Worksheet: Reduction–Oxidation Titrations

In this worksheet, we will practice describing iodometry, iodimetry, and other redox titration methods and troubleshooting common errors.

Q1:

Oxalic acid (HCO)224 and potassium permanganate (KMnO)4 react according to the shown net ionic equation. 2MnO()+5HCO()+6H()10CO()+2Mn()+8HO()4224+22+2aqaqaqgaql

Titration of a 20.0 mL aqueous solution of oxalic acid required 23.24 mL of 0.09113 M aqueous potassium permanganate. Calculate, to 3 significant figures, the concentration of the oxalic acid solution.

Q2:

A 58.3 mg sample containing Sn2+ is dissolved in 1.0 MHCl. If 23.6 mL of 0.010 MTl3+ is required to reach the end point of the titration, what is the mass percent (w/w%) of tin in the original sample?

  • A 4 8 %
  • B 2 4 %
  • C 1 4 %
  • D 2 8 %
  • E 4 0 %

Q3:

A 0.357 g sample contains only lead(II) iodide and sodium iodide in 100 mL of distilled water. Titration to Fajans’s endpoint requires 22.37 mL of 0.050 M silver nitrate. What is the mass percent (w/w%) of lead(II) iodide in the sample?

  • A 1 8 %
  • B 3 6 %
  • C 1 . 6 %
  • D 5 3 %
  • E 4 7 %

Q4:

Triiodide ions are produced by the reaction of iodine with iodide ions. Why should iodine solutions contain an additional iodide salt if used as a titrant?

  • ATriiodide salts are more soluble in water than iodine.
  • BTriiodide ions undergo a more visible color change during reduction–oxidation reactions.
  • CTriiodide ions are more strongly oxidizing than iodine.
  • DTriiodide ions are more highly colored than iodine in water.
  • ETriiodide ions are more stable than iodine when stored under air.

Q5:

Which of the following is an accurate description of iodometry?

  • AExcess analyte is reacted with iodine, and the remainder is titrated against sodium thiosulfate.
  • BIodine is used as a titrant for an oxidizing analyte.
  • CIodine is used as a titrant for a reducing analyte.
  • DExcess sodium thiosulfate is reacted with an analyte, and the remainder is titrated against iodine.
  • EExcess iodide is reacted with an analyte, and the resulting iodine is titrated against sodium thiosulfate.

Q6:

Which of the following would not improve the accuracy of an iodometric titration?

  • AUsing only fresh thiosulfate solutions
  • BUsing excess iodide in the iodine solution
  • CUsing only fresh iodide solutions
  • DAdding starch indicator to the iodine solution
  • ELowering the pH of an acidic analyte solution

Q7:

Copper(II) nitrate reacts with potassium iodide in water to produce solid copper(I) iodide and elemental iodine, as shown. 2Cu(NO)()+4KI()2CuI()+I()+4KNO()3223aqaqsaqaq

A copper(II) nitrate solution has a volume of 43.88 mL and concentration of 0.3842 M. Calculate the volume of a 0.2089 M potassium iodide solution needed to convert all of the copper(II) nitrate to copper(I) iodide.

  • A161.4 mL
  • B180.0 mL
  • C153.0 mL
  • D179.4 mL
  • E175.1 mL

Q8:

Adding aqueous sodium chloride to aqueous silver(I) nitrate results in the precipitation of silver(I) chloride, as shown. AgNO()+NaCl()AgCl()+NaNO()33aqaqsaq Calculate the concentration of silver(I) nitrate in a 23.00 mL aqueous sample if 32.10 mL of 0.203 M aqueous sodium chloride is required for the end point to be reached.

  • A0.283 M
  • B0.270 M
  • C0.145 M
  • D0.128 M
  • E0.203 M

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