The table below shows the common and important oxidizing agents:
| Oxidizing Agent | Half Equation | Colour change when added to reducing agent | Application |
|---|---|---|---|
| Acidified potassium manganate (VII)
$\text{KMnO}_{4}$ | $\text{MnO}_{4}^{-} (\text{aq}) + 8 \text{H}^{+} (aq) + 5\text{e}^{-} \rightarrow \text{Mn}^{2+} (\text{aq}) + 4 \text{H}_{2}\text{O}(\text{l})$ | Purple to pale pink (or colourless) | Used to test for reducing agent |
| Acidified potassium dichromate(VI)
$\text{K}_{2}\text{Cr}_{2}\text{O}_{7}$ | $\text{Cr}_{2}\text{O}_{7}^{2-} (\text{aq}) + 14\text{H}^{+}(\text{aq}) + 6 \text{e}^{-} \rightarrow 2\text{Cr}^{3+} + 7\text{H}_{2}\text{O}$ | Orange to green | Oxidizes alcohol to acids; used to test for $\text{SO}_{2}$ gas |
| Chlorine
$\text{Cl}_{2}$ | $\text{Cl}_{2} (\text{g}) + 2\text{e}^{-} \rightarrow 2\text{Cl}^{-} (\text{g})$ | Greenish yellow to colourless | Oxidizes bromide to bromine and iodide to iodine |
Testing for presence of reducing agent:
- Add an oxidising agent, e.g. Aqueous potassium manganate (VII) to the reducing agent
- Shake the mixture
- The aqueous potassium manganate (VII) is decolourised
The table below shows the common and important reducing agents.
| Reducing Agent | Half Equation | Colour change when added to oxidizing agent | Application |
|---|---|---|---|
| Aqueous potassium iodide
$\text{KI}$ | $2\text{I}^{-} (\text{aq}) \rightarrow \text{I}_{2} (\text{aq}) + 2\text{e}^{-}$ | Colourless to brown | Used to test for oxidizing agent |
| Aqueous iron(III) sulphate
$\text{FeSO}_{4}$ | $\text{Fe}^{2+} (\text{aq}) \rightarrow \text{Fe}^{3+} (\text{aq}) + \text{e}^{-}$ | Green to brown | – |
| Carbon Monoxide
$\text{CO}$ | – | – | Used to reduce iron oxides to iron in blast furnace |
| Hydrogen | $\text{H}_{2} (\text{g}) \rightarrow 2\text{H}^{+} (\text{aq}) + 2\text{e}^{-}$ | – | Reduces copper(II) oxide to copper |
| Metals
E.g. $\text{Mg}$, $\text{Na}$ | – | – | Displacement of less reactive metals |
Testing for presence of oxidising agent:
- Add a reducing agent, e.g. Aqueous potassium iodide to the oxidising agent.
- Shake the mixture.
- A brown solution of iodine is produced.
- The presence of iodine can be confirmed by adding starch solution.
- A dark blue coloration is obtained.
thank you
Why don’t you tell us the SIMPLE way of testing each agent, i.e, without any examples?
Rajdeep is right.It would be more easier for us to understand it
You guys should also use ammonium sulphate and pottasium dicromate