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engineering
the science and engineering of materials
Chemistry 10th Edition Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste - Solutions
You want to “plate out” nickel metal from a nickel nitrate solution onto a piece of metal inserted into the solution. Should you use copper or zinc? Explain.
A copper penny can be dissolved in nitric acid but not in hydro chloric acid. Using reduction potentials from the book, show why this is so. What are the products of the reaction? Newer pennies contain a mixture of zinc and copper. What happens to the zinc in the penny when the coin is placed in
Consider the dissociation of a weak acid HA (Ka = 4.5 × 10-3) in water:Calculate ΔGο for this reaction at 25οC. HA (aq) H+ (aq) + A¯(aq)
For the equilibrium the initial concentrations are PA = PB = PC = 0.100 atm. Once equilibrium has been established, it is found that PC = 0.040 atm. What is ΔGο for this reaction at 25οC? A(g) + 2B(g)C(g)
Consider two perfectly insulated vessels. Vessel 1 initially contains an ice cube at 0οC and water at 0οC. Vessel 2 initially contains an ice cube at 0οC and a saltwater solution at 0οC. Consider the process H2O(s) → H2O(l) .a. Determine the sign of ΔS, ΔSsurr, and ΔSuniv for the process
What is a redox reaction? Is the substance reduced the oxidizing agent or the reducing agent? How about the substance oxidized? Explain. What is a half-reaction? Why must the number of electrons lost in the oxidation half-reaction equal the number of electrons gained in the reduction half-reaction
In the electrolysis of a sodium chloride solution, what volume of H2(g) is produced in the same time it takes to produce 257 L Cl2(g), with both volumes measured at 50.οC and 2.50 atm?
Consider a galvanic cell based on the following theoretical half-reactions: What is the value of ΔGο and K for this cell? M4+ + 4e→→→→→M N³+ + 3e N 8° (V) 0.66 0.39
When the environment is contaminated by a toxic or potentially toxic substance (for example, from a chemical spill or the use of insecticides), the substance tends to disperse. How is this consistent with the second law of thermodynamics? In terms of the second law, which requires the least work:
Entropy has been described as “time’s arrow.” Interpret this view of entropy.
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 × 10-3 M Cu(NH3)42+. The equilibrium between Cu2+ and NH3
Even if ΔG is negative, the reaction may not occur. Explain the interplay between the thermodynamics and the kinetics of a reaction. High temperatures are favorable to a reaction kinetically but may be unfavorable to a reaction thermodynamically. Explain.
Is ΔSsurr favorable or unfavorable for exothermic reactions? Endothermic reactions? Explain.
What types of experiments can be carried out to determine whether a reaction is spontaneous? Does spontaneity have any relationship to the final equilibrium position of a reaction? Explain.
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
What is the second law of thermodynamics? For any process, there are four possible sign combinations for ΔSsys and ΔSsurr. Which sign combination(s) always give a spontaneous process? Which sign combination(s) always give a non spontaneous process? Which sign combination(s) may or may not give a
For a liquid, which would you expect to be larger, ΔSfusion or ΔSevaporation? Why?
A 0.400-M solution of ammonia was titrated with hydrochloric acid to the equivalence point, where the total volume was 1.50 times the original volume. At what pH does the equivalence point occur?
Carbon tetrachloride (CCl4) and benzene (C6H6) form ideal solutions. Consider an equimolar solution of CCl4 and C6H6 at 25οC. The vapor above the solution is collected and condensed. Using the following data, determine the composition in mole fraction of the condensed vapor.
Sodium chloride is added to water (at 25οC) until it is saturated. Calculate the Cl- concentration in such a solution. Species NaCl(s) Na + (aq) Cl- (aq) AG (kJ/mol) -384 -262 - 131
The vaporization of ethanol at its normal boiling point, 351 K, has ΔS = 110. J/K · mol. Calculate ΔE for the vaporization process at 1 atm and 351 K. C₂H5OH(1)→ C₂H5OH(g)
Consider a weak acid, HX. If a 0.10-M solution of HX has a pH of 5.83 at 25οC, what is ΔGο for the acid’s dissociation reaction at 25οC?
Some nonelectrolyte solute (molar mass = 142 g/mol) was dissolved in 150. mL of a solvent (density = 0.879 g/cm3). The elevated boiling point of the solution was 355.4 K. What mass of solute was dissolved in the solvent? For the solvent, the enthalpy of vaporization is 33.90 kJ/mol, the entropy of
What is meant by the presence of a common ion? How does the presence of a common ion affect an equilibrium such asWhat is an acid–base solution called that contains a common ion? HNO₂ (aq) →H+ (aq) + NO₂ (aq)
What are the major species in solution after NaHSO4 is dissolved in water? What happens to the pH of the solution as more NaHSO4 is added? Why? Would the results vary if baking soda (NaHCO3) were used instead?
Mixing together solutions of acetic acid and sodium hydroxide can make a buffered solution. Explain. How does the amount of each solution added change the effectiveness of the buffer?
A good buffer generally contains relatively equal concentrations of weak acid and conjugate base. If you wanted to buffer a solution at pH = 4.00 or pH = 10.00, how would you decide which weak acid– conjugate base or weak base–conjugate acid pair to use? The second characteristic of a good
Sketch two pH curves, one for the titration of a weak acid with a strong base and one for a strong acid with a strong base. How are they similar? How are they different? Account for the similarities and the differences.
Sketch a pH curve for the titration of a weak acid (HA) with a strong base (NaOH). List the major species, and explain how you would go about calculating the pH of the solution at various points, including the halfway point and the equivalence point.
You have a solution of the weak acid HA and add some of the salt NaA to it. What are the major species in the solution? What do you need to know to calculate the pH of the solution, and how would you use this information? How does the pH of the solution of just the HA compare with that of the final
Why does an indicator change from its acid color to its base color over a range of pH values? In general, when do color changes start to occur for indicators? Can the indicator thymol blue contain only a single -CO2H group and no other acidic or basic functional group? Explain.
Sketch the titration curves for a diprotic acid titrated by a strong base and a triprotic acid titrated by a strong base. List the major species present at various points in each curve. In each curve, label the halfway points to equivalence. How do you calculate the pH at these halfway points?
Consider the following two acids: In two separate experiments the pH was measured during the titration of 5.00 mmol of each acid with 0.200 M NaOH. Each experiment showed only one stoichiometric point when the data were plotted. In one experiment the stoichiometric point was at 25.00 mL added
The common ion effect for weak acids is to significantly decrease the dissociation of the acid in water. Explain the common ion effect.
Consider a buffer solution where [weak acid] > [conjugate base]. How is the pH of the solution related to the pKa value of the weak acid? If [conjugate base] > [weak acid], how is pH related to pKa?
A best buffer has about equal quantities of weak acid and conjugate base present as well as having a large concentration of each species present. Explain.
Acid–base indicators mark the end point of titrations by “magically” turning a different color. Explain the “magic” behind acid–base indicators.
Which of the following can be classified as buffer solutions? a. 0.25 M HBr + 0.25 M HOBrb. 0.15 M HClO4 + 0.20 M RbOHc. 0.50 M HOCl + 0.35 M KOCld. 0.70 M KOH + 0.70 M HONH2e. 0.85 M H2NNH2 + 0.60 M H2NNH3NO3
A buffer is prepared by dissolving HONH2 and HONH3NO3 in some water. Write equations to show how this buffer neutralizes added H+ and OH-.
Calculate the pH after 0.020 mole of NaOH is added to 1.00 L of each of the solutions in Exercise 26. Data in Exercise 26.Calculate the pH of each of the following solutions.a. 0.100 M HONH2 (Kb = 1.1 × 10-8)b. 0.100 M HONH3Clc. Pure H2Od. A mixture containing 0.100 M HONH2 and 0.100 M
Which of the solutions in Exercise 26 is a buffered solution? Data in Exercise 26.Calculate the pH of each of the following solutions.a. 0.100 M HONH2 (Kb = 1.1 × 10-8)b. 0.100 M HONH3Clc. Pure H2Od. A mixture containing 0.100 M HONH2 and 0.100 M HONH3Cl
Calculate the pH of a solution that is 0.60 M HF and 1.00 M KF.
A buffered solution is made by adding 50.0 g NH4Cl to 1.00 L of a 0.75-M solution of NH3. Calculate the pH of the final solution. (Assume no volume change.)
What volumes of 0.50 M HNO2 and 0.50 M NaNO2 must be mixed to prepare 1.00 L of a solution buffered at pH = 3.55?
Calculate the ratio [NH3]/[NH4+] in ammonia/ammonium chloride buffered solutions with the following pH values:a. pH = 9.00b. pH = 8.80c. pH = 10.00d. pH = 9.60
Calculate the pH of a solution that is 0.40 M H2NNH2 and 0.80 M H2NNH3NO3. In order for this buffer to have pH = pKa, would you add HCl or NaOH? What quantity (moles) of which reagent would you add to 1.0 L of the original buffer so that the resulting solution has pH = pKa?
Calculate the pH of a solution that is 0.20 M HOCl and 0.90 M KOCl. In order for this buffer to have pH = pKa, would you add HCl or NaOH? What quantity (moles) of which reagent would you add to 1.0 L of the original buffer so that the resulting solution has pH = pKa?
Which of the following mixtures would result in buffered solutions when 1.0 L of each of the two solutions are mixed? a. 0.1 M KOH and 0.1 M CH3NH3Clb. 0.1 M KOH and 0.2 M CH3NH2c. 0.2 M KOH and 0.1 M CH3NH3Cld. 0.1 M KOH and 0.2 M CH3NH3Cl
Which of the following mixtures would result in a buffered solution when 1.0 L of each of the two solutions are mixed? a. 0.2 M HNO3 and 0.4 M NaNO3b. 0.2 M HNO3 and 0.4 M HFc. 0.2 M HNO3 and 0.4 M NaFd. 0.2 M HNO3 and 0.4 M NaOH
What quantity (moles) of NaOH must be added to 1.0 L of 2.0 M HC2H3O2 to produce a solution buffered at each pH?a. PH = pKab. PH = 4.00c. PH = 5.00
Consider the titration of 40.0 mL of 0.200 M HClO4 by 0.100 M KOH. Calculate the pH of the resulting solution after the following volumes of KOH have been added.a. 0.0 mLb. 10.0 mLc. 40.0 mLd. 80.0 mLe. 100.0 mL
Consider the titration of 80.0 mL of 0.100 M Ba(OH)2 by 0.400 M HCl. Calculate the pH of the resulting solution after the following volumes of HCl have been added.a. 0.0 mLb. 20.0 mLc. 30.0 mLd. 40.0 mLe. 80.0 mL
Consider the titration of 100.0 mL of 0.200 M acetic acid (Ka = 1.8 × 10-5) by 0.100 M KOH. Calculate the pH of the resulting solution after the following volumes of KOH have been added.a. 0.0 mLb. 50.0 mLc. 100.0 mLd. 150.0 mLe. 200.0 mLf. 250.0 mL
Methyl red has the following structure: It undergoes a color change from red to yellow as a solution gets more basic. Calculate an approximate pH range for which methyl red is useful. What is the color change and the pH at the color change when a weak acid is titrated with a strong base using
Consider the titration of 100.0 mL of 0.100 M H2NNH2 (Kb = 3.0 × 10-6) by 0.200 M HNO3. Calculate the pH of the resulting solution after the following volumes of HNO3 have been added.a. 0.0 mLb. 20.0 mLc. 25.0 mLd. 40.0 mLe. 50.0 mLf. 100.0 mL
Potassium hydrogen phthalate, known as KHP (molar mass = 204.22 g/mol), can be obtained in high purity and is used to determine the concentration of solutions of strong bases by the reactionIf a typical titration experiment begins with approximately 0.5 g KHP and has a final volume of about 100 mL,
In the titration of 50.0 mL of 1.0 M methylamine, CH3NH2 (Kb = 4.4 × 10-4), with 0.50 M HCl, calculate the pH under the following conditions. a. After 50.0 mL of 0.50 M HCl has been addedb. At the stoichiometric point
a. Calculate the pH of a buffered solution that is 0.100 M in C6H5CO2H (benzoic acid, Ka = 6.4 × 10-5) and 0.100 M in C6H5CO2Na.b. Calculate the pH after 20.0% (by moles) of the benzoic acid is converted to benzoate anion by addition of a strong base. Use the dissociation equilibriumto calculate
A student dissolves 0.0100 mol of an unknown weak base in 100.0 mL water and titrates the solution with 0.100 M HNO3. After 40.0 mL of 0.100 M HNO3 was added, the pH of the resulting solution was 8.00. Calculate the Kb value for the weak base.
Amino acids are the building blocks for all proteins in our bodies. A structure for the amino acid alanine isAll amino acids have at least two functional groups with acidic or basic properties. In alanine, the carboxylic acid group has Ka = 4.5 × 10-3 and the amino group has Kb = 7.4 × 10-5.
Derive an equation analogous to the Henderson–Hasselbalch equation but relating pOH and pKb of a buffered solution composed of a weak base and its conjugate acid, such as NH3 and NH4+.
You make 1.00 L of a buffered solution (pH = 4.00) by mixing acetic acid and sodium acetate. You have 1.00 M solutions of each component of the buffered solution. What volume of each solution do you mix to make such a buffered solution?
One method for determining the purity of aspirin (C9H8O4) is to hydrolyze it with NaOH solution and then to titrate the remaining NaOH. The reaction of aspirin with NaOH is as follows:A sample of aspirin with a mass of 1.427 g was boiled in 50.00 mL of 0.500 M NaOH. After the solution was cooled,
What quantity (moles) of HCl(g) must be added to 1.0 L of 2.0 M NaOH to achieve a pH of 0.00? (Neglect any volume changes.)
Calculate the volume of 1.50 × 10-2 M NaOH that must be added to 500.0 mL of 0.200 M HCl to give a solution that has pH = 2.15.
A certain acetic acid solution has pH = 2.68. Calculate the volume of 0.0975 M KOH required to reach the equivalence point in the titration of 25.0 mL of the acetic acid solution.
A 0.210-g sample of an acid (molar mass = 192 g/mol) is titrated with 30.5 mL of 0.108 M NaOH to a phenolphthalein end point. Is the acid monoprotic, diprotic, or triprotic?
A student intends to titrate a solution of a weak monoprotic acid with a sodium hydroxide solution but reverses the two solutions and places the weak acid solution in the buret. After 23.75 mL of the weak acid solution has been added to 50.0 mL of the 0.100 M NaOH solution, the pH of the resulting
A student titrates an unknown weak acid, HA, to a pale pink phenolphthalein end point with 25.0 mL of 0.100 M NaOH. The student then adds 13.0 mL of 0.100 M HCl. The pH of the resulting solution is 4.70. How is the value of pKa for the unknown acid related to 4.70?
A sample of a certain monoprotic weak acid was dissolved in water and titrated with 0.125 M NaOH, requiring 16.00 mL to reach the equivalence point. During the titration, the pH after adding 2.00 mL NaOH was 6.912. Calculate Ka for the weak acid.
Calculate the pH of a solution formed by mixing 100.0 mL of 0.100 M NaF and 100.0 mL of 0.025 M HCl.
What concentration of NH4Cl is necessary to buffer a 0.52-M NH3 solution at pH = 9.00? (Kb for NH3 = 1.8 × 10-5.)
Consider a buffered solution containing CH3NH3Cl and CH3NH2. Which of the following statements concerning this solution is(are) true? (Ka for CH3NH3+ = 2.3 × 10-11.)a. A solution consisting of 0.10 M CH3NH3Cl and 0.10 M CH3NH2 would have a greater buffering capacity than one containing 1.0 M
Consider the titration of 100.0 mL of 0.100 M HCN by 0.100 M KOH at 25οC. (Ka for HCN = 6.2 × 10-10.)a. Calculate the pH after 0.0 mL of KOH has been added.b. Calculate the pH after 50.0 mL of KOH has been added. c. Calculate the pH after 75.0 mL of KOH has been added. d. Calculate the
Consider a solution formed by mixing 50.0 mL of 0.100 M H2SO4, 30.0 mL of 0.100 M HOCl, 25.0 mL of 0.200 M NaOH, 25.0 mL of 0.100 M Ba(OH)2, and 10.0 mL of 0.150 M KOH. Calculate the pH of this solution.
A buffer is made using 45.0 mL of 0.750 M HC3H5O2 (Ka = 1.3 × 10-5) and 55.0 mL of 0.700 M NaC3H5O2. What volume of 0.10 M NaOH must be added to change the pH of the original buffer solution by 2.5%?
A few drops of each of the indicators shown in the accompanying table were placed in separate portions of a 1.0-M solution of a weak acid, HX. The results are shown in the last column of the table. What is the approximate pH of the solution containing HX? Calculate the approximate value of Ka for
A 10.00-g sample of the ionic compound NaA, where A- is the anion of a weak acid, was dissolved in enough water to make 100.0 mL of solution and was then titrated with 0.100 M HCl. After 500.0 mL HCl was added, the pH was 5.00. The experimenter found that 1.00 L of 0.100 M HCl was required to reach
Calculate the pH of a solution prepared by mixing 250. mL of 0.174 m aqueous HF (density = 1.10 g/mL) with 38.7 g of an aqueous solution that is 1.50% NaOH by mass (density = 1.02 g/mL). (Ka for HF = 7.2 × 10-4.)
You are browsing through the Handbook of Hypothetical Chemistry when you come across a solid that is reported to have a Ksp value of zero in water at 25οC. What does this mean?
List some salts whose solubility increases as the pH becomes more acidic. What is true about the anions in these salts? List some salts whose solubility remains unaffected by the solution pH. What is true about the anions in these salts?
Solubility is an equilibrium position, whereas Ksp is an equilibrium constant. Explain the difference.
Malonic acid (HO2CCH2CO2H) is a diprotic acid. In the titration of malonic acid with NaOH, stoichiometric points occur at pH = 3.9 and 8.8. A 25.00-mL sample of malonic acid of unknown concentration is titrated with 0.0984 M NaOH, requiring 31.50 mL of the NaOH solution to reach the
A buffer solution is prepared by mixing 75.0 mL of 0.275 M fluorobenzoic acid (C7H5O2F) with 55.0 mL of 0.472 M sodium fluorobenzoate. The pKa of this weak acid is 2.90. What is the pH of the buffer solution?
Consider a solution prepared by mixing the following:50.0 mL of 0.100 M Na3PO4100.0 mL of 0.0500 M KOH200.0 mL of 0.0750 M HCl50.0 mL of 0.150 M NaCNDetermine the volume of 0.100 M HNO3 that must be added to this mixture to achieve a final pH value of 7.21.
Explain the following phenomenon: You have a test tube with an aqueous solution of silver nitrate as shown in test tube 1 below. A few drops of aqueous sodium chromate solution was added with the end result shown in test tube 2. A few drops of aqueous sodium chloride solution was then added with
Which of the following will affect the total amount of solute that can dissolve in a given amount of solvent? a. The solution is stirred.b. The solute is ground to fine particles before dissolving.c. The temperature changes.
Devise as many ways as you can to experimentally determine the Ksp value of a solid. Explain why each of these would work.
What is a common ion and how does its presence affect the solubility?
A friend tells you: “The constant Ksp of a salt is called the solubility product constant and is calculated from the concentrations of ions in the solution. Thus, if salt A dissolves to a greater extent than salt B, salt A must have a higher Ksp than salt B.” Do you agree with your friend?
What happens to the Ksp value of a solid as the temperature of the solution changes? Consider both increasing and decreasing temperatures, and explain your answer.
Which is more likely to dissolve in an acidic solution, silver sulfide or silver chloride? Why?
When 5 M ammonia is added to a solution containing Cu(OH)2(s), the precipitate will eventually dissolve in solution. Why? If 5 M HNO3 is then added, the Cu(OH)2 precipitate re-forms. Why? In general, what effect does the ability of a cation to form a complex ion have on the solubility of salts
Sodium chloride is listed in the solubility rules as a soluble compound. Therefore, the Ksp value for NaCl is infinite. Is this statement true or false? Explain.
When Na3PO4(aq) is added to a solution containing a metal ion and a precipitate forms, the precipitate generally could be one of two possibilities. What are the two possibilities?
The common ion effect for ionic solids (salts) is to significantly decrease the solubility of the ionic compound in water. Explain the common ion effect.
Sulfide precipitates are generally grouped as sulfides insoluble in acidic solution and sulfides insoluble in basic solution. Explain why there is a difference between the two groups of sulfide precipitates.
List some ways one can increase the solubility of a salt in water.
The stepwise formation constants for a complex ion usually have values much greater than 1. What is the significance of this?
Silver chloride dissolves readily in 2 M NH3 but is quite insoluble in 2 M NH4NO3. Explain.
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