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2. | |
| Drip feeding of hydrogen bromide solution; reaction begins | Increasing bromine vapor |
| Photo 1: | Experimental setup: A 48 percent hydrogen bromide solution is drip fed to 5 g potassium permanganate. |
| Photo 2: | The bromine vapor produced is clearly noticeable. Potassium permanganate reacts with hydrogen bromide according to:
2 MnO4- + 16 H+ + 10 Br- > 5 Br2 + 2 Mn2+ + 8 H2O
Potassium permanganate is a relatively strong oxidating material. The standard potential of the system [Mn2+ + 4 H2O / MnO4- + 8 H+] in an acidic solution
has a value of 1.51 V; the value for the system [2 Br- / Br2] in an acid solution amounts to only 1.065 V.
If the experiment is performed with hydrochloric acid and potassium permanganate, the analog produced is elemental chlorine (standard potential [2 Cl- / Cl2] in acidic solution: 1.36 V).
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