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j_sum1
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So...
6H2O2 + Mo --> O2 + H2MoO4 + 5H2O??
Why not
4H2O2 + Mo --> H2MoO4 + 3H2O
Is it not correct to consider the evolution of O2 an undesired side reaction catslysed by the Mo? And just because I have bubbles evolving, that is no
indicator that I am actually dissolving my Mo.
Is the acetic acid doing nothing? I ask because I merely copied what was done upthread.
Nearly 48 hours and my wire is still there. This is depressingly slow.
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Mesa
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Molybdenum acetate only forms from molybdenum hexacarbonyl. Evolution of bubbles can only be one of two possibilities given whats in the reaction
mixture.
edit:
Yes, the acetic acid is doing nothing. Acetic acid/hydrogen peroxide has been used industrially to oxidize group 6 metals, but the concentrations
were essentially 1:1. The idea was that the peracid was a better oxidizer than the H2O2.
[Edited on 23-3-2015 by Mesa]
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Kitsune1
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Molybdenum Disulphide can be used as a catalyst in the decomposition of H2O (it has potential as a Pt replacement in Hydrogen Fuel Cells),
so it is plausible that there is some decomposition of H2O2 however this reaction is so painfully slow and so little gas is
actually evolved that it would be very hard to test.
My reason for the addition of Acetic Acid was purely to be in line with my other experiments which was to look at Acetate-metal complexes such as
Copper (ii) Acetate or Iron (iii) Oxyacetate. I was interested to see whether Molybdenum (as well as Tungsten) could be dissolved into an organic acid
in the same way that copper could through the simple action of a household oxidiser (H2O2) as a potential route to open up
further studies into Mo compounds without reliance on purchasing compounds or using reagents such as HF. However what made things more interesting for
me is that on the addition of Hydrogen Peroxide, Molybdic/Tungstic acid was created, not the respective acetate, thus rendering the addition of Acetic
Acid unnecessary.
I don't know whether Acetic acid's action on Mo(CO)6 is the only route or whether it is the standard route used as I have not looked into
Group 6 chemistry too much and the information out there seems very limited.
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bolbol
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Wouldn't Aqua regia (Nitric + Hydrchloric acid) get the job done?
I heard Ruthenium is the only metal that Aqua regia doesn't do anything against
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Kitsune1
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It does, especially in hot Aqua Regia, it will even react with hot Hydrochloric acid or Hot Sulphuric; Nitric acid can also dissolve it but it quickly
passivates; the aim was to bring the metal into solution without the use of "dangerous" reagents, really testing how far I could go with organic
acids. Ruthenium is indeed a strange metal, most room temperature or hot acids have no action on it but then it is vulnerable to to ClO-
ion.
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Molecular Manipulations
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Ref? A catalyst causes a reaction to proceed faster or slower (usually faster) then it otherwise would. It can't cause a thermodynamically unfavorable
reaction to proceed any more than it's own equilibrium would allow.
H2O(g) → H2 + 1/2 O2 ΔG°= 228.7 kJ/mol. For the opposite of this reaction (formation of water) the Keq
= 1.22x10^83 That's an enormous constant, no visible amount of water can decompose without adding the 228.7 kJ/mol, catalyst or not.
[Edited on 24-3-2015 by Molecular Manipulations]
-The manipulator
We are all here on earth to help others; what on earth the others are here for I don't know. -W. H. Auden
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Kitsune1
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Quote: Originally posted by Molecular Manipulations  |
Ref? A catalyst causes a reaction to proceed faster or slower (usually faster) then it otherwise would. It can't cause a thermodynamically unfavorable
reaction to proceed any more than it's own equilibrium would allow.
H2O(g) → H2 + 1/2 O2 ΔG°= 228.7 kJ/mol. For the opposite of this reaction (formation of water) the Keq
= 1.22x10^83 That's an enormous constant, no visible amount of water can decompose without adding the 228.7 kJ/mol, catalyst or not.
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The reference,
Gao, M.-R. et al. An efficient molybdenum disulfide/cobalt diselenide hybrid catalyst for electrochemical hydrogen generation. Nat. Commun.
6:5982 doi: 10.1038/ncomms6982 (2015).
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Molecular Manipulations
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And that's what I was expecting, electrochemical hydrogen generation. There's the energy source.
[Edited on 24-3-2015 by Molecular Manipulations]
-The manipulator
We are all here on earth to help others; what on earth the others are here for I don't know. -W. H. Auden
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