Use standard enthalpies of formation to calculate ΔH∘rxn for the following reaction:? CaO(s)+CO2(g)→CaCO3(s)

The standard heat of reaction is -178.3 kJ.

We have the following information:

For most chemistry problems involving ##ΔH_f^"o"##, you need the following equation:

##ΔH_(rxn)^"o" = ΣΔH_f^"o"("p") - ΣΔH_f^"o"("r")##,

where ##"p"## = products and ##"r"## = reactants.

##ΣΔH_f^"o"("p") = 1 cancel("mol CaCO₃") × "-1206.9 kJ"/(1 cancel("mol CaCO₃")) = "-1206.9 kJ"##

##ΣΔH_f^"o"("r") = 1 cancel("mol CaO") × "-635.09 kJ"/(1cancel("mol CaO")) + "1 mol" cancel("CO₂") × "-393.509 kJ"/(1cancel("mol CO₂")) = "-1028.599 kJ"##

##ΔH_("rxn")^"o" = ΣΔH_f^"o"("p") - ΣΔH_f^"o"("r") = "-1206.9 kJ + 1028.599 kJ" = "-178.3 kJ"##