Redox Titration with Potassium Permanganate

Determining iron(II) concentration using KMnO₄

Titrations Advanced (University) 50 min ~$18.00

Objective

Determine the concentration of an iron(II) sulfate solution by titrating with standardized potassium permanganate, a self-indicating reagent.

Background

Potassium permanganate is a powerful oxidizing agent that reacts with Fe2+ in acidic solution. MnO4- (purple) is reduced to Mn2+ (nearly colorless), so permanganate acts as its own indicator. The endpoint occurs when a single drop of excess KMnO4 produces a permanent pink/purple color.

Safety Warnings

  • KMnO₄ stains skin and clothing permanently
  • H₂SO₄ is corrosive
  • Wear safety goggles and gloves throughout
  • Wipe up KMnO₄ spills immediately

Required PPE

goggles gloves lab_coat

Materials

  • Iron(II) sulfate solution (100 mL)
    Unknown concentration
  • Potassium permanganate (KMnO₄) (100 mL)
    0.02M standardized
  • Sulfuric acid (H₂SO₄) (50 mL)
    1M
  • Distilled water (200 mL)

Equipment

50 mL burette Burette stand and clamp 250 mL Erlenmeyer flask 25 mL pipette Pipette filler White tile

Procedure

1

Rinse the burette with KMnO₄ solution, then fill to the 0 mL mark. Record the meniscus reading (read from the top of the meniscus since KMnO₄ is opaque).

5 min KMnO₄ stains — handle carefully
2

Pipette exactly 25.0 mL of iron(II) sulfate solution into the Erlenmeyer flask.

3 min
3

Add 10 mL of 1M sulfuric acid to the flask to ensure acidic conditions.

2 min Handle acid carefully
4

Slowly add KMnO₄ from the burette while swirling. Each drop will decolorize as Fe2+ reduces MnO4-.

10 min
5

As the endpoint approaches, add drop by drop until a faint permanent pink/purple color persists for 30 seconds.

5 min
6

Record the final burette reading and calculate the volume used.

2 min
7

Repeat at least twice for concordant results.

15 min
8

Calculate the Fe2+ concentration using the balanced equation: MnO4- + 5Fe2+ + 8H+ → Mn2+ + 5Fe3+ + 4H2O.

5 min

Expected Results

The solution should transition from colorless to a persistent faint pink/purple at the endpoint. The 1:5 molar ratio of KMnO₄ to Fe2+ should yield an accurate concentration.

Cleanup

Dilute waste solutions and dispose of KMnO₄ waste according to lab protocols. Rinse the burette thoroughly with water. Clean any stains with dilute acid or sodium sulfite.

Details

Category
Titrations
Difficulty
Advanced (University)
Duration
50 min
Est. Cost
$18.00
Steps
8
Materials
4

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Frequently Asked Questions

What is the objective of Redox Titration with Potassium Permanganate?
Determine the concentration of an iron(II) sulfate solution by titrating with standardized potassium permanganate, a self-indicating reagent.
How difficult is Redox Titration with Potassium Permanganate?
This experiment is rated as Advanced (University). It takes approximately 50 minutes to complete.
What safety precautions are needed for Redox Titration with Potassium Permanganate?
Key safety precautions include: KMnO₄ stains skin and clothing permanently; H₂SO₄ is corrosive; Wear safety goggles and gloves throughout.
What materials are needed for Redox Titration with Potassium Permanganate?
The main materials required are: Iron(II) sulfate solution, Potassium permanganate (KMnO₄), Sulfuric acid (H₂SO₄), Distilled water.
What results should I expect from Redox Titration with Potassium Permanganate?
The solution should transition from colorless to a persistent faint pink/purple at the endpoint. The 1:5 molar ratio of KMnO₄ to Fe2+ should yield an accurate concentration.