[beheada]

The reaction between Mercury and Sulfuric acid at a certain temperature causes the evolution of gas as well as a snow-white precipitate. I was sitting here trying to figure out how this occurred, but I can't balance out the equation so that it makes sense?

Hg + H2SO4 ----> HgSO4 (the precipitate?) + H2(g) The gas?

Naturally since sulfuric acid is a strong acid it should break up completely into its ions, but since its diprotic doesn't that make it H+ and HSO4? What would be the correct equation and what is the gas, because I seriously doubt it's Hydrogen?

[jdurg]

What concentration was the sulfuric acid?  Mercury metal will react with concentrated sulfuric acid to form HgSO4 (which is a white powder) and hydrogen gas.

[beheada]

It is concentrated sulfuric acid, I'm not sure of the exact concentration though.
So, I'm assuming that my original equation was in fact, correct?

Hg(s) + H₂SO₄(aq) ---> HSO₄(s) + H₂(g)

If this is the case, is what's left in the beaker excess sulfuric acid that hadn't reacted with the mercury? If I added equimolar amounts of mercury and sulfuric acid, theoretically there would be nothing left but the precipitate and evolved gas? (I guess that depends on the concentration of acid)

I'll have to do a titration to find out the concentration of the acid.

[jdurg]

Yes, you would be correct then.  If you take mercury metal and place it in concentrated (about 98%) H2SO4 and heat up the mixture, the acid will "eat away" at the mercury and form HgSO4 and hydrogen gas.  Anything left over would be excess H2SO4.

[woelen]

Yes, you would be correct then.  If you take mercury metal and place it in concentrated (about 98%) H2SO4 and heat up the mixture, the acid will "eat away" at the mercury and form HgSO4 and hydrogen gas.  Anything left over would be excess H2SO4.

Jdurg, I do not agree with you that hydrogen gas is formed. In reality, SO2 is formed, when concentrated H2SO4 is reacting with copper, mercury, or silver:

Hg + 2H2SO4 --> HgSO4 + SO2 + 2H2O

I'm not sure whether the mercury (I) or mercury (II) salt is formed. It might also be

2Hg + 2H2SO4 --> Hg2SO4 + SO2 + 2H2O, but I think it is the first one.

What I am sure about though is that the gas, which is formed is not H2, but SO2.

[beheada]

Ha ha, hence the question. Someone told me that it was SO₂ produced but I couldn't figure out what equation it would be. The gas produced definitely doesn't look like hydrogen, but is instead a thick cloudy white smoke. So I believe woelen to be correct on this as well, with the first equation at least.

Does anybody know what happens to HgSO₄ when you put it into H₂O. I believe a basic sulfate is formed (which would be the white solid turning into a yellow solid) and then mercury ion floats freely in solution?

So in this instance, the HgSO4 crystals/H2SO4 acid are transferred in solution where the acid breaks apart into its ions along with the Hg and the sulfate becomes its own solid?

My physical observations are simply that there is small gas evolution poured into water and the white solid turns yellow.

Is what's happening correct?

[P-man]

Could this porve to become a good way to make Hydrogen???

[beheada]

Negative.

It's SO₂ produced. Hydrogen gas looks and smells a whole lot different, and this gas is a thick white choking vapor (characteristic of SO2). So tragically, no hydrogen production.

Ironically, I have heard of recent developments in using enzymes as catalytic coating for the anodes/cathodes of electrolysis cells, which could replace the use of platinum thereby reducing the expense vastly.

http://www.newscientist.com/article.ns?id=dn3539

[woelen]

My physical observations are simply that there is small gas evolution poured into water and the white solid turns yellow.

Is what's happening correct?

What happens, happens! Whether you find it correct or not is a question which has no sense. It just happens  .

Hg(2+) ions are very prone to hydrolysis. The yellow color you have is the color of HgO/Hg(OH)2 (better: HgO.nH2O, hydrous mercury oxide). Without a coordinating ligand, like Cl(-) ions, Hg(2+) really easily is hydrolysed, with the formation of acid as a side reaction. It surprises me, however, that the white crystalline
mass shows hydrolysis to such extent, because they are still wetted with H2SO4.

The small bubbling most likely does not tell very much. It might be due to small bubbles of air, trapped in the solid, or small amounts of dissolved gas, driven out of the water. When you dissolve solids in water, it is quite common to see faint bubbles of dissolved air, which are expelled by the ionic compound.

[deyicheng]

Yes, you would be correct then.  If you take mercury metal and place it in concentrated (about 98%) H2SO4 and heat up the mixture, the acid will "eat away" at the mercury and form HgSO4 and hydrogen gas.  Anything left over would be excess H2SO4.

Jdurg, I do not agree with you that hydrogen gas is formed. In reality, SO2 is formed, when concentrated H2SO4 is reacting with copper, mercury, or silver:

Hg + 2H2SO4 --> HgSO4 + SO2 + 2H2O

I'm not sure whether the mercury (I) or mercury (II) salt is formed. It might also be

2Hg + 2H2SO4 --> Hg2SO4 + SO2 + 2H2O, but I think it is the first one.

What I am sure about though is that the gas, which is formed is not H2, but SO2.

i agree with you.H2 is impossible to give.