acidified KMnO4

acidify 即係提供酸性環境令MnO4-作為oxidizing agent的反應可以發生：

MnO4- + 8H+ + 5e- => Mn2+ + 4H2O
(明顯這個反應需要H+才可以發生)

KMnO4 可以用 dilute H2SO4 去 acidify，因為兩者並無reaction，即係H2SO4真正只提供acidic medium


如果用HCl，會與MnO4- react，咁就會消耗左MnO4-，唔係acidify
MnO4- + 10Cl- + 16H+ => Mn2+ + 5Cl2 + 8H2O


如果用HNO3，因本身HNO3都是oxidizing agent，當MnO4- 進行redox reaction時，HNO3也會參與redox reaction，使反應出現副反應，干擾了實驗。

To Leo :

What is the reaction between conc. sulphuric acid and KMnO4 (aq)? (No reaction)

What is the reaction between conc. nitric acid and KMnO4? (No reaction)

Is the oxidation of HCl(aq) due to its low stability? (No, it is due to the strong oxidizing power of KMnO4. HCl is stable.)

2014-01-20 09:10:38 補充：
To Leo :

If you know nothing, you have to learn and ask, but not to answer.

When concentrated H2SO4 is mixed with KMnO4, the reaction is too vigorous.

When either conc and dil HNO3 is mixed with KMnO4, the reaction is also too vigorous.

But it is safe to adjust the acidity of KMnO4 by dilute H2SO4 and the sulphate ioncould not be oxidized under the experimental condition.

2014-01-19 23:53:28 補充：
chloride of HCl is unstable that it is oxidized to chlorine.

2014-01-20 11:25:30 補充：
I would like to bring out the likelihood and hazard of the chemical experiment, otherwise people would really try in the laboratory.

Never try mixing conc H2SO4 or conc HNO3 with KMnO4. Please read one of the reference materials cited below. It is serious.



.

2014-01-20 11:28:08 補充：
4KMnO4+ 12HNO3--> 4KNO3 + 4Mn(NO3)2 +6H2O +5O2

...reaction between KMnO4 and 65% HNO3...



It does happen with 96% H2SO4, but not anymore with 60% H2SO4 .

2014-01-20 11:29:34 補充：
Addition of some permanganate to red fuming nitric acid ... This indeed forms a strong oxidizing mixture, ...added a drop of turpentine to some of the same fuming acid containing some KMnO4 and a flame shot out.

2014-01-20 11:30:23 補充：
Regarding, the oxidation of Chloride ion to chlorine, it is due to its thermodynamic stability when mixed with KMnO4, in terms of reduction/oxidation potential. At advanced research level, we do not merely say strong/weak oxidizing/reducing power, we use overall chemical potentials instead.

2014-01-20 11:33:48 補充：
This is the valid website for the reference material.

KMnO₄ 是一個氧化劑，HNO₃ 也是一個 氧化劑。

如果把 KMnO₄ 和 HNO₃ 一同加到 Fe²⁺ 中，到底是 KMnO₄ 還是 HNO₃ 把 Fe²⁺ 氧化了呢 ？ 還是 x% 由 KMnO₄ 達成，y% 由 HNO₃ 達成呢？唔好玩啦！

另外 KMnO₄ 是一個氧化劑，會把 Cl⁻ 氧化為 Cl₂。