The balanced chemical equation for the decomposition of potassium bromate upon heating is:

2KBrO3 (s) → 2KBr (s) + 3O2 (g)

In this reaction, potassium bromate (KBrO3) decomposes to form potassium bromide (KBr) and oxygen gas (O2). The oxygen gas is released as a product of the decomposition reaction.