1
$\begingroup$

So I'm doing an investigation, and it involves using supersaturated solutions of Ca(OH)2 and of Sr(OH)2. I notice that there's always a flaky precipitate formed on top. I need to know about the reactions with carbon dioxide. Is it carbonate that's formed? Or is it hydrogen carbonate? Why?

$\endgroup$
  • $\begingroup$ In my opinion nothing prevents both carbonates and bicarbonates from forming those flakes on the surface; out of curiosity, why is it so crucial to determine which one is it? $\endgroup$ – andselisk Mar 17 at 12:33
  • 1
    $\begingroup$ Although knowing the identity of the precipitate is not really significant to my results in any ways, it's very important that I discuss it since the investigation is for my IB Chemistry Extended Essay. I am required to discuss basically everything going on in the solution in as much detail as possible. I just thought I'd probably be marked down if it I had no idea what's going on in my solutions.. $\endgroup$ – Mohamad Mar 17 at 12:36
  • $\begingroup$ Interesting, I didn't think of the possibility that it's both. Could be. Thanks! $\endgroup$ – Mohamad Mar 17 at 12:37
  • $\begingroup$ it is calcium carbonate that is forming. $\endgroup$ – Nilay Ghosh Mar 17 at 17:15
1
$\begingroup$

Your solid is the respective carbonate. Group II bicarbonates can form aqueous solutions, but do not form stable solids, ergo the solid flakes must be carbonate and formed along the lines of:

$$\ce{Ca(OH)2 (aq)+ 2CO2 (aq/g) <=> Ca^2+ + 2(HCO3)- (aq) <=> CaCO3 (s) + CO2 (aq/g)}$$

$\endgroup$

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.