What products result from reacting lithium chloride and sulphuric acid?

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Offline chemistryrules

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Why does this reaction occur
LiCl +H2SO4 --> LiHSO4 + HCl

as opposed to...
2LiCl + H2SO4 --> Li2SO4 +2HCl  [V]

any help would be much appeciated!  [:)]
« Last Edit: 22/05/2011 23:12:09 by chris »

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Offline lightarrow

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Hint: is this reaction possible?

H+ + SO4-- --> HSO4-

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Offline damocles

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It is all to do with the quantities. Sulfuric acid is a liquid, and lithium chloride is a solid. If you do this reaction, the obvious thing is to use excess sulfuric acid so that the whole of the solid gets wet, and you have a reasonably uniform and workable mixture. With excess sulfuric acid you get

LiCl + H2SO4 --> LiHSO4 + HCl

But if you restrict the amount of sulfuric acid present -- perhaps by using a solution in another liquid that reacts with neither of the reactants* -- it is quite a straightforward matter to get

2 LiCl + H2SO4 --> Li2SO4 + 2 HCl.

However, if you try to react liquid sulfuric acid with an excess of solid lithium chloride, you will get a messy and non-uniform product containing a mixture of LiCl, LiHSO4, and Li2SO4, simply because there will not be enough liquid to wet all of the salt.

* trying to find a workable liquid that will dissolve but not react with sulfuric acid is not an easy task. A good quality kerosene or paraffin oil might do the trick
1 4 6 4 1
4 4 9 4 4     
a perfect perfect square square
6 9 6 9 6
4 4 9 4 4
1 4 6 4 1

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Offline lightarrow

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Another possible way to get Li2SO4 only is to mix LiCl and H2SO4 in stoichometric amounts according to:

2LiCl + H2SO4

and then increase the temperature to melt the reactants.

Explanation: LiHSO4 reacts quantitatively with LiCl without the need of water, in those conditions:

LiHSO4 + LiCl → Li2SO4 + HCl↑

« Last Edit: 24/06/2011 20:33:34 by lightarrow »