The reaction you've described involves several steps of chemical transformation. Here is a summary of the reactions involved:

Calcium carbonate $CaCO3$ is decomposed to form calcium oxide $CaO$.Calcium oxide $CaO$ reacts with carbon to form calcium carbide $CaC2$.Calcium carbide $CaC2$ reacts with water to produce acetylene gas $C2H2$.Acetylene gas $C2H2$ undergoes a series of reactions to form vinyl chloride $CH2=CHCl$.Vinyl chloride $CH2=CHCl$ polymerizes to form polyvinyl chloride $-CH2-CH-$n.Chlorine gas $Cl2$ is then used as a reactant in the polymerization process.

Overall, this reaction sequence involves the conversion of calcium carbonate to polyvinyl chloride through a series of chemical reactions.