Your dog is not going to die at all. The dog can eat white chocolate till it come out of its ears. Dairy milk chocolate he can have say half a small bar without to many ill effects. Though I would tend to keep all chocolate away from them.
The dark chocolate is the real problem all chocolate has an ingredient called Theobromine in it ,that can cause organ failure and death. But the dark chocolate is the one that carries the most.
This is from my website under poisons:
Dogs are particularly sensitive to a class of chemicals called methylxanthines. Theobromine and caffeine all belong to this family.
Dogs cannot metabolise and excrete these compounds as efficiently as humans. These compounds, once swallowed are taken up by the liver, transmitted back to the small intestine and converted back to the original methylxanthines.
After which, they take another trip around the body. This is repeated a number of times, so instead of getting rid of the compounds (as a human being does) the dog will just keep poisoning itself.
The difficulty is that there are many different formulations of chocolate, from sweet milk chocolate, which is the mildest form to the dark bitter chocolate, commonly produced for the continental market, but increasingly consumed in the UK.
A lethal amount of sweet milk chocolate is said to be around two ounces to every Kg in bodyweight. For example: A dog weighing 22lb the lethal amount would be around 20 ounces.
Dark bitter chocolate is considered to be about ten times as toxic, so a 22lb dog could actually die from as little as 2 ounces of dark chocolate.
The amount your dog has ingested is of no concern at all. Ignore the Trolls below that are trying to frighten you, they are idiots.
Dog Behaviourist UK