Answered: Give the oxidation number of an atom in…

Give the oxidation number of an atom in the compound a. Mn in Mn04- b. Cr in CrO2 2+ c. Fe in Fe304 d. K in KCIO3 e. B in Na2B407

Chemistry: The Molecular Science

5th Edition

ISBN:9781285199047

Author:John W. Moore, Conrad L. Stanitski

Publisher:John W. Moore, Conrad L. Stanitski

Chapter3: Chemical Reactions

Section: Chapter Questions

Problem 49QRT

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The blood alcohol (C2H5OH) level can be determined by titrating a sample of blood plasma with an acidic potassium di-chromate solution, resulting in the production of Cr3+ (aq) and carbon dioxide. The reaction can be monitored because the dichromate ion (Cr2O72) is orange in solution, and the Cr3+ ion is green. The balanced equations is 16H+(aq) + 2Cr2O72(aq) + C2H5OH(aq) 4Cr4+(aq) + 2CO2(g) + 11H2O(l) This reaction is an oxidationreduction reaction. What species is reduced, and what species is oxidized? How many electrons are transferred in the balanced equation above?
You have two 500.0-mL aqueous solutions. Solution A is a solution of a metal nitrate that is 8.246% nitrogen by mass. The ionic compound in solution B consists of potassium, chromium, and oxygen; chromium has an oxidation state of + 6 and there are 2 potassiums and 1 chromium in the formula. The masses of the solutes in each of the solutions are the same. When the solutions are added together, a blood-red precipitate forms. After the reaction bas gone to completion, you dry the solid and find that it has a mass of 331.8 g. a. Identify the ionic compounds in solution A and solution B. b. Identify the blood-red precipitate. c. Calculate the concentration (molarity) of all ions in the original solutions. d. Calculate the concentration (molarity) of all ions in the final solution.
Determine the oxidation states of the elements in the following compounds: (a) Nal (b) GdCl3 (c) LiNO3 (d) H2Se (e) Mg2Si (f) RbO2, rubidium superoxide (g) HF
A transition metal X forms an oxide of formula X2O3. It is found that only 50% of X atoms in this compound are in the +3 oxidation state. The only other stable oxidation states of X are +2 and +5. What percentage of X atoms are in the +2 oxidation state in this compound?
4.112 A metallurgical firm wishes to dispose of 1300 gallons of waste sulfuric acid whose molarity is 1.37 M. Before disposal, it will be reacted with calcium hydroxide (slaked lime), which costs $0.23 per pound. (a) Write the balanced chemical equation for this process. (b) Determine the cost that the firm will incur from this use of slaked lime.
Gold can be dissolved from gold-bearing rock by treating the rock with sodium cyanide in the presence of oxygen. 4 Au(s) + 8 NaCN(aq) + O2(g) + 2 H2O() 4 NaAu(CN)2(aq) + 4 NaOH(aq) (a) Name the oxidizing and reducing agents in this reaction. What has been oxidized, and what has been reduced? (b) If you have exactly one metric ton (1 metric ton = 1000 kg) of gold-bearing rock, what volume of 0.075 M NaCN, in liters, do you need to extract the gold if the rock is 0.019% gold?
To analyze an iron-containing compound, you convert all the iron to Fe2+ in aqueous solution and then titrate the solution with standardized KMnO4. The balanced, net ionic equation is MnO4(aq) + 5 Fe2(aq) + 8 H3O+(aq) Mn2(aq) + 5 Fe3+(aq) + 12 H2O(l) A 0.598-g sample of the iron-containing compound requires 22.25 mL of 0.0123 M KMnO4 for titration to the equivalence point. What is the mass percent of iron in the sample?
Chromium has been investigated as a coating for steel cans. The thickness of the chromium film is determined by dissolving a sample of a can in acid and oxidizing the resulting Cr3+ to Cr2O72 with the peroxydisulfate ion: S2O82(aq) + Cr3+(aq) + H2O(l) Cr2O72(aq) + SO42(aq) + H+(aq) (Unbalanced) After removal of unreacted S2O82 an excess of ferrous ammonium sulfate [Fe(NH4)2(SO4)26H2O] is added, reacting with Cr2O72 produced from the first reaction. The unreacted Fe2+ from the excess ferrous ammonium sulfate is titrated with a separate K2Cr2O7 solution. The reaction is: H+(aq) + Fe2+(aq) + Cr2O72(aq) Fe3+(aq) + Cr3+(aq) + H2O(l) (Unbalanced) a. Write balanced chemical equations for the two reactions. b. In one analysis, a 40.0-cm2 sample of a chromium-plated can was treated according to this procedure. After dissolution and removal of excess S2O82, 3.000 g of Fe(NH4)2(SO4)26H2O was added. It took 8.58 mL of 0.0520 M K2Cr2O7 solution to completely react with the excess Fe2+. Calculate the thickness of the chromium film on the can. (The density of chromium is 7.19 g/cm3)
The iron content of hemoglobin is determined by destroying the hemoglobin molecule and producing small water-soluble ions and molecules. The iron in the aqueous solution is reduced to iron(II) ion and then titrated against potassium permanganate. In the titration, iron(ll) is oxidized to iron(III) and permanganate is reduced to manganese(II) ion. A 5.00-g sample of hemoglobin requires 32.3 mL of a 0.002100 M solution of potassium permanganate. The reaction with permanganate ion is MnO4(aq)+8H+(aq)+5Fe2+(aq)Mn2+(aq)+5Fe3+(aq)+4H2O What is the mass percent of iron in hemoglobin?
Triiodide ions are generated in solution by the following (unbalanced) reaction in acidic solution: IO3(aq) + I(aq) I3(aq) Triiodide ion concentration is determined by titration with a sodium thiosulfate (Na2S2O3) solution. The products are iodide ion and tetrathionate ion (S4O6). a. Balance the equation for the reaction of IO3 with I ions. b. A sample of 0.6013 g of potassium iodate was dissolved in water. Hydrochloric acid and solid potassium iodide were then added. What is the minimum mass of solid KI and the minimum volume of 3.00 M HQ required to convert all of the IO3 ions to I ions? c. Write and balance the equation for the reaction of S2O32 with I3 in acidic solution. d. A 25.00-mL sample of a 0.0100 M solution of KIO. is reacted with an excess of KI. It requires 32.04 mL of Na2S2O3 solution to titrate the I3 ions present. What is the molarity of the Na2S2O3 solution? e. How would you prepare 500.0 mL of the KIO3 solution in part d using solid KIO3?
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, it took 31.92 mL of 0.289 M HCl to titrate the excess NaOH. Calculate the purity of the aspirin. What indicator should be used for this titration? Why?
The amount of oxygen, O2, dissolved in a water sample at 25 C can be determined by titration. The first step is to add solutions of MnSO4 and NaOH to the water to convert the dissolved oxygen to MnO2. A solution of H2SO4 and KI is then added to convert the MnO2 to Mn2+, and the iodide ion is converted to I2. The I2 is then titrated with standardized Na2S2O3. (a) Balance the equation for the reaction of Mn2+ ions with O2 in basic solution. (b) Balance the equation for the reaction of MnO2 with I in acid solution. (c) Balance the equation for the reaction of S2O32 with I2. (d) Calculate the amount of O2 in 25.0 mL of water if the titration requires 2.45 mL of 0.0112 M Na2S2O3 solution.