Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: chemistryrules on 21/05/2011 12:15:06

Title: What products result from reacting lithium chloride and sulphuric acid?
Post by: chemistryrules on 21/05/2011 12:15:06

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

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

any help would be much appeciated!  [:)]

Title: Re: What products result from reacting lithium chloride and sulphuric acid?
Post by: lightarrow on 21/05/2011 14:03:56

Hint: is this reaction possible?

H+ + SO4-- --> HSO4-

Title: What products result from reacting lithium chloride and sulphuric acid?
Post by: damocles on 22/06/2011 13:50:04

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

Title: What products result from reacting lithium chloride and sulphuric acid?
Post by: lightarrow on 22/06/2011 19:18:39

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↑