---
title: "Redox Titrations with Manganate(VII) and Thiosulfate"
description: "A redox titration needs no separate indicator when one reagent changes colour as it reacts. Manganate(VII) against iron(II), and iodine against thiosulfate, are the two routines worth owning."
canonical: https://lightmysky.com/learn/science/redox-titrations-with-manganate-vii-and-thiosulfate-mt_tKZTSfo0Ra
source: https://lightmysky.com/learn/science/redox-titrations-with-manganate-vii-and-thiosulfate-mt_tKZTSfo0Ra.md
retrieved: 2026-09-12
---

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# Redox Titrations with Manganate(VII) and Thiosulfate

A redox titration needs no separate indicator when one reagent changes colour as it reacts. Manganate(VII) against iron(II), and iodine against thiosulfate, are the two routines worth owning.

Subject: Science · Area: Chemistry · Ages 17 to 18
Page: https://lightmysky.com/learn/science/redox-titrations-with-manganate-vii-and-thiosulfate-mt_tKZTSfo0Ra

## Ready when they can

- Explains why manganate(VII) acts as its own indicator and describes the end point
- Builds the full ionic equation from the two half equations before calculating anything
- Calculates the concentration or the purity of a sample from the titre and the mole ratio
- Explains why the iodine and thiosulfate route needs starch added only near the end

## Lesson: Redox titrations that show their own end

Manganate(VII) is its own indicator in acid solution, so you add no separate indicator at all. The end point is the first faint pink that stays, which is the first drop of extra manganate tinting the flask.

Before any numbers, build the full ionic equation from the two half equations. Manganate takes 5 electrons while each iron(II) gives 1, so 1 manganate reacts with 5 iron(II).

**Example.** Picture a dissolved iron tablet needing 25.0 cm3 of 0.020 M manganate. That is 5.0 x 10-4 mol of manganate, times 5 gives 2.5 x 10-3 mol of iron, times 55.8 gives 0.1395 g of iron in the tablet.

**Tip.** With iodine and thiosulfate, hold the starch back until near the end. Added early, starch locks onto the iodine and will not let go cleanly, so the finish drags and the end point blurs.

**Recap.** Manganate shows its own pink end, half equations fix the 1 to 5 ratio, titres give mass, and starch waits until near the end.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Oxidation Numbers and Balancing Redox Equations](https://lightmysky.com/learn/science/oxidation-numbers-and-balancing-redox-equations-mt_4xuYKYgUex)
- [Titration: Finding an Unknown Concentration](https://lightmysky.com/learn/science/titration-finding-an-unknown-concentration-mt_7WLN35XxYx)
- [Standard Electrode Potentials and Predicting Redox Reactions](https://lightmysky.com/learn/science/standard-electrode-potentials-and-predicting-redox-reactions-mt_LDI10CjoAI)

## Opens up

- [Transition Metals: Variable Oxidation State, Colour and Catalysis](https://lightmysky.com/learn/science/transition-metals-variable-oxidation-state-colour-and-catalysis-mt_UIVC6d7wak)
- [Calibration, the Blank and What Makes a Measurement Trustworthy](https://lightmysky.com/learn/science/calibration-the-blank-and-what-makes-a-measurement-trustworthy-mt_UNkQFonlWJ)