Does the reaction of sulfur and potassium nitrate involve production of sulfur trioxide?
Generally a mixture of sulfur, potassium nitrate with charcoal or an organic carbon compound is used in gunpowder mixture.

$$\ce{3C + S + 2KNO3 → 3CO2 + N2 + K2S}$$

(Source)

There are many questions in chem.SE related to gunpowder and explosives which are all based on this reaction. You can find them of help.


What is the oxidation mechanism of gunpowder?
What causes KNO3 to decompose into KNO2 and Oxygen in gunpowder?
Why can sulfur act like a catalyst?
Write the chemical equation of this reaction: