But in some sources it was explained that stability of group 1 bicarbonates increases down the group.If it is true then how does lithium bicarbonate does not decompose ?.Can anyone please tell me stability order of both group 1 and group 2 carbonates and bicarbonates along with this question above.
5
-
$\begingroup$ Review the guide How to ask and Asking FAQs to prevent clarification requests, objections, downvoting or closure. $\endgroup$– PoutnikCommented Apr 29 at 11:17
-
$\begingroup$ You may find useful reviewing the targeted search results like site:stackexchange.com OR site:libretexts.org OR site:wikipedia.org bicarbonate stability $\endgroup$– PoutnikCommented Apr 29 at 11:37
-
1$\begingroup$ Consider that NaHCO3 is regularly sold as baking soda, but you cannot buy the same for Mg, Ca nor Li. // In a way, what does not exist as solid on the shelf, cannot decompose there. $\endgroup$– PoutnikCommented Apr 29 at 12:12
-
1$\begingroup$ Those who told you that "Group 2 bicarbonates do not decompose on heating" are wrong. For example calcium bicarbonate exists only in cold water. $\endgroup$– MauriceCommented Apr 29 at 12:45
-
$\begingroup$ See: chemistry.stackexchange.com/questions/97084/… $\endgroup$– Nilay GhoshCommented Apr 29 at 16:02
Add a comment
|
2 Answers
$\begingroup$
$\endgroup$
You may have misunderstood. Lithium and G2 metals, and for that matter most metals, do not form solid bicarbonates at all. We can have bicarbonate solutions of many metals in water, but except for sodium and heavier alkali metals evaporating the solvent will precipitate the carbonate or hydroxide instead of a proposed solid bicarbonate.
All such precipitates with metal cations, regardless of the anion you get, decompose upon heating. Sodium and heavier alkali metals, which actually give the solid bicarbonate, give off carbon dioxide and water from these bicarbonates to become the carbonate. The carbonate is stable against further heating (except, possibly, for losing water of hydration). The carbonates or hydroxides that precipitate from bicarbonate solutions of other metals, including lithium and G2 metals, decompose upon heating to give the metal oxide plus carbon dioxide or water.
Bicarbonates can also exist with some nonmetal cations, and thermal decomposition path may be different. Ammonium bicarbonate, for instances, breaks down on heating all the way to ammonia, carbon dioxide and water.
$\begingroup$
$\endgroup$
1
The correct statements should be:
- grp 1 carbonates and bicarbonates are stable except that of Li because it readily dissociates to Li2O and CO2.
- grp 2 carbonates and bicarbonates are not that stable and dissociate to metal oxides and CO2 on heating
- In both the grps, stability of carbonates and bicarbonates increase down the respective grps.
All of these statements are referred from NCERT books published in India.
-
$\begingroup$ Group 2 bicarbonates, like calcium bicarbonate, exist only in solution, and in cold solution. When heated or evaporated, they are transformed into carbonate and $\ce{CO2}$. The dissociation into oxide occurs only at high temperature (above $800$ °C) $\endgroup$– MauriceCommented Apr 29 at 16:02