When limestone (which is principally CaCO3) is heated, carbon dioxide and quicklime
(Cao) are produced by the reaction
CaCO3(s) 4CaO(s) + CO2(g).
If 12.5 g of CO2 was produced from the ther-
mal decomposition of 40.79 g of CaCO3, what
is the percentage yield of the reaction?
Answer in units of %.

the correct answer is:

a. formation of precipitation

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.

i think its 5049.

i hope this !