# Why does CaCO3 react with HCl, but not with H2SO4?

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?

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

$\ce{CaCO3}$ 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.