# Is lithium bicarbonate an aqueous solution of lithium carbonate?

This question is related to:

In the first question, the page from JD Lee (Concise Inorganic Chemistry 5 ed) states:

Lithium is exceptional that it does not form that it does not form a solid bicarbonate, though $\ce{LiHCO3}$ exists in solution. All the carbonates and bicarbonate are soluble in water.

and then in the sideline(the most important line):

If it exists in water, it must definitely be soluble in water.

Now, Lithium carbonate is prepared by bubbling $\ce{CO2}$ gas to a solution of lithium hydroxide, $\ce{LiOH}$.(source)

$$\ce{2LiOH + CO2 → (Li2CO3 + H2O)}$$

But in another source (endmemo), it shows that lithium hydroxide and carbon dioxide directly combines to form lithium bicarbonate.

$$\ce{LiOH + CO2 -> LiHCO3}$$

So, basically lithium bicarbonate is aqueous solution of lithium carbonate. Isn't it?

Now, what I gather from the fact that lithium carbonate is soluble in water and form a solution where the components do not react with each other. However, when the two reaction are compared, we observe that lithium carbonate reacts with water to form lithium bicarbonate. It seems contradictory with the above statement. How is this possible?

In the 3rd question, I said that if bromine reacts with water to form a mixture of acids, how can it be called a solution? Components of solution do not react with each other. Same case goes on with this reaction. If lithium carbonate is in aqueous solution, it should dissociate into component ions i.e $\ce{Li+}$ and $\ce{CO3^2-}$ but instead it goes on form $\ce{LiHCO3}$ and thus the solution has $\ce{Li+}$ and $\ce{HCO3-}$ ions. Why?

Lithium bicarbonate solution is something like a lithium carbonate solution in the sense that precipitation would produce the carbonate instead of the bicarbonate. But what is in solution is mostly lithium and bicarbonate ions. Precipitation is accompanied by a reaction in which the highly polarizing lithium ions react with bicarbonate:

$2\ce {Li+}+2\ce {HCO_3-}\rightarrow \ce {Li2CO_3}(s)+\ce {H2O}+\ce {CO2}$

Other alkali metals give less polarizing ions and do not react in the same way; they just precipitate the bicarbonate salt.

In a nutshell:

1. Depends how you define the solubility. The solubility product constants for lithium carbonate $\ce{Li2CO3}$ and magnesium carbonate $\ce{MgCO3}$ are $\ce{8.15×10^{-4}}$ and $\ce{6.82×10^{-6}}$ respectively. Thus, the solubility of magnesium carbonate in water at RT two orders of magnitude lower comparing to the solubility of lithium carbonate... approximately $\ce{0.014g/100ml}$ vs. $\ce{1.29g/100 mL}$.

2. It is a combination or synthesis reaction.

... basically lithium bicarbonate is aqueous solution of lithium carbonate.

Not really. It will be a mixture of lithium cations, carbonate and bicarbonate anions.

However, when the two reaction are compared, we observe that lithium carbonate reacts with water to form lithium bicarbonate. It seems contradictory with the above statement. How is this possible?

All salts of either weak base and/or weak acid will hydrolyze (react with water). For most cases its not important, thus no needs to complicate it. Where it is important, there is no need to name it, it is clear as it is. BTW what would be the proper name in your opinion?

1. The same logic - simplicity. That's why we have bromine water (: Can you come up with alternative names? Would be interesting to find out what do you have on your mind on this subject.