1
$\begingroup$

I know that $\ce{NaHCO3}$ is sodium bicarbonate, but According to Wikipedia:

In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, $\ce{CO3^{2-}}$.

$\ce{NaHCO3}$ also has the $\ce{CO3^{2-}}$ group, but is it a carbonate?

That is, are bicarbonates a subset of carbonates?

$\endgroup$
4
$\begingroup$

Carbonates are salts and esters of carbonic acid $\ce{H2CO3}$.

In generic nomenclature you may therefore consider a hydrogen carbonate also a subset of all carbonates. They are sometimes also referred to as primary carbonates.

Another considerable point is, that the structural subunit $\ce{O=C(-O-)2}$is still conserved.

In a stricter sense a hydrogencarbonate is only all forms involving $\ce{HCO3-}$, so it appears to be not a generic carbonate, but a class of its own. This refers to its one $\ce{O-H }$ bond and therefore it being a different structure.

However, another point of view should always consider aqueous solution equilibrium. \begin{aligned} \ce{HCO3- + H2O &<=> H3+O + \color{\red}{CO3^{2-}}}\\ \ce{HCO3- + H2O &<=> H2CO3 + {}^{-}OH} \end{aligned}

You can see that carbonate ions will be present to a certain extend in solution. The chemistry will therefore also to some extend resemble the chemistry of the carbonate.

Chemical properties of bicarbonate compound might differ from the pure carbonates - incorporation of water, solubility, ... .

On another page, in organic chemistry the compound class carbonates refers to structures of the type $\ce{\color{\red}{R}-{CO3}-\color{\navy}{R'}}$, where $\ce{\color{\red}{R},\color{\navy}{R'}$\in$ Alkyl, Aryl}$ - hence esters.

To sum it all up, since a more stringent definition of carbonate is not present to me, I would always consider a bicarbonate a carbonate.

| improve this answer | |
$\endgroup$
1
$\begingroup$

I would consider it a carbonate. Chemistry of sodium bicarbonate, or sodium hydrogen carbonate, or simply baking soda, is very similar to that of just sodium carbonate, or $\ce{Na_2CO_3}$.

Adding a strong acid to either $\ce{Na_2CO_3}$ or $\ce{NaHCO_3}$ will effect bubbling. Why? The acid protonates the carbonate or bicarbonate and forms the unstable $\ce{H_2CO_3}$, which is generally referred to as carbonic acid, but is in fact a mixture of carbonic acid and the much less potent acid, hydrated carbon dioxide. $\ce{H_2CO_3}$ decomposes rapidly to water and carbon dioxide. Hence, in the lab, if you wished to test for the present of carbonate in a salt, you could try adding a strong acid and look for bubbling. Copious bubbling is an indication of the presence of a carbonate or a carbonate derivative such as $\ce{HOCO_2^-}$ ($\ce{HCO3^-}$). To verify which carbonate you may simply perform a pH test as the $\ce{CO_3^2-}$ anion is a much strong base than the $\ce{HOCO_2^-}$ ion.

| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.