Which reaction type would you classify PbCO3(s) -> 2PbO(s) + CO2(g)?

The reaction where lead(II) carbonate, PbCO3, decomposes into lead(II) oxide, PbO, and carbon dioxide, CO2, is classified as a decomposition reaction. In a decomposition reaction, a single compound breaks down into two or more simpler products. This is precisely what occurs in this case, as the single reactant PbCO3 breaks down to produce two distinct products: PbO and CO2.

Decomposition reactions often require an input of energy, such as heat, light, or electricity, to break the chemical bonds within the compound. The formation of two products from one reactant reinforces the classification of this reaction type. The other types listed involve the combination of substances or exchanges between reactants, which do not apply here, as there is no formation of a new compound or exchange of components involved in the reaction provided.