mass and chemical reactions

[pixel01]

Does mass of compounds change due to exothermic/endothermic chemical reactions?

[malawi_glenn]

This is not the chemistry sub-forum *hint* ;-)

[mathman]

Does mass of compounds change due to exothermic/endothermic chemical reactions?

Yes but. The difference in mass is undetectable by almost all instruments.

[pixel01]

This is not the chemistry sub-forum *hint* ;-)

Chemically, the answer is definitely NOT, that's why I ask here.

[malawi_glenn]

Well chemistry processes are that the electrons are chaning orbits, so that their binding energy is released or increased -> which influences the mass of the system under consideration. It is the EM- force analogy with fusion and fission in Nuclear physics.

But the binding energies of electrons in atoms and molecules are of the order eV (!) so it is very tiny mass defect, just as mathman said.
The binding energies in nuclei are of the order MeV, so there the consequenses are bigger.