Limestone stalactites and stalagmites are formed in caves by the following reaction: ca2+(aq)+2hco−3(aq)→caco3(s)+co2(g) +h2o(l) if 1 mol of caco3 forms at 298 k under 1 atm pressure, the reaction performs 2.49 kj of p−v work, pushing back the atmosphere as the gaseous co2 forms. at the same time, 38.90 kj of heat is absorbed from the environment.