[shalikadm]

My tutor told that solid LiHCO₃ doesn't exist. I googled only to find that it exists in liquid form due to its unique structure.
Can someone explain it further ?
Thanks!

[Corribus]

We've discussed recently how the stability of carbonates decrease going down the group.

http://www.chemicalforums.com/index.php?topic=66412.msg239894#msg239894

Bicarbonate salts would be less stable than carbonates because the proton cation is the highest group there is.  Therefore lithium bicarbonate is only quasistable, only slightly more stable, I imagine, than carbonic acid, which spontaneously decomposes to water and carbon dioxide.  There's an entropic driving force to form carbon dioxide.

[shalikadm]

We've discussed recently how the stability of carbonates decrease going down the group.

It must be ;stability of carbonates increases down the group.am i correct?

The carbonates become more stable to heat as you go down the Group.

Thanks for response !

[Corribus]

Sorry, yes, that should read that carbonates become more stable as you go down the group.  That was an unfortunate typo.

[shalikadm]

Sorry, yes, that should read that carbonates become more stable as you go down the group.  That was an unfortunate typo.

I have found the same confusion there in the link you gave me to the the thread about stability of carbonates.

Oh that's right, in the separation of just the cation and the carbonate anion, the energy required to break the ionic lattice decreases as we go down the group. The last part in the link associated them very well

Thanks Corribus for the awesome help and also to BigDaddy for the enlightening question

What you meant by the "the highest group"

Bicarbonate salts would be less stable than carbonates because the proton cation is the highest group there is.

Does it mean being the top of the 1st group in periodic table ?
Does the whole thing implies some thing that when the cation is replaced by a proton, its thermodynamical stability decreases ?
Just take salts of phospate..
Does it will be less stable when going like , Na3PO4, Na2HPO4, NaH2PO4....?

[Corribus]

I'm doing a real great job with my terminology here, aren't I?  I meant - highest up on the periodic table.

That is:

Stability goes like this: H₂CO₂ < Li₂CO₂ < Na₂CO₂ < K₂CO₂ < Rb₂CO₂ < Cs₂CO₂.  In general, group 2 carbonates (Be, Mg, Ca, Sr, ...) are even less stable because the +2 charge is even more polarizing than the +1 charge in group 1 cations.  Group 2 bicarbonates don't even exist in solid form.

Bicarbonate is just a hybrid, where one of the lower-period cations is replaced by hydrogen.  So I'd expect lithium bicarbonate (LiHCO₃) to be intermediate in stability between H₂CO₃ and Li₂CO₃.  I don't have reaction enthalpies handy to prove that, but you can probably look them up somewhere.

[shalikadm]

Thanks very much Corribus !