Which is a more powerful oxidizing agent: Potassium dichromate or Potassium permanganate?

Question

Is the oxidizing number most important factor here? Like the first one having an o. number of +6 and second one having an o. number of +7.
Are those compounds powerful oxidizing agents which have greater oxidizing number?

Sorry, I posted the wrong question. Can you tell me out of Manganese Dioxide and Potassium Manganate which is a more powerful oxidant?

Answer 1

Cleo is on the right track.
The most powerful oxidant will have the highest standard reduction potential.

You can find a very good table of such values at
http://www.northland.cc.mn.us/Chemistry/standard_reduction_potentials.htm

According to that, MnO4- has its strongest possible oxidative behaviour at mildly acidic pH with E0=+1.679 Volt for +7 -> +4 reduction. For the +7->+2 you have E0=+1.507 Volt

For MnO2 E0=+1.224 Volt
For K2Cr2O7 E0=+1.232 Volt

So the order is
MnO4- (+7->+4) >MnO4- (+7->+2) >> K2Cr2O7 ~ MnO2

Answer 2

I do not think oxidation number is a factor influencing oxidizing power. Oxidation power depends on the ion's ability to accept electrons (in the oxidizing agent).

Anyway, Potassium Permanganate is a more powerful oxidizing agent than potassium dichromate as Manganate (VII) has a higher standard electrode potential value (+1.52V) than Dichromate (VI) (at +1.33V), both in an acidic medium.

Answer 3

Mild Oxidizing Agent

Answer 4

The oxidising number is NOT the factor here.Its the amount of oxygen that is trapped withing the molecule.Let's take potassium permanganate for example.It's formula is KMnO4.Potassium dichromate has the formula K2CrO3.Therefore,if both are placed in a reducing agent to induce a redox reaction,like,say,an alkene,the KMnO4 will release more oxygen in solution simply because it has more oxygen trapped in it.Therefore,more oxygen = more oxidising power.

Answer 5

Your actual question: which is a more powerful oxidising agent: MnO2 (black solid) or KMnO4 (deep purple solid or solution)

Answer: KMnO4 potasium manganate (VII) is a powerful oxidising agent.

When both of these oxidising agents are reduced in a redox reaction, they both turn to Mn^2+ ions which are colourless. Yes, oxidation state o.s.(or oxidation number) has something to do with it.
The greater the o.s. (+7 of KMnO4) the more powerful its oxidising ability, compared to the o.s. of MnO2 where the o.s. is +4.

In fact if you pass a reducing gas, sulphur dioxide SO2, into a purple solution of potassium manganate (VII), it will turn first to solid MnO2 before the whole solution finally turns colourless as Mn^2+ is formed.

You may want to ask your Chemistry teacher to show you. I have done that before at my education centre in Singapore.

Answer 6

Take a look at this:
http://en.wikipedia.org/wiki/Oxidation_number
and this maybe:
Potassium dichromate is powerful:
http://en.wikipedia.org/wiki/Potassium_dichromate
Potassium permanganate:
http://en.wikipedia.org/wiki/Potassium_permanganate

Answer 7

I think Cr6+ is much stronger than Mn7+

Answer 8

permanganate