2 NH4ClO4 + 8 Mg + energy ---> 8 MgO + N2 + 4 H2 + Cl2

MgCl₂ and H₂O seems much more likely.

MgCl₂ and H₂O seems much more likely.

Both! I made the reaction by myself (just by adding some magnesium powder to solid ammonium perchlorate in a porcelain dish) and both magnesium oxide and chloride were produced.

Yesterday I was a liitle bit to lazy to post results of my "investigation" into the problem. I am finishing work on the equation balancing program (some of you have already seen screenshots) and I am testing it whenever possible. Thus I have checked how this reaction can be balanced.

Lets start with Cotex approach:

2 NH₄ClO₄ + 8 Mg -> 8 MgO + N₂ + 4 H₂ + Cl₂

it is hot and there are hydrogen and free chlorine, so the first obvious change is

2 NH₄ClO₄ + 8 Mg -> 8 MgO + N₂ + 3 H₂ + 2HCl

MgO and HCl? Doesn't look like stable combination:

2 NH₄ClO₄ + 5 Mg -> 5 MgCl₂ + N₂ + 8HCl

However, there are also other possibilities, like:

2 NH₄ClO₄ + 4 Mg -> 4 MgO + N₂ + 4 H₂O + Cl₂

or

2 NH₄ClO₄ + 5 Mg -> 4 MgO + MgCl₂ + N₂ + 4 H₂O

I would say the last one seems the best to me, as there are no highly reactive substances between the products.

Probably in reality products of this reaction can be a mixture of all substances mentioned plus a few others, as a lot will depend on the reaction pathways and the circumstances - in open gases may be removed before they can react with other reagents, also in open oxygen from air may play some role. Some chlorine oxides, or traces of ammonia between products will also not rise a brow. At least my brow