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Author: Subject: Dissolving Manganese Dioxide in Sulfuric Acid?
nikotyna1939
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[*] posted on 14-3-2024 at 00:44
Dissolving Manganese Dioxide in Sulfuric Acid?


At what temprerature will Manganese Dioxide starting to dissolve in Sulfuric Acid to produce Manganese Sulfate?
Does Manganese Dioxide reacts with Sulfuric Acid at room temprerature?
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RU_KLO
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[*] posted on 14-3-2024 at 03:53


I think not, because MnO2 is insoluble.
But boiling concentrated H2SO4 (VERY VERY DANGEROUS) could dissolve MnSO4.

like I said in another of your posts, the route is to transform MnO2 to Mn2O3 by blowtorch heat and then leach it with H2SO4. ( I use 30% conc. ie battery acid concentration)

Check the permanganate post.




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Sulaiman
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[*] posted on 14-3-2024 at 05:43


In Wikipedia, manganese dioxide, reactions

Hot concentrated sulfuric acid reduces MnO2 to manganese(II) sulfate:

2 MnO2 + 2 H2SO4 → 2 MnSO4 + O2 + 2 H2O
......................................
So the evolution of oxygen should drive the reaction,

and, at a guess, if hot enough (boiling) the water would also be boiled off, increasing yield that may otherwise be decreased by atmospheric oxygen?
(as above - boiling conc. sulphuric acid is hazardous - it can 'bump' VIOLENTLY, so take extra care)

PS when the solution cools I would expect anhydrous manganese sulphate to precipitate out,
probably VERY hygroscopic.
Another guess ;)

[Edited on 14-3-2024 by Sulaiman]




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[*] posted on 14-3-2024 at 06:13


Add a reducing agent such as hydrogen peroxide (in dilute, not concentrated acid) if you want the reaction to go at reasonable temperatures.



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chornedsnorkack
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[*] posted on 15-3-2024 at 05:23


Remember that "concentrated sulphuric acid" actually spans a vast range of Hammett acidity values.
Quoting some numbers from a table by Ryabova et al. 1966:


  • 3% +0,31
  • 5% -0,02
  • 18% -0,97
  • 20% -1,10
  • 30% -1,82
  • 32% -1,96
  • 35% -2,19
  • 45% -2,95
  • 47% -3,13
  • 55% -3,91
  • 57% -4,15
  • 62% -4,82
  • 65% -5,18
  • 70% -5,92
  • 72% -6,23
  • 75% -6,72
  • 77% -7,05
  • 82% -7,84
  • 85% -8,29
  • 87% -8,60
  • 90% -9,03
  • 96% -9,88
  • 98% -10,27
  • 99% -10,57
  • 99,6% -10,92
  • 99,7% -11,01
  • 99,95% -11,64
  • 100.00% -11,94

So, not only the behaviour of 30% and 96% acid are different, but both are quite different from what happens at 70% or 100,00%.


[Edited on 15-3-2024 by chornedsnorkack]
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Sulaiman
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[*] posted on 15-3-2024 at 05:56


In a textbook/lab/home/classroom context
unless otherwise specified
"concentrated sulphuric acid"
means near azeotropic.
Anything else would need a concentration specification.
(molarity, w/w%, 'chamber' etc.)

[Edited on 15-3-2024 by Sulaiman]




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[*] posted on 15-3-2024 at 07:14


Am sorry to drift this off topic a little, but why the dioxide not react with sulfuric acid to make Mn(SO4)2?, i expect oxidizer to react with acid usually.

[Edited on 15-3-2024 by fx-991ex]
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[*] posted on 15-3-2024 at 08:29


Quote: Originally posted by chornedsnorkack  
Remember that "concentrated sulphuric acid" actually spans a vast range of Hammett acidity values.
Quoting some numbers from a table by Ryabova et al. 1966:


  • 3% +0,31
  • 5% -0,02
  • 18% -0,97
  • 20% -1,10
  • 30% -1,82
  • 32% -1,96
  • 35% -2,19
  • 45% -2,95
  • 47% -3,13
  • 55% -3,91
  • 57% -4,15
  • 62% -4,82
  • 65% -5,18
  • 70% -5,92
  • 72% -6,23
  • 75% -6,72
  • 77% -7,05
  • 82% -7,84
  • 85% -8,29
  • 87% -8,60
  • 90% -9,03
  • 96% -9,88
  • 98% -10,27
  • 99% -10,57
  • 99,6% -10,92
  • 99,7% -11,01
  • 99,95% -11,64
  • 100.00% -11,94

So, not only the behaviour of 30% and 96% acid are different, but both are quite different from what happens at 70% or 100,00%.


[Edited on 15-3-2024 by chornedsnorkack]



...is that the density of each concentration of the acid?




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[*] posted on 15-3-2024 at 09:28


Quote: Originally posted by solo  
Quote: Originally posted by chornedsnorkack  
Remember that "concentrated sulphuric acid" actually spans a vast range of Hammett acidity values.
Quoting some numbers from a table by Ryabova et al. 1966:


  • 3% +0,31
  • 5% -0,02
  • 18% -0,97
  • 20% -1,10
  • 30% -1,82
  • 32% -1,96
  • 35% -2,19
  • 45% -2,95
  • 47% -3,13
  • 55% -3,91
  • 57% -4,15
  • 62% -4,82
  • 65% -5,18
  • 70% -5,92
  • 72% -6,23
  • 75% -6,72
  • 77% -7,05
  • 82% -7,84
  • 85% -8,29
  • 87% -8,60
  • 90% -9,03
  • 96% -9,88
  • 98% -10,27
  • 99% -10,57
  • 99,6% -10,92
  • 99,7% -11,01
  • 99,95% -11,64
  • 100.00% -11,94

So, not only the behaviour of 30% and 96% acid are different, but both are quite different from what happens at 70% or 100,00%.


[Edited on 15-3-2024 by chornedsnorkack]



...is that the density of each concentration of the acid?


The Hammett acidity function is essentially an extension of the pH scale into non-aqueous solvents.




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[*] posted on 15-3-2024 at 09:34


Quote: Originally posted by fx-991ex  
Am sorry to drift this off topic a little, but why the dioxide not react with sulfuric acid to make Mn(SO4)2?, i expect oxidizer to react with acid usually.

Did you mean oxide? Mn4+ is not much stable. Its only compounds that I know are our subject (MnO2) and MnF4, which is unstable and reacts with anything (air, water, solvents). Manganese likes to be 2+, that's why we need a reducing agent.

@solo: Those are the values in the Hammett acidity scale. It's like pH, for concentrated solutions. At low concentrations, the pH and Hammett values are very close. (Nevermind.)

[Edited on 15-3-2024 by bnull]




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[*] posted on 17-3-2024 at 02:37


Quote: Originally posted by fx-991ex  
Am sorry to drift this off topic a little, but why the dioxide not react with sulfuric acid to make Mn(SO4)2?, i expect oxidizer to react with acid usually.

[Edited on 15-3-2024 by fx-991ex]


It could react, but you need boiling concentrated, or maybe digestion ( long time medium temperature acid)

I think its because solubility of MnO2 is insoluble.


" Manganese (IV) dioxide (MnO2) is a strong oxidizer and is insoluble in water, nitric acid, or cold sulfuric acid, and it may slowly dissolve in aqueous HCl to give off Cl 2 gas."

Methods for converting manganese dioxide into water-soluble manganese salts
goggle patent. EP2930163A1






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[*] posted on 12-5-2024 at 12:26


Add the oxide to some water, slowly add sulphuric acid and hydrogen peroxide until you obtain a pink solution. Filter and then concentrate. You'll get MnSO4 1-Hydrate.

It is better to separate the crystals from mother liquors after a few hours at room temperature.
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