I have a wonderful reaction of marble chips, $\ce{CaCO3}$, with hydrochloric acid, $\ce{HCl}$, and carbon dioxide was released beautifully (fast, large volume, easy to measure and makes good visual effect too). But there is no reaction between $\ce{CaCO3}$ and $\ce{H2SO4}$. Why not?
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asked Feb 27, 2016 at 14:49
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$\begingroup$ Have a look at these picures $\endgroup$– K_PFeb 27, 2016 at 20:11
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4$\begingroup$ Who said there is no reaction between $\ce{CaCO3}$ and $\ce{H2SO4}$? - chemiday.com/search/… $\endgroup$– Nilay GhoshFeb 28, 2016 at 18:05
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4$\begingroup$ I actually observed a reaction for maybe 2-3 seconds both times I tried to do it. So I take it back that there is no reaction. It just stops extremely soon when protective layer of CaSO4 is formed. $\endgroup$– Sleepy HollowFeb 28, 2016 at 18:55
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$\begingroup$ So, the reaction is theoretically possible but practically impossible..... $\endgroup$– Nilay GhoshFeb 29, 2016 at 7:49
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2 Answers
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Your marble chips react on the surface.
In the case of hydrochloric acid, the resulting salt, calcium chloride, is highly soluble in the acid, dissolves and provides further attack to the (new) surface.
With sulfuric acid, the highly insoluble calcium sulfate is formed on the surface of the marble chip. With other words:
Calcium sulfate acts like a protective layer.
answered Feb 27, 2016 at 14:59
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$\ce{CaCO3}$ reacts with $\ce{H2SO4}$ but he reaction does not go further due to the formation of the layer of $\ce{CaSO4}$ on the surface of $\ce{CaCO3}$. If we scratch the surface the reaction will proceed in the forward direction.
