Substance Colour change observed 1 no change 2 brown to colourless 3 acidified manganate(VII): purple to colourless 4 no change The table lists the colour c...
Question 1 Report
| Substance | Colour change observed |
|---|---|
| 1 | no change |
| 2 | brown to colourless |
| 3 | acidified manganate(VII): purple to colourless |
| 4 | no change |
The table lists the colour change seen when each substance takes part in a reaction. Which substance is acting as an oxidising agent?
Answer Details
The named test in the table is the reliable one. Acidified potassium manganate(VII) is purple, and it fades to colourless only when it takes electrons from something else and is itself reduced to manganese(II). Taking electrons is what an oxidising agent does, so substance 3, the one showing purple to colourless, is acting as the oxidising agent.
Substances that show no change have not taken part in any electron transfer, so neither of those rows can be an agent of any kind. The brown to colourless row does not name its reagent, so no safe redox conclusion can be drawn from it; only the labelled manganate(VII) result is decisive.
Learn the two key colour tests: manganate(VII) fading, and colourless iodide turning brown.
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