我想問石灰石岩洞同碳酸氫鈣有咩關係？ｃｈｅｍ老師入（２０分）

chalk, limestone, marble
all of these are mainly contain calcium carbonate

when acidic gas CO2 dissolve in rain water
acidic solution formed
CO2 + H2O → H2CO3 (reversible)

when this acidic solution in contact with CaCO3
CaCO3 + H2O + CO2 → Ca(HCO3)2
Ca(HCO3)2 is soluble in water
that is, CaCO3 will dissolves

limestone cave is formed when acidic rain water react with
chalk/limestone/marble which is underground
after the reaction
Ca(HCO3)2 is formed and chalk/limestone/marble dissolves
so a cave will be formed underground after a period of time

insoluble calcium carbonate, being a base, reacts with acids to form soluble calcium hydrogencarbonate and it dissolves into aqueous acidic solution,
CaCO3(s) + H+(aq) --> HCO3-(aq) + Ca2+(aq)
thus, rock containing calcium carbonate can be corroded by the prolonged exposure under acid rain