition. MgCO3(s) MgO(s) + CO2(g) (a) Calculate rG and rS for the reaction. (b) Is the reaction product-favored at equilibrium at 298 K? (c) Is the reaction predicted to be product-favored at equilibrium at higher temperatures?Calculate rH and rS for the reaction of tin(IV) oxide with carbon. SnO2(s) + C(s) Sn(s) + CO2(g) (a) Is the reaction product-favored at equilibrium at 298 K? (b) Is the reaction predicted to be product-favored at equilibrium at higher temperatures?The standard free energy change, rG, for the formation of NO(g) from its elements is + 86.58 kJ/mol-rxn at 25 C. Calculate Kp at this temperature for the equilibrium N2(g) + O2(g) NO(g) Comment on the sign of rG and the magnitude of Kp.28PS Calculate rG at 25 C for the formation of 1.00 mol of C2H6(g) from C2H4(g) and H2(g). Use this value to calculate Kp for the equilibrium. C2H4(g) + H2(g) C2H6(g) Comment on the sign of rG and the magnitude of Kp.30PS 31PS 32PS Compare the compounds in each set below and decide which is expected to have the higher entropy. Assume all are at the same temperature. Check your answers using data in Appendix L. (a) HF(g), HCl(g), or HBr(g) (b) NH4Cl(s) or NH4Cl(aq) (c) C2H4(g) or N2(g) (two substances with the same molar mass) (d) NaCl(s) or NaCl(g)Using standard entropy values, calculate rS for the formation of 1.0 mol of NH3(g) from N2(g) and H2(g) at 25 C.About 5 billion kilograms of benzene, C6H6, are made each year. Benzene is used as a starting material for many other compounds and as a solvent (although it is also a carcinogen, and its use is restricted). One compound that can be made from benzene is cyclohexane, C6H12. C6H6() + 3 H2(g) C6H12() rH = 206.7 kJ/mol-rxn; rS = 361.5 J/K mol-rxn Is this reaction predicted to be product-favored at equilibrium at 25 C? Is the reaction enthalpy- or entropy-driven?Hydrogenation, the addition of hydrogen to an organic compound, is an industrially important reaction. Calculate rH, rS, and rG for the hydrogenation of octene, C8H16, to give octane, C8H19 at 25 C. Is the reaction product- or reactant-favored at equilibrium? C8H16(g) + H2(g) C8H18(g) Along with data in Appendix L, the following information is needed for this calculation.Is the combustion of ethane, C2H6, product-favored at equilibrium at 25 C? C2H6(g) + 7/2 O2(g) 2 CO2(g) + 3 H2O(g) Answer the question by calculating the value of S (universe) at 298 K, using values of fH and S in Appendix L. Does the answer agree with your preconceived idea of this reaction?38GQ When vapors from hydrochloric acid and aqueous ammonia come in contact, they react, producing a white cloud of solid NH4C1 (Figure 18.9). HCI(g) + NH3(g) NH4Cl(s) Defining the reactants and products as the system under study: (a) Predict whether S(system), S(surroundings), S(universe), rH, and rG (at 298 K) are greater than zero, equal to zero, or less than zero; and explain your prediction. Verify your predictions by calculating values for each of these quantities. (b) Calculate the value of Kp for this reaction at 298 K.Calculate S(system), S(surroundings), and S(universe) for each of the following processes at 298 K, and comment on how these systems differ. (a) HNO3(g) HNO3(aq) (b) NaOH(s) NaOH(aq)Methanol is now widely used as a fuel in race cars. Consider the following reaction as a possible synthetic route to methanol. C(graphite) + O2(g) + 2 H2(g) CH3OH() Calculate Kp for the formation of methanol at 298 K using this reaction. Would this reaction be more product-favored at a different temperature?The enthalpy of vaporization of liquid diethyl ether, (C2H5)2O, is 26.0 kJ/mol at the boiling point of 35.0 C. Calculate S for a vapor-to-liquid transformation at 35.0 C.Calculate the entropy change, rS, for the vaporization of ethanol, C2H5OH, at its normal boiling point, 78.0 C. The enthalpy of vaporization of ethanol is 39.3 kJ/mol.Using thermodynamic data, estimate the normal boiling point of ethanol. (Recall that liquid and vapor are in equilibrium at 1.0 atm pressure at the normal boiling point.) The actual normal boiling point is 78 C. How well does your calculated result agree with the actual value?45GQ When calcium carbonate is heated strongly, CO2 gas is evolved. The equilibrium pressure of CO2 is 1.00 bar at 897 C, and rH at 298 K is 179.0 kJ/mol-rxn. CaCO3(s) CaO(s) + CO2(g) Estimate the value of rS at 897 C for the reaction.Sodium reacts violently with water according to the equation Na(s) + H2O() NaOH(aq) + H2(g) Without doing calculations, predict the signs of rH and rS for the reaction. Verify your prediction with a calculation.Yeast can produce ethanol by the fermentation of glucose (C6H12O6), which is the basis for the production of most alcoholic beverages. C6H12O6(aq) 2 C2H5OH() + 2 CO2(g) Calculate rH, rS, and rG for the reaction at 25 C. Is the reaction product- or reactant-favored at equilibrium? In addition to the thermodynamic values in Appendix L, you will need the following data for C6H12O6(aq): fH = 1260.0 kl/mol; S = 289 J/K mol; and fG = 918.8 kl/mol.Elemental boron, in the form of thin fibers, can be made by reducing a boron halide with H2. BCl3(g) + 32 H2(g) B(s) + 3 HCl(g) Calculate rH, rS, and rG at 25 C for this reaction. Is the reaction predicted to be product-favored at equilibrium at 25 C? If so, is it enthalpy- or entropy-driven? [S for B(s) is 5.86 J/K mol.]50GQ 51GQ Estimate the boiling point of water in Denver, Colorado (where the altitude is 1.60 km and the atmospheric pressure is 630 mm Hg or 0.840 bar).The equilibrium constant for the butane iso-butane equilibrium at 25 C is 2.50. Calculate rG at this temperature in units of kJ/mol.A crucial reaction for the production of synthetic fuels is the production of H2 by the reaction of coal with steam. The chemical reaction is C(s) + H2O(g) CO(g) + H2(g) (a) Calculate rG for this reaction at 25 C, assuming C(s) is graphite. (b) Calculate Kp for the reaction at 25 C. (c) Is the reaction predicted to be product-favored at equilibrium at 25 C? If not, at what temperature will it become so?Calculate rG for the decomposition of sulfur trioxide to sulfur dioxide and oxygen. 2 SO3(g) 2 SO2(g) + O2(g) (a) Is the reaction product-favored at equilibrium at 25 C? (b) If the reaction is not product-favored at 25 C, is there a temperature at which it will become so? Estimate this temperature. (c) Estimate the equilibrium constant for the reaction at 1500 C.56GQ A cave in Mexico was recently discovered to have some interesting chemistry. Hydrogen sulfide, H2S, reacts with oxygen in the cave to give sulfuric acid, which drips from the ceiling in droplets with a pH less than 1. The reaction occurring is H2S(g) + 2 O2(g) H2SO4() Calculate rH, rS, and rG. Is the reaction product-favored at equilibrium at 25 C? Is it enthalpy- or entropy-driven?Wet limestone is used to scrub SO2 gas from the exhaust gases of power plants. One possible reaction gives hydrated calcium sulfite: CaCO3(s) + SO2(g) + H2O() CaSO3 H2O(s) + CO2(g) Another reaction gives hydrated calcium sulfate: CaCO3(s) + SO2(g) + H2O() + O2(g) CaSO4 H2O(s) + CO2(g) (a) Which reaction is more product-favored at equilibrium? Use the data in the table below and any other information needed in Appendix L to calculate rG for each reaction at 25 C. (b) Calculate rG for the reaction CaSO3 H2O(s) + O2(g) CaSO4 H2O(s) Is this reaction product- or reactant-favored at equilibrium?Sulfur undergoes a phase transition between 80 and 100 C. S8(rhombic) S8(monoclinic) rH = 3.213 kl/mol-rxn rS = 8.7 J/K mol-rxn (a) Estimate rG for the transition at 80.0 C and 110.0 C. What do these results tell you about the stability of the two forms of sulfur at each of these temperatures? (b) Calculate the temperature at which rG = 0. What is the significance of this temperature?Calculate the entropy change for dissolving HCl gas in water at 25 C. Is the sign of rS what you expected? Why or why not?Some metal oxides can be decomposed to the metal and oxygen under reasonable conditions. Is the decomposition of silver(I) oxide product-favored at equilibrium at 25 C? 2 Ag2O(s) 4 Ag(s) + O2(g) If not, can it become so if the temperature is raised? At what temperature does the reaction become product-favored at equilibrium?62IL 63IL 64IL Titanium(IV) oxide is converted to titanium carbide with carbon at a high temperature. TiO2(s) + 3 C(s) 2 CO(g) + TiC(s) (a) Calculate rG and K at 727 C. (b) Is the reaction product-favored at equilibrium at this temperature? (c) How can the reactant or product concentrations be adjusted for the reaction to proceed at 727 C?Cisplatin [cis-diamminedichloroplatinum(II)] is a potent treatment for certain types of cancers, but the trans isomer is not effective. What is the equilibrium constant at 298 K for the transformation of the cis to the trans isomer? Which is the favored isomer at 298 K, the cis or the trans isomer?67SCQ Explain why each of the following statements is incorrect. (a) Entropy increases in all spontaneous reactions. (b) Reactions with a negative free energy change (rG 0) are product-favored and occur with rapid transformation of reactants to products. (c) All spontaneous processes are exothermic. (d) Endothermic processes are never spontaneous.Decide whether each of the following statements is true or false. If false, rewrite it to make it true. (a) The entropy of a substance increases on going from the liquid to the vapor state at any temperature. (b) An exothermic reaction will always be spontaneous. (c) Reactions with a positive rH and a positive rS can never be product-favored. (d) If rG for a reaction is negative, the reaction will have an equilibrium constant greater than 1.Under what conditions is the entropy of a pure substance 0 J/K mol? Could a substance at standard conditions at 25 C have a value of 0 J/K mol? A negative entropy value? Are there any conditions under which a substance will have negative entropy? Explain your answer.71SCQ Consider the formation of NO(g) from its elements. N2(g) + O2(g) 2 NO(g) (a) Calculate Kp at 25 C. Is the reaction product-favored at equilibrium at this temperature? (b) Assuming rH and rS are nearly constant with temperature, calculate rG at 700 C. Estimate Kp from the new value of rG at 700 C. Is the reaction product-favored at equilibrium at 700 C? (c) Using Kp at 700 C, calculate the equilibrium partial pressures of the three gases if you mix 1.00 bar each of N2 and O2.73SCQ The normal melting point of benzene, C6H6, is 5.5 C. For the process of melting, what is the sign of each of the following? (a) rH (b) rS (c) rG at 5.5 C (d) rSG at 0.0 C (e) rG at 25.0 C 75SCQ For each of the following processes, predict the algebraic sign of rH, rS, and rG. No calculations are necessary; use your common sense. (a) The decomposition of liquid water to give gaseous oxygen and hydrogen, a process that requires a considerable amount of energy. (b) Dynamite is a mixture of nitroglycerin, C3H5N3O9, and diatomaceous earth. The explosive decomposition of nitroglycerin gives gaseous products such as water, CO2, and others; much heat is evolved. (c) The combustion of gasoline in the engine of your car, as exemplified by the combustion of octane. 2 C8H18(g) + 25 O2(g) 16 CO2(g) + 18 H2O(g)Heater Meals are food packages that contain their own heat source, lust pour water into the heater unit, wait a few minutes, and voila! You have a hot meal. Mg(s) + 2 H2O() Mg(OH)2(s) + H2(g) (a) Confirm that this is a product-favored reaction at equilibrium at 25 C. (b) What mass of magnesium is required to produce sufficient energy to heat 225 mL of water (density = 0.995 g/mL) from 25 C to the boiling point?78SCQ 79SCQ 80SCQ Iodine, I2, dissolves readily in carbon tetrachloride. For this process, H = 0 kJ/mol. I2(s) I2 (in CCl4 solution) What is the sign of rG? Is the dissolving process entropy-driven or enthalpy-driven? Explain briefly.82SCQ 83SCQ 84SCQ 85SCQ 86SCQ The Haber-Bosch process for the production of ammonia is one of the key industrial processes in developed countries. N2(g) + 3H2(g) 2NH3(g) (a) Calculate rG for the reaction at 298 K, 800 K, and 1300 K. Data at 298 K are given in Appendix L Data for the other temperatures are as follows: How does the rG change with temperature? (b) Calculate the equilibrium constant for the reaction at 298 K, 800 K, and 1300 K. (c) At what temperature (298 K, 800 K, or 1300 K) is the mole fraction of NH3 the greatest?88SCQ 2CYU 3CYU 1. Copper(II) sulfide reacts with nitric acid according to the balanced equation: 3 CuS(s) + 8 H+(aq) + 2 NO3−(aq) 3 Cu2+(aq) + 3 S(s) + 4 H2O(ℓ) + 2 NO(g) The substance oxidized is CuS H+ NO3− 2RC The balanced half-reaction for Br2 BrO3 in basic solution is (a) 3 OH + Br2 2BrO3+ H2O + e (b) 12 OH + Br2 2 BrO3 + 6 H2O + 10 e (c) e + OH + Br2 2 BrO3 + H2O (d) l0e + Br2 + 6H2O 2BrO3 +6OH Describe how to set up a voltaic cell using the following half-reactions: Reduction half-reaction:Ag+(aq) + e Ag(s) Oxidation half-reaction:Ni(s) Ni2+(aq) + 2 e Which electrode is the anode, and which is the cathode? What is the overall cell reaction? What is the direction of electron flow in an external wire connecting the two electrodes? Describe the ion flow in a salt bridge (with NaNO3) connecting the cell compartments.The following overall chemical reaction occurs in an electrochemical cell. Overall chemical equation: Zn(s) + PbSO4(s) Zn2+(aq) + Pb(s) + SO42(aq) Use cell notation to describe the electrochemical cell.1RC 2RC 3RC 1RC 2RC (a) Rank the following metals in their ability to function as reducing agents: Hg, Sn, and Pb. (b) Which halogens will oxidize mercury to mercury(II)?1RC 2RC 3RC A voltaic cell is set up with an aluminum electrode in a 0.025 M Al(NO3)3(aq) solution and an iron electrode in a 0.50 M Fe(NO3)2(aq) solution. Determine the cell potential, Ecell, at 298 K.Check Your Understanding The half-cells Fe2+(aq, 0.024 M)|Fe(s) and H+(aq, 0.056 M)|H2(1.0 bar) are linked by a salt bridge to create a voltaic cell. Determine the cell potential, Ecells at 298 K. 1RC 1CYU Calculate the equilibrium constant at 25 C for the reaction 2 Ag+(aq) + Hg() 2 Ag(s) + Hg2+(aq)1RC Predict the chemical reactions that will occur at the two electrodes in the electrolysis of an aqueous sodium hydroxide solution.1RC 1CYU 1. If you wish to convert 0.0100 mol of Au3+ (aq) ions into Au(s) in a “gold-plating” process, how long must you electrolyze a solution if the current passing through the circuit is 2.00 amps? 483 seconds 4.83 104 seconds 965 seconds 1450 seconds 1Q 2Q 3Q 1Q Use standard reduction potentials to determine which of the following metals could serve as a sacrificial anode on a copper-sheathed hull. Indicate all correct responses. a. tin b. silver c. iron d. nickel e. chromium 3Q The overall reaction for the production of Cu(OH)2 from Cu in oxygenated water can be broken into three steps: an oxidation half-reaction, a reduction half-reaction, and a precipitation reaction. a. Complete and balance the two missing half-reactions to give the overall equation for the oxidation of cooper in seawater. Oxidation half-reaction: ? Reduction half-reaction: ? Precipitation:Cu2+(aq)+2OH(aq)Cu(OH)2(s)Overall:Cu(s)+12O2(g)+H2O(l)Cu(OH)2(s) b. Determine the equilibrium constant for the overall reaction at 25 C using standard reduction potentials and the solubility product constant (Ksp) of Cu(OH)2(s).Assume the following electrochemical cell simulates the galvanic cell formed by copper and zinc in seawater at pH 7.90 and 25 C. Zn | Zn(OH)2(s) | OH(aq) || Cu(OH)2(s) | Cu(s) a. Write a balanced equation for the reaction that occurs at the cathode. b. Write a balanced equation for the reaction that occurs at the anode. c. Write a balanced chemical equation for the overall reaction. d. Determine the potential (in volts) of the cell.Write balanced equations for the following half-reactions. Specify whether each is an oxidation or reduction. (a) Cr(s) Cr3+(aq)(in acid) (b) AsH3(g) As(s)(in acid) (c) VO3(aq) V2+(aq)(in acid) (d) Ag(s) Ag2O(s)(in base)Write balanced equations for the following half-reactions. Specify whether each is an oxidation or reduction. (a) H2O2(aq) O2(g)(in acid) (b) H2C2O4(aq) CO2(g)(in acid) (c) NO3(aq) NO(g)(in acid) (d) MnO4(aq) MnO2(s)(in base)Balance the following redox equations. All occur in acid solution. (a) Ag(s) + NO3(aq) NO2(g) + Ag+(aq) (b) MnO4 (aq) + HSO3(aq) Mn2+ (aq) + SO42(aq) (c) Zn(s) + NO3(aq) Zn2+(aq) + N2O(g) (d) Cr(s) + NO3(aq) Cr3+(aq) + NO(g)Balance the following redox equations. All occur in acid solution. (a) Sn(s) + H+(aq) Sn2+(aq) + H2(g) (b) Cr2O72 (aq) + Fe2+(aq) Cr3+(aq) + Fe3+(aq) (c) MnO2(s) + Cl(aq) Mn2+(aq) + Cl2(g) (d) CH2O(aq) + Ag+(aq) HCO2H(aq) + Ag(s)Balance the following redox equations. All occur in basic solution. (a) Al(s) + H2O() Al(OH)4(aq) + H2(g) (b) CrO42 (aq) + SO32(aq) Cr(OH)3(s) + SO42(aq) (c) Zn(s) + Cu(OH)2(s) [Zn(OH)4]2(aq) + Cu(s) (d) HS (aq) + ClO3 (aq) S(s) + Cl (aq)6PS A voltaic cell is constructed using the reaction of chromium metal and iron(II) ions. 2 Cr(s) + 3 Fe2+(aq) 2 Cr3+(aq) + 3 Fe(s) Complete the following sentences: Electrons in the external circuit flow from the ________ electrode to the ______ electrode. Negative ions move in the salt bridge from the ________ half-cell to the ______ half-cell. The half-reaction at the anode is _______ and that at the cathode is ________.A voltaic cell is constructed using the reaction Mg(s) + 2H+(aq) Mg2+(aq) + H2(g) (a) Write equations for the oxidation and reduction half-reactions. (b) Which half-reaction occurs in the anode compartment, and which occurs in the cathode compartment? (c) Complete the following sentences: Electrons in the external circuit flow from the ________ electrode to the ______ electrode. Negative ions move in the salt bridge from the ______ half-cell to the ______ half-cell. The half-reaction at the anode is ____, and that at the cathode is _____.The half-cells Fe2+(aq) | Fe(s) and O2(g) | H2O (in and solution) are linked to create a voltaic cell. (a) Write equations for the oxidation and reduction half-reactions and for the overall (cell) reaction. (b) Which half-reaction occurs in the anode compartment, and which occurs in the cathode compartment? (c) Complete the following sentences: Electrons in the external circuit flow from the _______ electrode to the _____ electrode. Negative ions move in the salt bridge from the _____ half-cell to the ______ half-cell.The half cells Sn2+(aq) |Sn(s) and Cl2(g) |Cl(aq) are linked to create a voltaic cell. (a) Write equations for the oxidation and reduction half-reactions and for the overall (cell) reaction. (b) Which half-reaction occurs in the anode compartment, and which occurs in the cathode compartment? (c) Complete the following sentences: Electrons in the external circuit flow from the ______ electrode to the ____ electrode. Negative ions move in the salt bridge from the _____ half-cell to the _____ half-cell.For each of the following electrochemical cells, write equations for the oxidation and reduction half-reactions and for the overall reaction. (a) Cu(s)|Cu2+(aq)||Fe3+(aq), Fe2+(aq)|Pt(s) (b) Pb(s)|PbSO4(s)|SO42(aq)||Fe3+(aq), Fe2+(aq)|Pt(s)For each of the following electrochemical cells, write equations for lire oxidation and reduction half-reactions and for the overall reaction (a) Pb(s)|Pb2+(aq)||Sn4+(aq),Sn2+(aq)|C(s) (b) Hg()|Hg2Cl2(s)|Cl(aq)||Ag+(aq)|Ag(s)Use cell notation to depict an electrochemical cell based upon the following reaction that is product-favored at equilibrium. Cu(s) + Cl2(g) 2 Cl(aq) + Cu2+(aq)Use cell notation to depict an electrochemical cell based upon the following reaction that is product-favored at equilibrium. Fe3+(aq) + Ag(s) + Cl(aq) Fe2+(aq) + AgCl(s)What are the similarities and differences between dry cells, alkaline batteries, and Ni-cad batteries?

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