Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: INeedSerotonin on February 03, 2020, 01:18:46 PM
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Hello
I found this exercise:
Shellfish have a shell made of calcium carbonate, which is formed when calcium ions, secreted from shellfish cells, find sea water, which is rich in dissolved carbon dioxide.
One can say that
I - one of the reactions is Ca2+ + CO32- --> CaCO3
II - The reaction which involves the calcium ions while forming the shell is an acid-base reaction
III - the product is classified as an basic oxide
Which ones of these are true? Answer: only (I)
I think it should be (I) and (II), because CO32- has electrons to give, and Ca2+ misses electrons. So one donates to the other, making it a Lewis acid-base reaction.
Can you guys shed some light here?
Thank you
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Calcium carbonate is an ionic solid containing Ca2+ and CO32- ions. No Lewis acid-base reaction occurs.
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Thanks. I'm still confused, though.
Isn't AlCl3 + Cl- <--> AlCl4- an acid-base reaction too? Cl- is a base, right?
I don't get why my first reaction (Ca2+ + CO32-) cannot be an acid-base reaction too.
Perhaps it has something to do with having only ions, which makes it not be an acid-base reaction?
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The Cl- donates a pair of electrons to form an Al-Cl covalent bond. That does not happen in CaCO3. The ions are held together by coulombic attraction, not by electron donation and bond forming.