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Lesson: Reduction–Oxidation Titrations

In this lesson, we will learn how to describe iodometry, iodimetry, and other redox titration methods and troubleshoot common errors.

Worksheet • 8 Questions

Q1:

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

  • ALowering the pH of an acidic analyte solution.
  • BUsing only fresh thiosulfate solutions.
  • CUsing excess iodide in the iodine solution.
  • DUsing only fresh iodide solutions.
  • EAdding starch indicator to the iodine solution.

Q2:

A 0.357 g sample contains only lead(II) iodide and sodium iodide in 100 mL of distilled water. Titration to the Fajan’s end point 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 5 3 %
  • B 4 7 %
  • C 1 8 %
  • D 1 . 6 %
  • E 3 6 %

Q3:

Which of the following is an accurate description of iodometry?

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

Q4:

Oxalic acid ( H C O ) 2 2 4 and potassium permanganate ( K M n O ) 4 react according to the net ionic equation:

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.

Q5:

A 58.3 mg sample containing S n 2 + is dissolved in 1.0 M   H C l . If 23.6 mL of 0.010 M  T l 3 + 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 1 4 %
  • C 2 8 %
  • D 4 0 %
  • E 2 4 %

Q6:

Adding aqueous sodium chloride to aqueous silver ( I ) nitrate results in the precipitation of silver ( I ) chloride: 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.

  • A 0.283 M
  • B 0.270 M
  • C 0.145 M
  • D 0.128 M
  • E 0.203 M

Q7:

Copper(II) nitrate reacts with potassium iodide in water to produce solid copper(I) iodide and elemental iodine:

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.

  • A 161.4 mL
  • B 180.0 mL
  • C 153.0 mL
  • D 175.1 mL
  • E 179.4 mL

Q8:

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 highly colored than iodine in water.
  • DTriiodide ions are more stable than iodine when stored under air.
  • ETriiodide ions are more strongly oxidizing than iodine.
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