📖 Theory▼

Aim: To determine the concentration of Fe²⁺ ions using acidified potassium permanganate (KMnO₄) titration.

Equation: MnO₄⁻ + 8H⁺ + 5Fe²⁺ → Mn²⁺ + 4H₂O + 5Fe³⁺

End point: First permanent pink/purple colour that persists for 30 seconds (KMnO₄ is self-indicating).

Note: The KMnO₄ (purple) decolourises as it reacts with Fe²⁺. When all Fe²⁺ is consumed, the next drop turns the solution pink permanently.

Setup

Burette: 0.02 mol/dm³ KMnO₄
Flask: 25.0 cm³ Fe²⁺ (unknown) + H₂SO₄

Controls

0.50 cm³

🔮 Predict before you titrate

Burette Reading

0.00 cm³
Add KMnO₄ until endpoint
⚠️ Safety
  • Potassium permanganate is a strong oxidiser and staining — keep away from combustible/organic material and avoid skin/clothing contact.
  • Acidify with dilute sulfuric acid (corrosive/irritant) — never HCl, whose chloride ions are also oxidised by MnO₄⁻ and give a falsely high titre.
  • Iron(II) salts are harmful if swallowed — no mouth-pipetting; use a pipette filler and wear goggles.
  • Read the burette at eye level from the top of the meniscus (KMnO₄ is too dark to read the bottom); handle glassware with care.
  • Rinse splashes immediately and collect waste in the labelled container.
KMnO₄ 0 25 50 Fe²⁺ + H₂SO₄ Conical Flask White tile ENDPOINT REACHED!
Observations
Add KMnO₄ to begin titration...