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Problem 121
Neither strontium (Sr) nor antimony (Sb) is shown in the activity series of Table 4.5. Based on their positions in the periodic table, which would you expect to be the better reducing agent? Will the following reaction occur? Explain.
Problem 122a
(a) Use the following reactions to arrange the elements A, B, C, and D in order of their decreasing ability as reducing agents:
Problem 122b
(b) Which of the following reactions would you expect to occur according to the activity series you established in part (a)?
Problem 123a
(a) Use the following reactions to arrange the elements A, B, C, and D in order of their decreasing ability as reducing agents:
Problem 123b
(b) Which of the following reactions would you expect to occur according to the activity series you established in part (a)?
- Iodine, I2, reacts with aqueous thiosulfate ion in neutral solution according to the balanced equation How many grams of I2 are present in a solution if 35.20 mL of 0.150 M Na2S2O3 solution is needed to titrate the I2 solution?
Problem 124
- How many milliliters of 0.250 M Na2S2O3 solution is needed for complete reaction with 2.486 g of I2 according to the equation in Problem 4.124?
Problem 125
- Dichromate ion, Cr2O7 2-, reacts with aqueous iron(II) ion in acidic solution according to the balanced equation What is the concentration of Fe2+ if 46.99 mL of 0.2004 M K2Cr2O7 is needed to titrate 50.00 mL of the Fe2+ solution?
Problem 126
- A volume of 18.72 mL of 0.1500 M K2Cr2O7 solution was required to titrate a sample of FeSO4 according to the equation in Problem 4.126. What is the mass of the sample?
Problem 127
- What is the molar concentration of As(III) in a solution if 22.35 mL of 0.100 M KBrO3 is needed for complete reaction with 50.00 mL of the As(III) solution? The balanced equation is:
Problem 128
- Standardized solutions of KBrO3 are frequently used in redox titrations. The necessary solution can be made by dissolving KBrO3 in water and then titrating it with an As(III) solution. What is the molar concentration of a KBrO3 solution if 28.55 mL of the solution is needed to titrate 1.550 g of As2O3? See Problem 4.128 for the balanced equation. (As2O3 dissolves in aqueous acid solution to yield H3AsO3: As2O3 + 3 H2OS 2 H3AsO3.)
Problem 129
- The metal content of iron in ores can be determined by a redox procedure in which the sample is first oxidized with Br2 to convert all the iron to Fe3+ and then titrated with Sn2+ to reduce the Fe3+ to Fe2+. The balanced equation is: What is the mass percent Fe in a 0.1875 g sample of ore if 13.28 mL of a 0.1015 M Sn2+ solution is needed to titrate the Fe3+?
Problem 130
- The concentration of the Sn2+ solution used in Problem 4.130 can be found by letting it react with a known amount of Fe2+. What is the molar concentration of an Sn2+ solution if 23.84 mL is required for complete reaction with 1.4855 g of Fe2O3?
Problem 131
- Alcohol levels in blood can be determined by a redox reaction with potassium dichromate according to the balanced equation What is the blood alcohol level in mass percent if 8.76 mL of 0.049 88 M K2Cr2O7 is required for complete reaction with a 10.002 g sample of blood?
Problem 132
- Calcium levels in blood can be determined by adding oxa-late ion to precipitate calcium oxalate, CaC2O4, followed by dissolving the precipitate in aqueous acid and titrating the resulting oxalic acid (H2C2O4) with KMnO4: How many milligrams of Ca2+ are present in 10.0 mL of blood if 21.08 mL of 0.000 988 M KMnO4 solution is needed for the titration?
Problem 133
- Assume that you have 1.00 g of a mixture of benzoic acid (Mol. wt. = 122) and gallic acid (Mol. wt. = 170)), both of which contain one acidic hydrogen that reacts with NaOH. On titrating the mixture with 0.500 M NaOH, 14.7 mL of base is needed to completely react with both acids. What mass in grams of each acid is present in the original mixture?
Problem 134
Problem 135a
A compound with the formula XOCl2 reacts with water, yielding HCl and another acid H2XO3, which has two acidic hydrogens that react with NaOH. When 0.350 g of XOCl2 was added to 50.0 mL of water and the resultant solution was titrated, 96.1 mL of 0.1225 M NaOH was required to react with all the acid. (a) Write a balanced equation for the reaction of XOCl2 with H2O.
Problem 135b
A compound with the formula XOCl2 reacts with water, yielding HCl and another acid H2XO3, which has two acidic hydrogens that react with NaOH. When 0.350 g of XOCl2 was added to 50.0 mL of water and the resultant solution was titrated, 96.1 mL of 0.1225 M NaOH was required to react with all the acid. (b) What are the atomic mass and identity of element X?
- A procedure for determining the amount of iron in a sample is to convert the iron to Fe2+ and then titrate it with a solu-tion of Ce(NH4)2(NO3)6: What is the mass percent of iron in a sample if 1.2284 g of the sample requires 54.91 mL of 0.1018 M Ce(NH4)2(NO3)6 for complete reaction?
Problem 136
Problem 137a
Some metals occur naturally in their elemental state while others occur as compounds in ores. Gold, for instance, is found as the free metal; mercury is obtained by heating mercury(II) sulfide ore in oxygen; and zinc is obtained by heating zinc(II) oxide ore with coke (carbon). Judging from their positions in the activity series, which of the metals sil-ver, platinum, and chromium would probably be obtained by (a) finding it in its elemental state?
Problem 137c
Some metals occur naturally in their elemental state while others occur as compounds in ores. Gold, for instance, is found as the free metal; mercury is obtained by heating mercury(II) sulfide ore in oxygen; and zinc is obtained by heating zinc(II) oxide ore with coke (carbon). Judging from their positions in the activity series, which of the metals sil-ver, platinum, and chromium would probably be obtained by (c) heating its oxide with coke?
- A sample weighing 14.98 g and containing a small amount of copper was treated to give a solution containing aque-ous Cu2+ ions. Sodium iodide was then added to yield solid copper(I) iodide plus I3 with thiosulfate, S2O3 - ion, and the I3 - was titrated 2-. The titration required 10.49 mL of 0.100 M Na2S2O3 for complete reaction. What is the mass percent copper in the sample? The balanced equations are
Problem 138
Problem 139b
(b) If Ksp = 1.1 * 10-12 for Ag2CrO4, what are the molar concentrations of Ag+ and CrO4 2-in solution?
- A 100.0 mL solution containing aqueous HCl and HBr was titrated with 0.1235 M NaOH. The volume of base required to neutralize the acid was 47.14 mL. Aqueous AgNO3 was then added to precipitate the Cl-and Br-ions as AgCl and AgBr. The mass of the silver halides obtained was 0.9974 g. What are the molarities of the HCl and HBr in the original solution?
Problem 141
- A sample of metal (M) reacted with both steam and aqueous HCl to release H2 but did not react with water at room tem-perature. When 1.000 g of the metal was burned in oxygen, it formed 1.890 g of a metal oxide, M2O3. What is the iden-tity of the metal?
Problem 143
- An unknown metal (M) was found not to react with either water or steam, but its reactivity with aqueous acid was not investigated. When a 1.000 g sample of the metal was burned in oxygen and the resulting metal oxide converted to a metal sulfide, 1.504 g of sulfide was obtained. What is the identity of the metal?
Problem 144
- A mixture of acetic acid (CH3CO2H; monoprotic) and oxalic acid (H2C2O4; diprotic) requires 27.15 mL of 0.100 M NaOH to neutralize it. When an identical amount of the mixture is titrated, 15.05 mL of 0.0247 M KMnO4 is needed for complete reaction. What is the mass percent of each acid in the mixture? (Acetic acid does not react with MnO4 equation for the reaction of oxalic acid with MnO4 given in Problem 4.133.)
Problem 145
- Iron content in ores can be determined by a redox procedure in which the sample is first reduced with Sn2+, as in Problem 4.130, and then titrated with KMnO4 to oxidize the Fe2+ to Fe3+. The balanced equation is What is the mass percent Fe in a 2.368 g sample if 48.39 mL of a 0.1116 M KMnO4 solution is needed to titrate the Fe3 + ?
Problem 146
- A mixture of FeCl2 and NaCl is dissolved in water, and addi-tion of aqueous silver nitrate then yields 7.0149 g of a pre-cipitate. When an identical amount of the mixture is titrated with MnO4 -, 14.28 mL of 0.198 M KMnO4 is needed for complete reaction. What are the mass percents of the two compounds in the mixture? (Na+ and Cl-do not react with MnO4 -. The equation for the reaction of Fe2+ with MnO4 was given in Problem 4.146.)
Problem 147
- Salicylic acid, used in the manufacture of aspirin, contains only the elements C, H, and O and has only one acidic hydrogen that reacts with NaOH. When 1.00 g of salicylic acid undergoes complete combustion, 2.23 g CO2 and 0.39 g H2O are obtained. When 1.00 g of salicylic acid is titrated with 0.100 M NaOH, 72.4 mL of base is needed for complete reaction. What are the empirical and molecular formulas of salicylic acid?
Problem 148