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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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  • $\begingroup$ Have a look at these picures $\endgroup$ – K_P Feb 27 '16 at 20:11
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    $\begingroup$ Who said there is no reaction between $\ce{CaCO3}$ and $\ce{H2SO4}$? - chemiday.com/search/… $\endgroup$ – Nilay Ghosh Feb 28 '16 at 18:05
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    $\begingroup$ 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 Hollow Feb 28 '16 at 18:55
  • $\begingroup$ So, the reaction is theoretically possible but practically impossible..... $\endgroup$ – Nilay Ghosh Feb 29 '16 at 7:49
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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.

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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.

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