Agold coin contains 3.47*10^23 gold atoms. what is the mass of the coin in grams

Which statement about the stamps is correct?

Achemical reaction is done in the setup shown, resulting in a change of mass. what will happen if the same reaction is done in a sealed container that is placed on the electronic balance?

What does the field of thermodynamics relate to a-changes in nuclear reactions b- changes in energy in systems c changes in molecular structure d changes in atomic properties