Worksheet: Reduction–Oxidation Titrations

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


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.


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?

  • A48%
  • B24%
  • C14%
  • D28%
  • E40%


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?

  • A18%
  • B36%
  • C1.6%
  • D53%
  • E47%


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.


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.


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


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


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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