NSSCAS Chemistry · 8224/3 · Redox titration

Alloy redox titration

A 2.00 g sample of iron alloy has been dissolved in dilute sulfuric acid and made up to 250 cm³. A 25.0 cm³ aliquot is titrated against 0.0200 M potassium manganate(VII). The first permanent pink colour marks the end-point, from which the percentage of iron in the alloy can be calculated.

burette: 0.00 cm³

m alloy

2.00 g

[KMnO₄]

0.0200 M

endpoint

—

Calculation

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

Exam-style questions

1. Why is KMnO₄ called a SELF-INDICATOR?

2. Balanced ionic equation:

3. Why is dilute H₂SO₄ (not HCl) used to acidify the Fe²⁺ solution?

4. 28.80 cm³ of 0.0200 M KMnO₄ for 25.0 cm³ aliquot (250 cm³ stock from 2.00 g alloy). Calculate %Fe.