Core practical 11 - Redox Titrations

Question 1

Iron and Potassium manganate redox equation

Answer 1

MnO4-(aq) + 8H+(aq) + 5Fe2+ (aq) -> Mn2+ (aq) + 4H2O (l) + 5Fe3+ (aq)

Question 2

Steps for redox titration

Answer 2

1. Crush iron tablets using mortar and pestle and measure the mass
2. Dissolve the known mass of iron tablets with 1.5M sulfuric acid in a beaker
3. Pour the contents of the beaker into a volumetric flask and make up to 250cm^3 (the line)
4. Pipette 25cm^3 into a clean beaker
5. Fill a burette with 0.005M of KMnO4 (potassium manganate)
6. Titrate until you see a pale pink colour appear
7. Repeat until 2 concordant results are observed

Question 3

Why do we need no indicator

Answer 3

• The MnO4- acts as the indicator as it has a colour (purple)