To answer my own question (because I have no life and the question lodged itself in my head until it drove me to find out the answer),
According to
http://www.icco.org/questions/density.htm,
The density of chocolate is 80 pounds per cubic foot.
A ton of chocolate will then occupy 25 cubic feet.
That would be a five foot cube.
If it was solid, that chocolate heart would be much smaller.
Of course, I'm no chocolate expert (as much as I love eating the stuff). Maybe it is made of some very light, frothy kind of chocolate that would take up more volume.