In a action, if the bonds in the reactants are stronger than the bonds in the product, what type of reaction is it?

1 Answer
Nov 19, 2016

It will be classified as an #"endothermic reaction."#


For our earliest exposure to physical chemistry, we are told that the formation of bonds releases energy, whereas the breaking of bonds requires energy. The balance between bond-making and bond-breaking determines whether a reaction will be exothermic #"(energy out)"# or endothermic #"(energy in)"#.

For a combustion reaction, typically we make strong bonds with respect to the product formed, cf:

#C(s) + O_2(g) rarr CO_2(g) + Delta#

In this reaction, we break strong #O=O#, and moderately strong #C-C# bonds, but we make VERY strong #C=O# bonds as carbon dioxide is produced. Certainly we can use this approach quantitatively, and determine how much heat, i.e. how much energy, we can get from combustion of a given quantity of carbon. How? Well, we can estimate very precisely the energy involved in bond fission or fusion, and these energies are extensively tabulated.

In your reaction, you have proposed breaking strong #"reactant"# bonds, and forming weaker #"product"# bonds. Given the demands of bond-breaking versus bond-making, your reaction will necessarily be #"endothermic"#.