What is the difference between thermal decomposition and combustion

Thermal decomposition refers to the formation of two or more products from a single reactant while combustion refers to reaction of a substance with oxygen to produce heat, light and other chemical substances.

Explanation:

An example of thermal decomposition is the formation of quick lime (calcium oxide)

CaCO3(s)> CaO(s) + CO2 (g)

heat

The two products were formed from a single reactant CaCO3

Combustion refers to the combination of a substance with oxygen, e.g, the combination of coke with oxygen:

C(s) + O2(g) > CO2(g)

Heat and light often accompany combustion reaction.

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.