---
title: "Initial rate: iodine clock Template – Chemistry Diagram | MolDraw"
url: https://www.moldraw.com/templates/setup-iodine-clock/
description: "Initial rate: iodine clock template: Stopwatch, starch, hydrogen peroxide in a measuring cylinder and a beaker of iodide, acid and thiosulfate on a white…"
lang: en
publisher: Scidart Academy
generated: 2026-10-28
---
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# Initial rate: iodine clock template

![Initial rate: iodine clock template: Stopwatch, starch, hydrogen peroxide in a measuring cylinder and a beaker of iodide, acid and thiosulfate on a white tile. A-level / AP / IB.](https://www.moldraw.com/templates/setup-iodine-clock.webp)

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Stopwatch, starch, hydrogen peroxide in a measuring cylinder and a beaker of iodide, acid and thiosulfate on a white tile. A-level / AP / IB.

## What the template shows

- Time how long a fixed amount of iodine takes to form; rate ∝ 1/t
- H₂O₂(aq), added last
- Pour it all in at once and start the clock
- Blue-black once all the thiosulfate is used up and free I₂ remains
- Stop at the first blue-black colour; repeat with other concentrations
- Reaction mixture
- KI, dilute H₂SO₄, a small fixed amount of Na₂S₂O₃, starch and water to the same total volume each run
- H₂O₂ + 2H⁺ + 2I⁻ → I₂ + 2H₂O, then I₂ + 2S₂O₃²⁻ → 2I⁻ + S₄O₆²⁻. Persulfate version: S₂O₈²⁻ + 2I⁻ → 2SO₄²⁻ + I₂
- White tile
- Swirl once to mix; judge the colour change against the tile the same way each run
- Reaction setup

Drawn with 13 shapes – every one editable in MolDraw.

## Sources

- [Atkins, de Paula & Keeler, Atkins' Physical Chemistry, 11th ed., OUP 2018](https://openlibrary.org/isbn/9780198769866) Textbook

## How to use this template

1. Press **Edit in MolDraw**. The template opens on the canvas of the free MolDraw editor.
2. Change anything: move structures, edit atoms and labels, recolour highlights or delete what you do not need.
3. Add your own structures, arrows and text next to it, or combine several templates on one page.
4. Export the drawing as PNG, SVG or PDF for slides, worksheets, theses and papers.

## Frequently asked questions

### Is the Initial rate: iodine clock template free?

You can preview the Initial rate: iodine clock template here and open and edit it in MolDraw for free. Downloading or exporting it is part of MolDraw Pro, together with the other premium templates.

### Can I edit the Initial rate: iodine clock template?

Yes. It opens as an ordinary MolDraw drawing, so every structure, arrow, label and colour can be changed, and you can add your own content around it.

### Is the chemistry checked?

Every structure is checked with RDKit and every curly arrow passes MolDraw’s electron-flow audit. The sources used are listed on this page.

### Can I edit the glassware?

Yes. Every piece of glassware is a MolDraw apparatus object: move, resize, recolour the liquid or swap a piece and the joints stay connected.

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