What is the amount of energy required to convert one gram of mercury into gold?
The actual answer is that it would take an unbelievable amount of energy to convert one gram of mercury into gold. It would be such a large amount that I'm not even sure that it could be accurately calculated. Let me explain why below.
The only way to change one atom into a different atom is through nuclear chemistry. Because the atomic number of an atom (the number of protons in the nucleus) is what defines the identity of that atom, you have to either add to or subtract from the number of protons in that atom and the only way to do that is through nuclear chemistry. Since mercury (Hg) and gold (Au) sit right next to each other on the periodic table, it is possible to take an atom of mercury (atomic number = 80) and remove one of its protons to convert it into an atom of gold (atomic number = 79). Bombarding certain isotopes of mercury with neutrons will accomplish this nuclear conversion but it requires a lot of energy and can only produce a few atoms at a time. To actually produce one gram of gold by this method would require an enormous amount of time and energy and would cost much, much more that the current price of a gram of gold.