Chocolate can kill a dog eventually but usually the chocolate poisoning won't happen really quick.
For chocolate to kill a dog the dog would have to ingest at least 20mg of theobromine or more before it led to chocolate poisoning.
However if a dog just ate a bite of chocolate it's unlikely it will cause any harm or death in the dog but if a dog does ingest enough chocolate it would likely take around a few days to a week and maybe even a month before the dog actually did die from the chocolate poisoning.
The signs of a dog that has chocolate poisoning usually appear within 12 to 72 hours after the dog ate the chocolate and most commonly the dog will vomit a lot.
If you think your dog has eaten too much chocolate then you should take the dog to the vet for treatment or else the dog may get sick and die.