binaryclock
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CuSO4 + NaHCO3 a bit of help please with products..
Can someone explain the reaction of copper(ii) sulfate and sodium bicarbonate to me? this is the accepted solution:
CuSO4 + 2NaHCO3 -> CuCO3 + CO2 + H2O + Na2SO4
I would of thought that the products would be CuCO4, and NaSO4.
Sorry for my ignorance, I'm reading tons about all this in different books just need a bit of help once in a while.
Thanks
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DraconicAcid
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You can't make CuCO4 or NaSO4. Both the carbonate ion (which has three oxygens) and the sulphate ion have a negative two
charge, so have to be balanced with cations that have a total charge of +2. One copper(II) ion will work, but sodium has a charge of +1, so you need
two of them.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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vmelkon
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You need to learn about cations and anions.
The charge on Cu is 2+.
The charge for SO4 is 2-.
Therefore copper sulfate is CuSO4.
Carbonate is CO3 with charge of 2-.
There is no such thing as CO4. Draw the anion and see for yourself.
Sodium sulfate is Na2SO4 because
The charge on Na is 1+.
The charge for SO4 is 2-.
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12AX7
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"CuCO4 and NaSO4" typo right?
The equation is correct.
Water can be ignored, since you usually do such a reaction in a huge excess of water to begin with. Also, the CO2 leaves fairly easily, but not
instantly, so it's of some consequence in the reaction.
Among the more subtle things which can happen:
- Copper forms a carbonate complex, meaning, copper is actually soluble in strong carbonate solutions -- not like calcium, for example, where you can
force more out of solution by Le Chatelier's principle.
- Copper does not (or doesn't normally) form a stable carbonate, but rather a basic carbonate, with some mixture of OH and CO3 present. As a result,
more CO2 will be given off than expected, particularly on boiling.
- CO2 and carbonate have a fairly slow reaction equilibrium, so to drive the reaction forward, you often heat the solution to speed it up. This also
reduces the solubility of CO2 in H2O, and pushes end products to more stable forms (perhaps resulting in a lower basic carbonate, i.e., with more OH
and less CO3 in it).
Tim
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bfesser
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Quote: Originally posted by bfesser  | In my experience, copper(II) sulfate will react with sodium bicarbonate, precipitating copper(II) bicarbonate (rxn. I), which quickly decomposes (rxn.
II) to copper(II) carbonate.<strong><ol type="I"><li>CuSO<sub>4</sub>(aq) + 2 NaHCO<sub>3</sub>(aq)
→ Cu(HCO<sub>3</sub> <sub>2</sub>(s) +
Na<sub>2</sub>SO<sub>4</sub>(aq)</li>
<li>Cu(HCO<sub>3</sub><sub>2</sub>(s) →
CuCO<sub>3</sub>(s) + CO<sub>2</sub>(g) + H<sub>2</sub>O</li></ol></strong |
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Hexavalent
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Where is the reference for this?
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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bfesser
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My original reference was an email I received from a university professor many years ago—lost to time, I think.
Here are a few documents I found with a <a href="http://scholar.google.com/" target="_blank">Google Scholar</a> <img
src="../scipics/_ext.png" /> search:
<strong><a href="http://dx.doi.org/10.1016/0043-1354(71)90049-2" target="_blank">Copper/bicarbonate equilibria in solutions of bicarbonate
ion at concentrations similar to those found in natural water</a></strong> <img src="../scipics/_ext.png" />
<strong><a
href="http://www.researchgate.net/publication/11682690_Complexation_of_Copper(II)_with_Carbonate_Ligands_in_Aqueous_Solution_A_CW_and_Pulse_EPR_Study/
file/79e4150ef416c86083.pdf" target="_blank">Complexation of copper (II) with carbonate ligands in aqueous solution: A cw and pulse EPR
study</a></strong> <img src="../scipics/_pdf.png" />
And I found this interesting paper while searching:
<strong><a href="http://libinfo.uark.edu/aas/issues/1941v1/v1a21.pdf" target="_blank">Crystals of an insoluble carbonate of copper grown
under a soda solution</a></strong> <img src="../scipics/_pdf.png" />
I probably should have just written it as one equation with two arrows, having the bicarbonate species in square brackets, to indicate an inferred
unstable species.
[Edited on 29.7.13 by bfesser]
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