Chemistry - Why does CaCO3 react with HCl, but not with H2SO4?

Solution 1:

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.

Solution 2:

$\ce{CaCO3}$ 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.